Adding upstream version 0.6.0.upstream/0.6.0

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

14 files changed, 5738 insertions, 0 deletions

diff --git a/src/Makefile.in b/src/Makefile.in
new file mode 100644
index 0000000..0d84e76
--- /dev/null
+++ b/src/Makefile.in
@@ -0,0 +1,64 @@
+.PHONY: clean distribution
+
+include @BUILD_DIR@/build/ck.build
+
+TARGET_DIR=$(BUILD_DIR)/src
+SDIR=$(SRC_DIR)/src
+INCLUDE_DIR=$(SRC_DIR)/include
+
+OBJECTS=ck_barrier_centralized.o	\
+	ck_barrier_combining.o		\
+	ck_barrier_dissemination.o	\
+	ck_barrier_tournament.o		\
+	ck_barrier_mcs.o		\
+	ck_epoch.o			\
+	ck_ht.o				\
+	ck_hp.o				\
+	ck_hs.o				\
+	ck_rhs.o			\
+	ck_array.o
+
+all: $(ALL_LIBS)
+
+libck.so: $(OBJECTS)
+	$(LD) $(LDFLAGS) -o $(TARGET_DIR)/libck.so $(OBJECTS)
+
+libck.a: $(OBJECTS)
+	ar rcs $(TARGET_DIR)/libck.a $(OBJECTS)
+
+ck_array.o: $(INCLUDE_DIR)/ck_array.h $(SDIR)/ck_array.c
+	$(CC) $(CFLAGS) -c -o $(TARGET_DIR)/ck_array.o $(SDIR)/ck_array.c
+
+ck_epoch.o: $(INCLUDE_DIR)/ck_epoch.h $(SDIR)/ck_epoch.c $(INCLUDE_DIR)/ck_stack.h
+	$(CC) $(CFLAGS) -c -o $(TARGET_DIR)/ck_epoch.o $(SDIR)/ck_epoch.c
+
+ck_hs.o: $(INCLUDE_DIR)/ck_hs.h $(SDIR)/ck_hs.c
+	$(CC) $(CFLAGS) -c -o $(TARGET_DIR)/ck_hs.o $(SDIR)/ck_hs.c
+
+ck_rhs.o: $(INCLUDE_DIR)/ck_rhs.h $(SDIR)/ck_rhs.c
+	$(CC) $(CFLAGS) -c -o $(TARGET_DIR)/ck_rhs.o $(SDIR)/ck_rhs.c
+
+ck_ht.o: $(INCLUDE_DIR)/ck_ht.h $(SDIR)/ck_ht.c
+	$(CC) $(CFLAGS) -c -o $(TARGET_DIR)/ck_ht.o $(SDIR)/ck_ht.c
+
+ck_hp.o: $(SDIR)/ck_hp.c $(INCLUDE_DIR)/ck_hp.h $(INCLUDE_DIR)/ck_stack.h
+	$(CC) $(CFLAGS) -c -o $(TARGET_DIR)/ck_hp.o $(SDIR)/ck_hp.c
+
+ck_barrier_centralized.o: $(SDIR)/ck_barrier_centralized.c
+	$(CC) $(CFLAGS) -c -o $(TARGET_DIR)/ck_barrier_centralized.o $(SDIR)/ck_barrier_centralized.c
+
+ck_barrier_combining.o: $(SDIR)/ck_barrier_combining.c
+	$(CC) $(CFLAGS) -c -o $(TARGET_DIR)/ck_barrier_combining.o $(SDIR)/ck_barrier_combining.c
+
+ck_barrier_dissemination.o: $(SDIR)/ck_barrier_dissemination.c
+	$(CC) $(CFLAGS) -c -o $(TARGET_DIR)/ck_barrier_dissemination.o $(SDIR)/ck_barrier_dissemination.c
+
+ck_barrier_tournament.o: $(SDIR)/ck_barrier_tournament.c
+	$(CC) $(CFLAGS) -c -o $(TARGET_DIR)/ck_barrier_tournament.o $(SDIR)/ck_barrier_tournament.c
+
+ck_barrier_mcs.o: $(SDIR)/ck_barrier_mcs.c
+	$(CC) $(CFLAGS) -c -o $(TARGET_DIR)/ck_barrier_mcs.o $(SDIR)/ck_barrier_mcs.c
+
+clean:
+	rm -rf $(TARGET_DIR)/*.dSYM $(TARGET_DIR)/*~ $(TARGET_DIR)/*.o \
+		$(OBJECTS) $(TARGET_DIR)/libck.a $(TARGET_DIR)/libck.so
diff --git a/src/ck_array.c b/src/ck_array.c
new file mode 100644
index 0000000..35b2502
--- /dev/null
+++ b/src/ck_array.c
@@ -0,0 +1,240 @@
+/*
+ * Copyright 2013-2015 Samy Al Bahra
+ * Copyright 2013-2014 AppNexus, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <ck_array.h>
+#include <ck_cc.h>
+#include <ck_pr.h>
+#include <ck_stdbool.h>
+#include <ck_string.h>
+
+static struct _ck_array *
+ck_array_create(struct ck_malloc *allocator, unsigned int length)
+{
+	struct _ck_array *active;
+
+	active = allocator->malloc(sizeof(struct _ck_array) + sizeof(void *) * length);
+	if (active == NULL)
+		return NULL;
+
+	active->n_committed = 0;
+	active->length = length;
+
+	return active;
+}
+
+bool
+ck_array_init(struct ck_array *array, unsigned int mode, struct ck_malloc *allocator, unsigned int length)
+{
+	struct _ck_array *active;
+
+	(void)mode;
+
+	if (allocator->realloc == NULL ||
+	    allocator->malloc == NULL ||
+	    allocator->free == NULL ||
+	    length == 0)
+		return false;
+
+	active = ck_array_create(allocator, length);
+	if (active == NULL)
+		return false;
+
+	array->n_entries = 0;
+	array->allocator = allocator;
+	array->active = active;
+	array->transaction = NULL;
+	return true;
+}
+
+bool
+ck_array_put(struct ck_array *array, void *value)
+{
+	struct _ck_array *target;
+	unsigned int size;
+
+	/*
+	 * If no transaction copy has been necessary, attempt to do in-place
+	 * modification of the array.
+	 */
+	if (array->transaction == NULL) {
+		target = array->active;
+
+		if (array->n_entries == target->length) {
+			size = target->length << 1;
+
+			target = array->allocator->realloc(target,
+			    sizeof(struct _ck_array) + sizeof(void *) * array->n_entries,
+			    sizeof(struct _ck_array) + sizeof(void *) * size,
+			    true);
+
+			if (target == NULL)
+				return false;
+
+			ck_pr_store_uint(&target->length, size);
+
+			/* Serialize with respect to contents. */
+			ck_pr_fence_store();
+			ck_pr_store_ptr(&array->active, target);
+		}
+
+		target->values[array->n_entries++] = value;
+		return true;
+	}
+
+	target = array->transaction;
+	if (array->n_entries == target->length) {
+		size = target->length << 1;
+
+		target = array->allocator->realloc(target,
+		    sizeof(struct _ck_array) + sizeof(void *) * array->n_entries,
+		    sizeof(struct _ck_array) + sizeof(void *) * size,
+		    true);
+
+		if (target == NULL)
+			return false;
+
+		target->length = size;
+		array->transaction = target;
+	}
+
+	target->values[array->n_entries++] = value;
+	return false;
+}
+
+int
+ck_array_put_unique(struct ck_array *array, void *value)
+{
+	unsigned int i, limit;
+	void **v;
+
+	limit = array->n_entries;
+	if (array->transaction != NULL) {
+		v = array->transaction->values;
+	} else {
+		v = array->active->values;
+	}
+
+	for (i = 0; i < limit; i++) {
+		if (v[i] == value)
+			return 1;
+	}
+
+	return -!ck_array_put(array, value);
+}
+
+bool
+ck_array_remove(struct ck_array *array, void *value)
+{
+	struct _ck_array *target;
+	unsigned int i;
+
+	if (array->transaction != NULL) {
+		target = array->transaction;
+
+		for (i = 0; i < array->n_entries; i++) {
+			if (target->values[i] == value) {
+				target->values[i] = target->values[--array->n_entries];
+				return true;
+			}
+		}
+
+		return false;
+	}
+
+	target = array->active;
+
+	for (i = 0; i < array->n_entries; i++) {
+		if (target->values[i] == value)
+			break;
+	}
+
+	if (i == array->n_entries)
+		return false;
+
+	/* If there are pending additions, immediately eliminate the operation. */
+	if (target->n_committed != array->n_entries) {
+		ck_pr_store_ptr(&target->values[i], target->values[--array->n_entries]);
+		return true;
+	}
+
+	/*
+	 * The assumption is that these allocations are small to begin with.
+	 * If there is no immediate opportunity for transaction, allocate a
+	 * transactional array which will be applied upon commit time.
+	 */
+	target = ck_array_create(array->allocator, array->n_entries);
+	if (target == NULL)
+		return false;
+
+	memcpy(target->values, array->active->values, sizeof(void *) * array->n_entries);
+	target->length = array->n_entries;
+	target->n_committed = array->n_entries;
+	target->values[i] = target->values[--array->n_entries];
+
+	array->transaction = target;
+	return true;
+}
+
+bool
+ck_array_commit(ck_array_t *array)
+{
+	struct _ck_array *m = array->transaction;
+
+	if (m != NULL) {
+		struct _ck_array *p;
+
+		m->n_committed = array->n_entries;
+		ck_pr_fence_store();
+		p = array->active;
+		ck_pr_store_ptr(&array->active, m);
+		array->allocator->free(p, sizeof(struct _ck_array) +
+		    p->length * sizeof(void *), true);
+		array->transaction = NULL;
+
+		return true;
+	}
+
+	ck_pr_fence_store();
+	ck_pr_store_uint(&array->active->n_committed, array->n_entries);
+	return true;
+}
+
+void
+ck_array_deinit(struct ck_array *array, bool defer)
+{
+
+	array->allocator->free(array->active,
+	    sizeof(struct _ck_array) + sizeof(void *) * array->active->length, defer);
+
+	if (array->transaction != NULL) {
+		array->allocator->free(array->transaction,
+		    sizeof(struct _ck_array) + sizeof(void *) * array->transaction->length, defer);
+	}
+
+	array->transaction = array->active = NULL;
+	return;
+}
diff --git a/src/ck_barrier_centralized.c b/src/ck_barrier_centralized.c
new file mode 100644
index 0000000..ca8cc18
--- /dev/null
+++ b/src/ck_barrier_centralized.c
@@ -0,0 +1,59 @@
+/*
+ * Copyright 2011-2015 Samy Al Bahra.
+ * Copyright 2011 David Joseph.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <ck_barrier.h>
+#include <ck_pr.h>
+
+void
+ck_barrier_centralized(struct ck_barrier_centralized *barrier,
+    struct ck_barrier_centralized_state *state,
+    unsigned int n_threads)
+{
+	unsigned int sense, value;
+
+	/*
+	 * Every execution context has a sense associated with it.
+	 * This sense is reversed when the barrier is entered. Every
+	 * thread will spin on the global sense until the last thread
+	 * reverses it.
+	 */
+	sense = state->sense = ~state->sense;
+	value = ck_pr_faa_uint(&barrier->value, 1);
+	if (value == n_threads - 1) {
+		ck_pr_store_uint(&barrier->value, 0);
+		ck_pr_fence_memory();
+		ck_pr_store_uint(&barrier->sense, sense);
+		return;
+	}
+
+	ck_pr_fence_atomic_load();
+	while (sense != ck_pr_load_uint(&barrier->sense))
+		ck_pr_stall();
+
+	ck_pr_fence_acquire();
+	return;
+}
diff --git a/src/ck_barrier_combining.c b/src/ck_barrier_combining.c
new file mode 100644
index 0000000..3ee72fd
--- /dev/null
+++ b/src/ck_barrier_combining.c
@@ -0,0 +1,207 @@
+/*
+ * Copyright 2011-2015 Samy Al Bahra.
+ * Copyright 2011 David Joseph.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <ck_barrier.h>
+#include <ck_cc.h>
+#include <ck_pr.h>
+#include <ck_spinlock.h>
+
+struct ck_barrier_combining_queue {
+	struct ck_barrier_combining_group *head;
+	struct ck_barrier_combining_group *tail;
+};
+
+CK_CC_INLINE static struct ck_barrier_combining_group *
+ck_barrier_combining_queue_dequeue(struct ck_barrier_combining_queue *queue)
+{
+	struct ck_barrier_combining_group *front = NULL;
+
+	if (queue->head != NULL) {
+		front = queue->head;
+		queue->head = queue->head->next;
+	}
+
+	return front;
+}
+
+CK_CC_INLINE static void
+ck_barrier_combining_insert(struct ck_barrier_combining_group *parent,
+    struct ck_barrier_combining_group *tnode,
+    struct ck_barrier_combining_group **child)
+{
+
+	*child = tnode;
+	tnode->parent = parent;
+
+	/*
+	 * After inserting, we must increment the parent group's count for
+	 * number of threads expected to reach it; otherwise, the
+	 * barrier may end prematurely.
+	 */
+	parent->k++;
+	return;
+}
+
+/*
+ * This implementation of software combining tree barriers
+ * uses level order traversal to insert new thread groups
+ * into the barrier's tree. We use a queue to implement this
+ * traversal.
+ */
+CK_CC_INLINE static void
+ck_barrier_combining_queue_enqueue(struct ck_barrier_combining_queue *queue,
+    struct ck_barrier_combining_group *node_value)
+{
+
+	node_value->next = NULL;
+	if (queue->head == NULL) {
+		queue->head = queue->tail = node_value;
+		return;
+	}
+
+	queue->tail->next = node_value;
+	queue->tail = node_value;
+
+	return;
+}
+
+
+void
+ck_barrier_combining_group_init(struct ck_barrier_combining *root,
+    struct ck_barrier_combining_group *tnode,
+    unsigned int nthr)
+{
+	struct ck_barrier_combining_group *node;
+	struct ck_barrier_combining_queue queue;
+
+	queue.head = queue.tail = NULL;
+
+	tnode->k = nthr;
+	tnode->count = 0;
+	tnode->sense = 0;
+	tnode->left = tnode->right = NULL;
+
+	/*
+	 * Finds the first available node for linkage into the combining
+	 * tree. The use of a spinlock is excusable as this is a one-time
+	 * initialization cost.
+	 */
+	ck_spinlock_fas_lock(&root->mutex);
+	ck_barrier_combining_queue_enqueue(&queue, root->root);
+	while (queue.head != NULL) {
+		node = ck_barrier_combining_queue_dequeue(&queue);
+
+		/* If the left child is free, link the group there. */
+		if (node->left == NULL) {
+			ck_barrier_combining_insert(node, tnode, &node->left);
+			goto leave;
+		}
+
+		/* If the right child is free, link the group there. */
+		if (node->right == NULL) {
+			ck_barrier_combining_insert(node, tnode, &node->right);
+			goto leave;
+		}
+
+		/*
+		 * If unsuccessful, try inserting as a child of the children of the
+		 * current node.
+		 */
+		ck_barrier_combining_queue_enqueue(&queue, node->left);
+		ck_barrier_combining_queue_enqueue(&queue, node->right);
+	}
+
+leave:
+	ck_spinlock_fas_unlock(&root->mutex);
+	return;
+}
+
+void
+ck_barrier_combining_init(struct ck_barrier_combining *root,
+    struct ck_barrier_combining_group *init_root)
+{
+
+	init_root->k = 0;
+	init_root->count = 0;
+	init_root->sense = 0;
+	init_root->parent = init_root->left = init_root->right = NULL;
+	ck_spinlock_fas_init(&root->mutex);
+	root->root = init_root;
+	return;
+}
+
+static void
+ck_barrier_combining_aux(struct ck_barrier_combining *barrier,
+    struct ck_barrier_combining_group *tnode,
+    unsigned int sense)
+{
+
+	/*
+	 * If this is the last thread in the group, it moves on to the parent group.
+	 * Otherwise, it spins on this group's sense.
+	 */
+	if (ck_pr_faa_uint(&tnode->count, 1) == tnode->k - 1) {
+		/*
+		 * If we are and will be the last thread entering the barrier for the
+		 * current group then signal the parent group if one exists.
+		 */
+		if (tnode->parent != NULL)
+			ck_barrier_combining_aux(barrier, tnode->parent, sense);
+
+		/*
+		 * Once the thread returns from its parent(s), it reinitializes the group's
+		 * arrival count and signals other threads to continue by flipping the group
+		 * sense. Order of these operations is not important since we assume a static
+		 * number of threads are members of a barrier for the lifetime of the barrier.
+		 * Since count is explicitly reinitialized, it is guaranteed that at any point
+		 * tnode->count is equivalent to tnode->k if and only if that many threads
+		 * are at the barrier.
+		 */
+		ck_pr_store_uint(&tnode->count, 0);
+		ck_pr_fence_store();
+		ck_pr_store_uint(&tnode->sense, ~tnode->sense);
+	} else {
+		ck_pr_fence_memory();
+		while (sense != ck_pr_load_uint(&tnode->sense))
+			ck_pr_stall();
+	}
+
+	return;
+}
+
+void
+ck_barrier_combining(struct ck_barrier_combining *barrier,
+    struct ck_barrier_combining_group *tnode,
+    struct ck_barrier_combining_state *state)
+{
+
+	ck_barrier_combining_aux(barrier, tnode, state->sense);
+
+	/* Reverse the execution context's sense for the next barrier. */
+	state->sense = ~state->sense;
+	return;
+}
diff --git a/src/ck_barrier_dissemination.c b/src/ck_barrier_dissemination.c
new file mode 100644
index 0000000..df151d8
--- /dev/null
+++ b/src/ck_barrier_dissemination.c
@@ -0,0 +1,130 @@
+/*
+ * Copyright 2011-2015 Samy Al Bahra.
+ * Copyright 2011 David Joseph.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <ck_barrier.h>
+#include <ck_cc.h>
+#include <ck_pr.h>
+#include <ck_spinlock.h>
+
+#include "ck_internal.h"
+
+void
+ck_barrier_dissemination_init(struct ck_barrier_dissemination *barrier,
+    struct ck_barrier_dissemination_flag **barrier_internal,
+    unsigned int nthr)
+{
+	unsigned int i, j, k, size, offset;
+	bool p = nthr & (nthr - 1);
+
+	barrier->nthr = nthr;
+	barrier->size = size = ck_internal_log(ck_internal_power_2(nthr));
+	ck_pr_store_uint(&barrier->tid, 0);
+
+	for (i = 0; i < nthr; ++i) {
+		barrier[i].flags[0] = barrier_internal[i];
+		barrier[i].flags[1] = barrier_internal[i] + size;
+	}
+
+	for (i = 0; i < nthr; ++i) {
+		for (k = 0, offset = 1; k < size; ++k, offset <<= 1) {
+			/*
+			 * Determine the thread's partner, j, for the current round, k.
+			 * Partners are chosen such that by the completion of the barrier,
+			 * every thread has been directly (having one of its flag set) or
+			 * indirectly (having one of its partners's flags set) signaled
+			 * by every other thread in the barrier.
+			 */
+			if (p == false)
+				j = (i + offset) & (nthr - 1);
+			else
+				j = (i + offset) % nthr;
+
+			/* Set the thread's partner for round k. */
+			barrier[i].flags[0][k].pflag = &barrier[j].flags[0][k].tflag;
+			barrier[i].flags[1][k].pflag = &barrier[j].flags[1][k].tflag;
+
+			/* Set the thread's flags to false. */
+			barrier[i].flags[0][k].tflag = barrier[i].flags[1][k].tflag = 0;
+		}
+	}
+
+	return;
+}
+
+void
+ck_barrier_dissemination_subscribe(struct ck_barrier_dissemination *barrier,
+    struct ck_barrier_dissemination_state *state)
+{
+
+	state->parity = 0;
+	state->sense = ~0;
+	state->tid = ck_pr_faa_uint(&barrier->tid, 1);
+	return;
+}
+
+unsigned int
+ck_barrier_dissemination_size(unsigned int nthr)
+{
+
+	return (ck_internal_log(ck_internal_power_2(nthr)) << 1);
+}
+
+void
+ck_barrier_dissemination(struct ck_barrier_dissemination *barrier,
+    struct ck_barrier_dissemination_state *state)
+{
+	unsigned int i;
+	unsigned int size = barrier->size;
+
+	for (i = 0; i < size; ++i) {
+		unsigned int *pflag, *tflag;
+
+		pflag = barrier[state->tid].flags[state->parity][i].pflag;
+		tflag = &barrier[state->tid].flags[state->parity][i].tflag;
+
+		/* Unblock current partner. */
+		ck_pr_store_uint(pflag, state->sense);
+
+		/* Wait until some other thread unblocks this one. */
+		while (ck_pr_load_uint(tflag) != state->sense)
+			ck_pr_stall();
+	}
+
+	/*
+	 * Dissemination barriers use two sets of flags to prevent race conditions
+	 * between successive calls to the barrier. Parity indicates which set will
+	 * be used for the next barrier. They also use a sense reversal technique
+	 * to avoid re-initialization of the flags for every two calls to the barrier.
+	 */
+	if (state->parity == 1)
+		state->sense = ~state->sense;
+
+	state->parity = 1 - state->parity;
+
+	ck_pr_fence_acquire();
+	return;
+}
diff --git a/src/ck_barrier_mcs.c b/src/ck_barrier_mcs.c
new file mode 100644
index 0000000..cf06017
--- /dev/null
+++ b/src/ck_barrier_mcs.c
@@ -0,0 +1,141 @@
+/*
+ * Copyright 2011-2015 Samy Al Bahra.
+ * Copyright 2011 David Joseph.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <ck_barrier.h>
+#include <ck_cc.h>
+#include <ck_pr.h>
+#include <ck_stdbool.h>
+
+void
+ck_barrier_mcs_init(struct ck_barrier_mcs *barrier, unsigned int nthr)
+{
+	unsigned int i, j;
+
+	ck_pr_store_uint(&barrier->tid, 0);
+
+	for (i = 0; i < nthr; ++i) {
+		for (j = 0; j < 4; ++j) {
+			/*
+			 * If there are still threads that don't have parents,
+			 * add it as a child.
+			 */
+			barrier[i].havechild[j] = ((i << 2) + j < nthr - 1) ? ~0 : 0;
+
+			/*
+			 * childnotready is initialized to havechild to ensure
+			 * a thread does not wait for a child that does not exist.
+			 */
+			barrier[i].childnotready[j] = barrier[i].havechild[j];
+		}
+
+		/* The root thread does not have a parent. */
+		barrier[i].parent = (i == 0) ?
+		    &barrier[i].dummy :
+		    &barrier[(i - 1) >> 2].childnotready[(i - 1) & 3];
+
+		/* Leaf threads do not have any children. */
+		barrier[i].children[0] = ((i << 1) + 1 >= nthr)	?
+		    &barrier[i].dummy :
+		    &barrier[(i << 1) + 1].parentsense;
+
+		barrier[i].children[1] = ((i << 1) + 2 >= nthr)	?
+		    &barrier[i].dummy :
+		    &barrier[(i << 1) + 2].parentsense;
+
+		barrier[i].parentsense = 0;
+	}
+
+	return;
+}
+
+void
+ck_barrier_mcs_subscribe(struct ck_barrier_mcs *barrier, struct ck_barrier_mcs_state *state)
+{
+
+	state->sense = ~0;
+	state->vpid = ck_pr_faa_uint(&barrier->tid, 1);
+	return;
+}
+
+CK_CC_INLINE static bool
+ck_barrier_mcs_check_children(unsigned int *childnotready)
+{
+
+	if (ck_pr_load_uint(&childnotready[0]) != 0)
+		return false;
+	if (ck_pr_load_uint(&childnotready[1]) != 0)
+		return false;
+	if (ck_pr_load_uint(&childnotready[2]) != 0)
+		return false;
+	if (ck_pr_load_uint(&childnotready[3]) != 0)
+		return false;
+
+	return true;
+}
+
+CK_CC_INLINE static void
+ck_barrier_mcs_reinitialize_children(struct ck_barrier_mcs *node)
+{
+
+	ck_pr_store_uint(&node->childnotready[0], node->havechild[0]);
+	ck_pr_store_uint(&node->childnotready[1], node->havechild[1]);
+	ck_pr_store_uint(&node->childnotready[2], node->havechild[2]);
+	ck_pr_store_uint(&node->childnotready[3], node->havechild[3]);
+	return;
+}
+
+void
+ck_barrier_mcs(struct ck_barrier_mcs *barrier,
+    struct ck_barrier_mcs_state *state)
+{
+
+	/*
+	 * Wait until all children have reached the barrier and are done waiting
+	 * for their children.
+	 */
+	while (ck_barrier_mcs_check_children(barrier[state->vpid].childnotready) == false)
+		ck_pr_stall();
+
+	/* Reinitialize for next barrier. */
+	ck_barrier_mcs_reinitialize_children(&barrier[state->vpid]);
+
+	/* Inform parent thread and its children have arrived at the barrier. */
+	ck_pr_store_uint(barrier[state->vpid].parent, 0);
+
+	/* Wait until parent indicates all threads have arrived at the barrier. */
+	if (state->vpid != 0) {
+		while (ck_pr_load_uint(&barrier[state->vpid].parentsense) != state->sense)
+			ck_pr_stall();
+	}
+
+	/* Inform children of successful barrier. */
+	ck_pr_store_uint(barrier[state->vpid].children[0], state->sense);
+	ck_pr_store_uint(barrier[state->vpid].children[1], state->sense);
+	state->sense = ~state->sense;
+	ck_pr_fence_memory();
+	return;
+}
diff --git a/src/ck_barrier_tournament.c b/src/ck_barrier_tournament.c
new file mode 100644
index 0000000..e232dbc
--- /dev/null
+++ b/src/ck_barrier_tournament.c
@@ -0,0 +1,184 @@
+/*
+ * Copyright 2011-2015 Samy Al Bahra.
+ * Copyright 2011 David Joseph.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <ck_barrier.h>
+#include <ck_pr.h>
+
+#include "ck_internal.h"
+
+/*
+ * This is a tournament barrier implementation. Threads are statically
+ * assigned roles to perform for each round of the barrier. Winners
+ * move on to the next round, while losers spin in their current rounds
+ * on their own flags. During the last round, the champion of the tournament
+ * sets the last flag that begins the wakeup process.
+ */
+
+enum {
+	CK_BARRIER_TOURNAMENT_BYE,
+	CK_BARRIER_TOURNAMENT_CHAMPION,
+	CK_BARRIER_TOURNAMENT_DROPOUT,
+	CK_BARRIER_TOURNAMENT_LOSER,
+	CK_BARRIER_TOURNAMENT_WINNER
+};
+
+void
+ck_barrier_tournament_subscribe(struct ck_barrier_tournament *barrier,
+    struct ck_barrier_tournament_state *state)
+{
+
+	state->sense = ~0;
+	state->vpid = ck_pr_faa_uint(&barrier->tid, 1);
+	return;
+}
+
+void
+ck_barrier_tournament_init(struct ck_barrier_tournament *barrier,
+    struct ck_barrier_tournament_round **rounds,
+    unsigned int nthr)
+{
+	unsigned int i, k, size, twok, twokm1, imod2k;
+
+	ck_pr_store_uint(&barrier->tid, 0);
+	barrier->size = size = ck_barrier_tournament_size(nthr);
+
+	for (i = 0; i < nthr; ++i) {
+		/* The first role is always CK_BARRIER_TOURNAMENT_DROPOUT. */
+		rounds[i][0].flag = 0;
+		rounds[i][0].role = CK_BARRIER_TOURNAMENT_DROPOUT;
+		for (k = 1, twok = 2, twokm1 = 1; k < size; ++k, twokm1 = twok, twok <<= 1) {
+			rounds[i][k].flag = 0;
+
+			imod2k = i & (twok - 1);
+			if (imod2k == 0) {
+				if ((i + twokm1 < nthr) && (twok < nthr))
+					rounds[i][k].role = CK_BARRIER_TOURNAMENT_WINNER;
+				else if (i + twokm1 >= nthr)
+					rounds[i][k].role = CK_BARRIER_TOURNAMENT_BYE;
+			}
+
+			if (imod2k == twokm1)
+				rounds[i][k].role = CK_BARRIER_TOURNAMENT_LOSER;
+			else if ((i == 0) && (twok >= nthr))
+				rounds[i][k].role = CK_BARRIER_TOURNAMENT_CHAMPION;
+
+			if (rounds[i][k].role == CK_BARRIER_TOURNAMENT_LOSER)
+				rounds[i][k].opponent = &rounds[i - twokm1][k].flag;
+			else if (rounds[i][k].role == CK_BARRIER_TOURNAMENT_WINNER ||
+				 rounds[i][k].role == CK_BARRIER_TOURNAMENT_CHAMPION)
+				rounds[i][k].opponent = &rounds[i + twokm1][k].flag;
+		}
+	}
+
+	ck_pr_store_ptr(&barrier->rounds, rounds);
+	return;
+}
+
+unsigned int
+ck_barrier_tournament_size(unsigned int nthr)
+{
+
+	return (ck_internal_log(ck_internal_power_2(nthr)) + 1);
+}
+
+void
+ck_barrier_tournament(struct ck_barrier_tournament *barrier,
+    struct ck_barrier_tournament_state *state)
+{
+	struct ck_barrier_tournament_round **rounds = ck_pr_load_ptr(&barrier->rounds);
+	int round = 1;
+
+	if (barrier->size == 1)
+		return;
+
+	for (;; ++round) {
+		switch (rounds[state->vpid][round].role) {
+		case CK_BARRIER_TOURNAMENT_BYE:
+			break;
+		case CK_BARRIER_TOURNAMENT_CHAMPION:
+			/*
+			 * The CK_BARRIER_TOURNAMENT_CHAMPION waits until it wins the tournament; it then
+			 * sets the final flag before the wakeup phase of the barrier.
+			 */
+			while (ck_pr_load_uint(&rounds[state->vpid][round].flag) != state->sense)
+				ck_pr_stall();
+
+			ck_pr_store_uint(rounds[state->vpid][round].opponent, state->sense);
+			goto wakeup;
+		case CK_BARRIER_TOURNAMENT_DROPOUT:
+			/* NOTREACHED */
+			break;
+		case CK_BARRIER_TOURNAMENT_LOSER:
+			/*
+			 * CK_BARRIER_TOURNAMENT_LOSERs set the flags of their opponents and wait until
+			 * their opponents release them after the tournament is over.
+			 */
+			ck_pr_store_uint(rounds[state->vpid][round].opponent, state->sense);
+			while (ck_pr_load_uint(&rounds[state->vpid][round].flag) != state->sense)
+				ck_pr_stall();
+
+			goto wakeup;
+		case CK_BARRIER_TOURNAMENT_WINNER:
+			/*
+			 * CK_BARRIER_TOURNAMENT_WINNERs wait until their current opponent sets their flag; they then
+			 * continue to the next round of the tournament.
+			 */
+			while (ck_pr_load_uint(&rounds[state->vpid][round].flag) != state->sense)
+				ck_pr_stall();
+			break;
+		}
+	}
+
+wakeup:
+	for (round -= 1 ;; --round) {
+		switch (rounds[state->vpid][round].role) {
+		case CK_BARRIER_TOURNAMENT_BYE:
+			break;
+		case CK_BARRIER_TOURNAMENT_CHAMPION:
+			/* NOTREACHED */
+			break;
+		case CK_BARRIER_TOURNAMENT_DROPOUT:
+			goto leave;
+			break;
+		case CK_BARRIER_TOURNAMENT_LOSER:
+			/* NOTREACHED */
+			break;
+		case CK_BARRIER_TOURNAMENT_WINNER:
+			/*
+			 * Winners inform their old opponents the tournament is over
+			 * by setting their flags.
+			 */
+			ck_pr_store_uint(rounds[state->vpid][round].opponent, state->sense);
+			break;
+		}
+	}
+
+leave:
+	ck_pr_fence_memory();
+	state->sense = ~state->sense;
+	return;
+}
diff --git a/src/ck_epoch.c b/src/ck_epoch.c
new file mode 100644
index 0000000..a0e9180
--- /dev/null
+++ b/src/ck_epoch.c
@@ -0,0 +1,545 @@
+/*
+ * Copyright 2011-2015 Samy Al Bahra.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * The implementation here is inspired from the work described in:
+ *   Fraser, K. 2004. Practical Lock-Freedom. PhD Thesis, University
+ *   of Cambridge Computing Laboratory.
+ */
+
+#include <ck_backoff.h>
+#include <ck_cc.h>
+#include <ck_epoch.h>
+#include <ck_pr.h>
+#include <ck_stack.h>
+#include <ck_stdbool.h>
+#include <ck_string.h>
+
+/*
+ * Only three distinct values are used for reclamation, but reclamation occurs
+ * at e+2 rather than e+1. Any thread in a "critical section" would have
+ * acquired some snapshot (e) of the global epoch value (e_g) and set an active
+ * flag. Any hazardous references will only occur after a full memory barrier.
+ * For example, assume an initial e_g value of 1, e value of 0 and active value
+ * of 0.
+ *
+ * ck_epoch_begin(...)
+ *   e = e_g
+ *   active = 1
+ *   memory_barrier();
+ *
+ * Any serialized reads may observe e = 0 or e = 1 with active = 0, or e = 0 or
+ * e = 1 with active = 1. The e_g value can only go from 1 to 2 if every thread
+ * has already observed the value of "1" (or the value we are incrementing
+ * from). This guarantees us that for any given value e_g, any threads with-in
+ * critical sections (referred to as "active" threads from here on) would have
+ * an e value of e_g-1 or e_g. This also means that hazardous references may be
+ * shared in both e_g-1 and e_g even if they are logically deleted in e_g.
+ *
+ * For example, assume all threads have an e value of e_g. Another thread may
+ * increment to e_g to e_g+1. Older threads may have a reference to an object
+ * which is only deleted in e_g+1. It could be that reader threads are
+ * executing some hash table look-ups, while some other writer thread (which
+ * causes epoch counter tick) actually deletes the same items that reader
+ * threads are looking up (this writer thread having an e value of e_g+1).
+ * This is possible if the writer thread re-observes the epoch after the
+ * counter tick.
+ *
+ * Psuedo-code for writer:
+ *   ck_epoch_begin()
+ *   ht_delete(x)
+ *   ck_epoch_end()
+ *   ck_epoch_begin()
+ *   ht_delete(x)
+ *   ck_epoch_end()
+ *
+ * Psuedo-code for reader:
+ *   for (;;) {
+ *      x = ht_lookup(x)
+ *      ck_pr_inc(&x->value);
+ *   }
+ *
+ * Of course, it is also possible for references logically deleted at e_g-1 to
+ * still be accessed at e_g as threads are "active" at the same time
+ * (real-world time) mutating shared objects.
+ *
+ * Now, if the epoch counter is ticked to e_g+1, then no new hazardous
+ * references could exist to objects logically deleted at e_g-1. The reason for
+ * this is that at e_g+1, all epoch read-side critical sections started at
+ * e_g-1 must have been completed. If any epoch read-side critical sections at
+ * e_g-1 were still active, then we would never increment to e_g+1 (active != 0
+ * ^ e != e_g).  Additionally, e_g may still have hazardous references to
+ * objects logically deleted at e_g-1 which means objects logically deleted at
+ * e_g-1 cannot be deleted at e_g+1 unless all threads have observed e_g+1
+ * (since it is valid for active threads to be at e_g and threads at e_g still
+ * require safe memory accesses).
+ *
+ * However, at e_g+2, all active threads must be either at e_g+1 or e_g+2.
+ * Though e_g+2 may share hazardous references with e_g+1, and e_g+1 shares
+ * hazardous references to e_g, no active threads are at e_g or e_g-1. This
+ * means no hazardous references could exist to objects deleted at e_g-1 (at
+ * e_g+2).
+ *
+ * To summarize these important points,
+ *   1) Active threads will always have a value of e_g or e_g-1.
+ *   2) Items that are logically deleted e_g or e_g-1 cannot be physically
+ *      deleted.
+ *   3) Objects logically deleted at e_g-1 can be physically destroyed at e_g+2
+ *      or at e_g+1 if no threads are at e_g.
+ *
+ * Last but not least, if we are at e_g+2, then no active thread is at e_g
+ * which means it is safe to apply modulo-3 arithmetic to e_g value in order to
+ * re-use e_g to represent the e_g+3 state. This means it is sufficient to
+ * represent e_g using only the values 0, 1 or 2. Every time a thread re-visits
+ * a e_g (which can be determined with a non-empty deferral list) it can assume
+ * objects in the e_g deferral list involved at least three e_g transitions and
+ * are thus, safe, for physical deletion.
+ *
+ * Blocking semantics for epoch reclamation have additional restrictions.
+ * Though we only require three deferral lists, reasonable blocking semantics
+ * must be able to more gracefully handle bursty write work-loads which could
+ * easily cause e_g wrap-around if modulo-3 arithmetic is used. This allows for
+ * easy-to-trigger live-lock situations. The work-around to this is to not
+ * apply modulo arithmetic to e_g but only to deferral list indexing.
+ */
+#define CK_EPOCH_GRACE 3U
+
+enum {
+	CK_EPOCH_STATE_USED = 0,
+	CK_EPOCH_STATE_FREE = 1
+};
+
+CK_STACK_CONTAINER(struct ck_epoch_record, record_next,
+    ck_epoch_record_container)
+CK_STACK_CONTAINER(struct ck_epoch_entry, stack_entry,
+    ck_epoch_entry_container)
+
+#define CK_EPOCH_SENSE_MASK	(CK_EPOCH_SENSE - 1)
+
+void
+_ck_epoch_delref(struct ck_epoch_record *record,
+    struct ck_epoch_section *section)
+{
+	struct ck_epoch_ref *current, *other;
+	unsigned int i = section->bucket;
+
+	current = &record->local.bucket[i];
+	current->count--;
+
+	if (current->count > 0)
+		return;
+
+	/*
+	 * If the current bucket no longer has any references, then
+	 * determine whether we have already transitioned into a newer
+	 * epoch. If so, then make sure to update our shared snapshot
+	 * to allow for forward progress.
+	 *
+	 * If no other active bucket exists, then the record will go
+	 * inactive in order to allow for forward progress.
+	 */
+	other = &record->local.bucket[(i + 1) &
+	    CK_EPOCH_SENSE_MASK];
+	if (other->count > 0 &&
+	    ((int)(current->epoch - other->epoch) < 0)) {
+		/*
+		 * The other epoch value is actually the newest,
+		 * transition to it.
+		 */
+		ck_pr_store_uint(&record->epoch, other->epoch);
+	}
+
+	return;
+}
+
+void
+_ck_epoch_addref(struct ck_epoch_record *record,
+    struct ck_epoch_section *section)
+{
+	struct ck_epoch *global = record->global;
+	struct ck_epoch_ref *ref;
+	unsigned int epoch, i;
+
+	epoch = ck_pr_load_uint(&global->epoch);
+	i = epoch & CK_EPOCH_SENSE_MASK;
+	ref = &record->local.bucket[i];
+
+	if (ref->count++ == 0) {
+#ifndef CK_MD_TSO
+		struct ck_epoch_ref *previous;
+
+		/*
+		 * The system has already ticked. If another non-zero bucket
+		 * exists, make sure to order our observations with respect
+		 * to it. Otherwise, it is possible to acquire a reference
+		 * from the previous epoch generation.
+		 *
+		 * On TSO architectures, the monoticity of the global counter
+		 * and load-{store, load} ordering are sufficient to guarantee
+		 * this ordering.
+		 */
+		previous = &record->local.bucket[(i + 1) &
+		    CK_EPOCH_SENSE_MASK];
+		if (previous->count > 0)
+			ck_pr_fence_acqrel();
+#endif /* !CK_MD_TSO */
+
+		/*
+		 * If this is this is a new reference into the current
+		 * bucket then cache the associated epoch value.
+		 */
+		ref->epoch = epoch;
+	}
+
+	section->bucket = i;
+	return;
+}
+
+void
+ck_epoch_init(struct ck_epoch *global)
+{
+
+	ck_stack_init(&global->records);
+	global->epoch = 1;
+	global->n_free = 0;
+	ck_pr_fence_store();
+	return;
+}
+
+struct ck_epoch_record *
+ck_epoch_recycle(struct ck_epoch *global)
+{
+	struct ck_epoch_record *record;
+	ck_stack_entry_t *cursor;
+	unsigned int state;
+
+	if (ck_pr_load_uint(&global->n_free) == 0)
+		return NULL;
+
+	CK_STACK_FOREACH(&global->records, cursor) {
+		record = ck_epoch_record_container(cursor);
+
+		if (ck_pr_load_uint(&record->state) == CK_EPOCH_STATE_FREE) {
+			/* Serialize with respect to deferral list clean-up. */
+			ck_pr_fence_load();
+			state = ck_pr_fas_uint(&record->state,
+			    CK_EPOCH_STATE_USED);
+			if (state == CK_EPOCH_STATE_FREE) {
+				ck_pr_dec_uint(&global->n_free);
+				return record;
+			}
+		}
+	}
+
+	return NULL;
+}
+
+void
+ck_epoch_register(struct ck_epoch *global, struct ck_epoch_record *record)
+{
+	size_t i;
+
+	record->global = global;
+	record->state = CK_EPOCH_STATE_USED;
+	record->active = 0;
+	record->epoch = 0;
+	record->n_dispatch = 0;
+	record->n_peak = 0;
+	record->n_pending = 0;
+	memset(&record->local, 0, sizeof record->local);
+
+	for (i = 0; i < CK_EPOCH_LENGTH; i++)
+		ck_stack_init(&record->pending[i]);
+
+	ck_pr_fence_store();
+	ck_stack_push_upmc(&global->records, &record->record_next);
+	return;
+}
+
+void
+ck_epoch_unregister(struct ck_epoch_record *record)
+{
+	struct ck_epoch *global = record->global;
+	size_t i;
+
+	record->active = 0;
+	record->epoch = 0;
+	record->n_dispatch = 0;
+	record->n_peak = 0;
+	record->n_pending = 0;
+	memset(&record->local, 0, sizeof record->local);
+
+	for (i = 0; i < CK_EPOCH_LENGTH; i++)
+		ck_stack_init(&record->pending[i]);
+
+	ck_pr_fence_store();
+	ck_pr_store_uint(&record->state, CK_EPOCH_STATE_FREE);
+	ck_pr_inc_uint(&global->n_free);
+	return;
+}
+
+static struct ck_epoch_record *
+ck_epoch_scan(struct ck_epoch *global,
+    struct ck_epoch_record *cr,
+    unsigned int epoch,
+    bool *af)
+{
+	ck_stack_entry_t *cursor;
+
+	if (cr == NULL) {
+		cursor = CK_STACK_FIRST(&global->records);
+		*af = false;
+	} else {
+		cursor = &cr->record_next;
+		*af = true;
+	}
+
+	while (cursor != NULL) {
+		unsigned int state, active;
+
+		cr = ck_epoch_record_container(cursor);
+
+		state = ck_pr_load_uint(&cr->state);
+		if (state & CK_EPOCH_STATE_FREE) {
+			cursor = CK_STACK_NEXT(cursor);
+			continue;
+		}
+
+		active = ck_pr_load_uint(&cr->active);
+		*af |= active;
+
+		if (active != 0 && ck_pr_load_uint(&cr->epoch) != epoch)
+			return cr;
+
+		cursor = CK_STACK_NEXT(cursor);
+	}
+
+	return NULL;
+}
+
+static void
+ck_epoch_dispatch(struct ck_epoch_record *record, unsigned int e)
+{
+	unsigned int epoch = e & (CK_EPOCH_LENGTH - 1);
+	ck_stack_entry_t *head, *next, *cursor;
+	unsigned int i = 0;
+
+	head = CK_STACK_FIRST(&record->pending[epoch]);
+	ck_stack_init(&record->pending[epoch]);
+
+	for (cursor = head; cursor != NULL; cursor = next) {
+		struct ck_epoch_entry *entry =
+		    ck_epoch_entry_container(cursor);
+
+		next = CK_STACK_NEXT(cursor);
+		entry->function(entry);
+		i++;
+	}
+
+	if (record->n_pending > record->n_peak)
+		record->n_peak = record->n_pending;
+
+	record->n_dispatch += i;
+	record->n_pending -= i;
+	return;
+}
+
+/*
+ * Reclaim all objects associated with a record.
+ */
+void
+ck_epoch_reclaim(struct ck_epoch_record *record)
+{
+	unsigned int epoch;
+
+	for (epoch = 0; epoch < CK_EPOCH_LENGTH; epoch++)
+		ck_epoch_dispatch(record, epoch);
+
+	return;
+}
+
+/*
+ * This function must not be called with-in read section.
+ */
+void
+ck_epoch_synchronize(struct ck_epoch_record *record)
+{
+	struct ck_epoch *global = record->global;
+	struct ck_epoch_record *cr;
+	unsigned int delta, epoch, goal, i;
+	bool active;
+
+	ck_pr_fence_memory();
+
+	/*
+	 * The observation of the global epoch must be ordered with respect to
+	 * all prior operations. The re-ordering of loads is permitted given
+	 * monoticity of global epoch counter.
+	 *
+	 * If UINT_MAX concurrent mutations were to occur then it is possible
+	 * to encounter an ABA-issue. If this is a concern, consider tuning
+	 * write-side concurrency.
+	 */
+	delta = epoch = ck_pr_load_uint(&global->epoch);
+	goal = epoch + CK_EPOCH_GRACE;
+
+	for (i = 0, cr = NULL; i < CK_EPOCH_GRACE - 1; cr = NULL, i++) {
+		bool r;
+
+		/*
+		 * Determine whether all threads have observed the current
+		 * epoch with respect to the updates on invocation.
+		 */
+		while (cr = ck_epoch_scan(global, cr, delta, &active),
+		    cr != NULL) {
+			unsigned int e_d;
+
+			ck_pr_stall();
+
+			/*
+			 * Another writer may have already observed a grace
+			 * period.
+			 */
+			e_d = ck_pr_load_uint(&global->epoch);
+			if (e_d != delta) {
+				delta = e_d;
+				goto reload;
+			}
+		}
+
+		/*
+		 * If we have observed all threads as inactive, then we assume
+		 * we are at a grace period.
+		 */
+		if (active == false)
+			break;
+
+		/*
+		 * Increment current epoch. CAS semantics are used to eliminate
+		 * increment operations for synchronization that occurs for the
+		 * same global epoch value snapshot.
+		 *
+		 * If we can guarantee there will only be one active barrier or
+		 * epoch tick at a given time, then it is sufficient to use an
+		 * increment operation. In a multi-barrier workload, however,
+		 * it is possible to overflow the epoch value if we apply
+		 * modulo-3 arithmetic.
+		 */
+		r = ck_pr_cas_uint_value(&global->epoch, delta, delta + 1,
+		    &delta);
+
+		/* Order subsequent thread active checks. */
+		ck_pr_fence_atomic_load();
+
+		/*
+		 * If CAS has succeeded, then set delta to latest snapshot.
+		 * Otherwise, we have just acquired latest snapshot.
+		 */
+		delta = delta + r;
+		continue;
+
+reload:
+		if ((goal > epoch) & (delta >= goal)) {
+			/*
+			 * Right now, epoch overflow is handled as an edge
+			 * case. If we have already observed an epoch
+			 * generation, then we can be sure no hazardous
+			 * references exist to objects from this generation. We
+			 * can actually avoid an addtional scan step at this
+			 * point.
+			 */
+			break;
+		}
+	}
+
+	/*
+	 * A majority of use-cases will not require full barrier semantics.
+	 * However, if non-temporal instructions are used, full barrier
+	 * semantics are necessary.
+	 */
+	ck_pr_fence_memory();
+	record->epoch = delta;
+	return;
+}
+
+void
+ck_epoch_barrier(struct ck_epoch_record *record)
+{
+
+	ck_epoch_synchronize(record);
+	ck_epoch_reclaim(record);
+	return;
+}
+
+/*
+ * It may be worth it to actually apply these deferral semantics to an epoch
+ * that was observed at ck_epoch_call time. The problem is that the latter
+ * would require a full fence.
+ *
+ * ck_epoch_call will dispatch to the latest epoch snapshot that was observed.
+ * There are cases where it will fail to reclaim as early as it could. If this
+ * becomes a problem, we could actually use a heap for epoch buckets but that
+ * is far from ideal too.
+ */
+bool
+ck_epoch_poll(struct ck_epoch_record *record)
+{
+	bool active;
+	unsigned int epoch;
+	unsigned int snapshot;
+	struct ck_epoch_record *cr = NULL;
+	struct ck_epoch *global = record->global;
+
+	epoch = ck_pr_load_uint(&global->epoch);
+
+	/* Serialize epoch snapshots with respect to global epoch. */
+	ck_pr_fence_memory();
+	cr = ck_epoch_scan(global, cr, epoch, &active);
+	if (cr != NULL) {
+		record->epoch = epoch;
+		return false;
+	}
+
+	/* We are at a grace period if all threads are inactive. */
+	if (active == false) {
+		record->epoch = epoch;
+		for (epoch = 0; epoch < CK_EPOCH_LENGTH; epoch++)
+			ck_epoch_dispatch(record, epoch);
+
+		return true;
+	}
+
+	/* If an active thread exists, rely on epoch observation. */
+	if (ck_pr_cas_uint_value(&global->epoch, epoch, epoch + 1,
+	    &snapshot) == false) {
+		record->epoch = snapshot;
+	} else {
+		record->epoch = epoch + 1;
+	}
+
+	ck_epoch_dispatch(record, epoch + 1);
+	return true;
+}
diff --git a/src/ck_hp.c b/src/ck_hp.c
new file mode 100644
index 0000000..32df92e
--- /dev/null
+++ b/src/ck_hp.c
@@ -0,0 +1,323 @@
+/*
+ * Copyright 2010-2015 Samy Al Bahra.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * (c) Copyright 2008, IBM Corporation.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * This is an implementation of hazard pointers as detailed in:
+ *   http://www.research.ibm.com/people/m/michael/ieeetpds-2004.pdf
+ *
+ * This API provides a publishing mechanism that defers destruction of
+ * hazard pointers until it is safe to do so. Preventing arbitrary re-use
+ * protects against the ABA problem and provides safe memory reclamation.
+ * The implementation was derived from the Hazard Pointers implementation
+ * from the Amino CBBS project. It has been heavily modified for Concurrency
+ * Kit.
+ */
+
+#include <ck_backoff.h>
+#include <ck_cc.h>
+#include <ck_hp.h>
+#include <ck_pr.h>
+#include <ck_stack.h>
+#include <ck_stdbool.h>
+#include <ck_stddef.h>
+#include <ck_stdlib.h>
+#include <ck_string.h>
+
+CK_STACK_CONTAINER(struct ck_hp_record, global_entry, ck_hp_record_container)
+CK_STACK_CONTAINER(struct ck_hp_hazard, pending_entry, ck_hp_hazard_container)
+
+void
+ck_hp_init(struct ck_hp *state,
+	   unsigned int degree,
+	   unsigned int threshold,
+	   ck_hp_destructor_t destroy)
+{
+
+	state->threshold = threshold;
+	state->degree = degree;
+	state->destroy = destroy;
+	state->n_subscribers = 0;
+	state->n_free = 0;
+	ck_stack_init(&state->subscribers);
+	ck_pr_fence_store();
+
+	return;
+}
+
+void
+ck_hp_set_threshold(struct ck_hp *state, unsigned int threshold)
+{
+
+	ck_pr_store_uint(&state->threshold, threshold);
+	return;
+}
+
+struct ck_hp_record *
+ck_hp_recycle(struct ck_hp *global)
+{
+	struct ck_hp_record *record;
+	ck_stack_entry_t *entry;
+	int state;
+
+	if (ck_pr_load_uint(&global->n_free) == 0)
+		return NULL;
+
+	CK_STACK_FOREACH(&global->subscribers, entry) {
+		record = ck_hp_record_container(entry);
+
+		if (ck_pr_load_int(&record->state) == CK_HP_FREE) {
+			ck_pr_fence_load();
+			state = ck_pr_fas_int(&record->state, CK_HP_USED);
+			if (state == CK_HP_FREE) {
+				ck_pr_dec_uint(&global->n_free);
+				return record;
+			}
+		}
+	}
+
+	return NULL;
+}
+
+void
+ck_hp_unregister(struct ck_hp_record *entry)
+{
+
+	entry->n_pending = 0;
+	entry->n_peak = 0;
+	entry->n_reclamations = 0;
+	ck_stack_init(&entry->pending);
+	ck_pr_fence_store();
+	ck_pr_store_int(&entry->state, CK_HP_FREE);
+	ck_pr_inc_uint(&entry->global->n_free);
+	return;
+}
+
+void
+ck_hp_register(struct ck_hp *state,
+    struct ck_hp_record *entry,
+    void **pointers)
+{
+
+	entry->state = CK_HP_USED;
+	entry->global = state;
+	entry->pointers = pointers;
+	entry->n_pending = 0;
+	entry->n_peak = 0;
+	entry->n_reclamations = 0;
+	memset(pointers, 0, state->degree * sizeof(void *));
+	ck_stack_init(&entry->pending);
+	ck_pr_fence_store();
+	ck_stack_push_upmc(&state->subscribers, &entry->global_entry);
+	ck_pr_inc_uint(&state->n_subscribers);
+	return;
+}
+
+static int
+hazard_compare(const void *a, const void *b)
+{
+	void * const *x;
+	void * const *y;
+
+	x = a;
+	y = b;
+	return ((*x > *y) - (*x < *y));
+}
+
+CK_CC_INLINE static bool
+ck_hp_member_scan(ck_stack_entry_t *entry, unsigned int degree, void *pointer)
+{
+	struct ck_hp_record *record;
+	unsigned int i;
+	void *hazard;
+
+	do {
+		record = ck_hp_record_container(entry);
+		if (ck_pr_load_int(&record->state) == CK_HP_FREE)
+			continue;
+
+		if (ck_pr_load_ptr(&record->pointers) == NULL)
+			continue;
+
+		for (i = 0; i < degree; i++) {
+			hazard = ck_pr_load_ptr(&record->pointers[i]);
+			if (hazard == pointer)
+				return (true);
+		}
+	} while ((entry = CK_STACK_NEXT(entry)) != NULL);
+
+	return (false);
+}
+
+CK_CC_INLINE static void *
+ck_hp_member_cache(struct ck_hp *global, void **cache, unsigned int *n_hazards)
+{
+	struct ck_hp_record *record;
+	ck_stack_entry_t *entry;
+	unsigned int hazards = 0;
+	unsigned int i;
+	void *pointer;
+
+	CK_STACK_FOREACH(&global->subscribers, entry) {
+		record = ck_hp_record_container(entry);
+		if (ck_pr_load_int(&record->state) == CK_HP_FREE)
+			continue;
+
+		if (ck_pr_load_ptr(&record->pointers) == NULL)
+			continue;
+
+		for (i = 0; i < global->degree; i++) {
+			if (hazards > CK_HP_CACHE)
+				break;
+
+			pointer = ck_pr_load_ptr(&record->pointers[i]);
+			if (pointer != NULL)
+				cache[hazards++] = pointer;
+		}
+	}
+
+	*n_hazards = hazards;
+	return (entry);
+}
+
+void
+ck_hp_reclaim(struct ck_hp_record *thread)
+{
+	struct ck_hp_hazard *hazard;
+	struct ck_hp *global = thread->global;
+	unsigned int n_hazards;
+	void **cache, *marker, *match;
+	ck_stack_entry_t *previous, *entry, *next;
+
+	/* Store as many entries as possible in local array. */
+	cache = thread->cache;
+	marker = ck_hp_member_cache(global, cache, &n_hazards);
+
+	/*
+	 * In theory, there is an n such that (n * (log n) ** 2) < np.
+	 */
+	qsort(cache, n_hazards, sizeof(void *), hazard_compare);
+
+	previous = NULL;
+	CK_STACK_FOREACH_SAFE(&thread->pending, entry, next) {
+		hazard = ck_hp_hazard_container(entry);
+		match = bsearch(&hazard->pointer, cache, n_hazards,
+				  sizeof(void *), hazard_compare);
+		if (match != NULL) {
+			previous = entry;
+			continue;
+		}
+
+		if (marker != NULL &&
+		    ck_hp_member_scan(marker, global->degree, hazard->pointer)) {
+			previous = entry;
+			continue;
+		}
+
+		thread->n_pending -= 1;
+
+		/* Remove from the pending stack. */
+		if (previous)
+			CK_STACK_NEXT(previous) = CK_STACK_NEXT(entry);
+		else
+			CK_STACK_FIRST(&thread->pending) = CK_STACK_NEXT(entry);
+
+		/* The entry is now safe to destroy. */
+		global->destroy(hazard->data);
+		thread->n_reclamations++;
+	}
+
+	return;
+}
+
+void
+ck_hp_retire(struct ck_hp_record *thread,
+    struct ck_hp_hazard *hazard,
+    void *data,
+    void *pointer)
+{
+
+	ck_pr_store_ptr(&hazard->pointer, pointer);
+	ck_pr_store_ptr(&hazard->data, data);
+	ck_stack_push_spnc(&thread->pending, &hazard->pending_entry);
+
+	thread->n_pending += 1;
+	if (thread->n_pending > thread->n_peak)
+		thread->n_peak = thread->n_pending;
+
+	return;
+}
+
+void
+ck_hp_free(struct ck_hp_record *thread,
+    struct ck_hp_hazard *hazard,
+    void *data,
+    void *pointer)
+{
+	struct ck_hp *global;
+
+	global = ck_pr_load_ptr(&thread->global);
+	ck_pr_store_ptr(&hazard->data, data);
+	ck_pr_store_ptr(&hazard->pointer, pointer);
+	ck_stack_push_spnc(&thread->pending, &hazard->pending_entry);
+
+	thread->n_pending += 1;
+	if (thread->n_pending > thread->n_peak)
+		thread->n_peak = thread->n_pending;
+
+	if (thread->n_pending >= global->threshold)
+		ck_hp_reclaim(thread);
+
+	return;
+}
+
+void
+ck_hp_purge(struct ck_hp_record *thread)
+{
+	ck_backoff_t backoff = CK_BACKOFF_INITIALIZER;
+
+	while (thread->n_pending > 0) {
+		ck_hp_reclaim(thread);
+		if (thread->n_pending > 0)
+			ck_backoff_eb(&backoff);
+	}
+
+	return;
+}
diff --git a/src/ck_hs.c b/src/ck_hs.c
new file mode 100644
index 0000000..31510ec
--- /dev/null
+++ b/src/ck_hs.c
@@ -0,0 +1,941 @@
+/*
+ * Copyright 2012-2015 Samy Al Bahra.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <ck_cc.h>
+#include <ck_hs.h>
+#include <ck_limits.h>
+#include <ck_md.h>
+#include <ck_pr.h>
+#include <ck_stdint.h>
+#include <ck_stdbool.h>
+#include <ck_string.h>
+
+#include "ck_internal.h"
+
+#ifndef CK_HS_PROBE_L1_SHIFT
+#define CK_HS_PROBE_L1_SHIFT 3ULL
+#endif /* CK_HS_PROBE_L1_SHIFT */
+
+#define CK_HS_PROBE_L1 (1 << CK_HS_PROBE_L1_SHIFT)
+#define CK_HS_PROBE_L1_MASK (CK_HS_PROBE_L1 - 1)
+
+#ifndef CK_HS_PROBE_L1_DEFAULT
+#define CK_HS_PROBE_L1_DEFAULT CK_MD_CACHELINE
+#endif
+
+#define CK_HS_VMA_MASK ((uintptr_t)((1ULL << CK_MD_VMA_BITS) - 1))
+#define CK_HS_VMA(x)	\
+	((void *)((uintptr_t)(x) & CK_HS_VMA_MASK))
+
+#define CK_HS_EMPTY     NULL
+#define CK_HS_TOMBSTONE ((void *)~(uintptr_t)0)
+#define CK_HS_G		(2)
+#define CK_HS_G_MASK	(CK_HS_G - 1)
+
+#if defined(CK_F_PR_LOAD_8) && defined(CK_F_PR_STORE_8)
+#define CK_HS_WORD          uint8_t
+#define CK_HS_WORD_MAX	    UINT8_MAX
+#define CK_HS_STORE(x, y)   ck_pr_store_8(x, y)
+#define CK_HS_LOAD(x)       ck_pr_load_8(x)
+#elif defined(CK_F_PR_LOAD_16) && defined(CK_F_PR_STORE_16)
+#define CK_HS_WORD          uint16_t
+#define CK_HS_WORD_MAX	    UINT16_MAX
+#define CK_HS_STORE(x, y)   ck_pr_store_16(x, y)
+#define CK_HS_LOAD(x)       ck_pr_load_16(x)
+#elif defined(CK_F_PR_LOAD_32) && defined(CK_F_PR_STORE_32)
+#define CK_HS_WORD          uint32_t
+#define CK_HS_WORD_MAX	    UINT32_MAX
+#define CK_HS_STORE(x, y)   ck_pr_store_32(x, y)
+#define CK_HS_LOAD(x)       ck_pr_load_32(x)
+#else
+#error "ck_hs is not supported on your platform."
+#endif
+
+enum ck_hs_probe_behavior {
+	CK_HS_PROBE = 0,	/* Default behavior. */
+	CK_HS_PROBE_TOMBSTONE,	/* Short-circuit on tombstone. */
+	CK_HS_PROBE_INSERT	/* Short-circuit on probe bound if tombstone found. */
+};
+
+struct ck_hs_map {
+	unsigned int generation[CK_HS_G];
+	unsigned int probe_maximum;
+	unsigned long mask;
+	unsigned long step;
+	unsigned int probe_limit;
+	unsigned int tombstones;
+	unsigned long n_entries;
+	unsigned long capacity;
+	unsigned long size;
+	CK_HS_WORD *probe_bound;
+	const void **entries;
+};
+
+static inline void
+ck_hs_map_signal(struct ck_hs_map *map, unsigned long h)
+{
+
+	h &= CK_HS_G_MASK;
+	ck_pr_store_uint(&map->generation[h],
+	    map->generation[h] + 1);
+	ck_pr_fence_store();
+	return;
+}
+
+void
+ck_hs_iterator_init(struct ck_hs_iterator *iterator)
+{
+
+	iterator->cursor = NULL;
+	iterator->offset = 0;
+	return;
+}
+
+bool
+ck_hs_next(struct ck_hs *hs, struct ck_hs_iterator *i, void **key)
+{
+	struct ck_hs_map *map = hs->map;
+	void *value;
+
+	if (i->offset >= map->capacity)
+		return false;
+
+	do {
+		value = CK_CC_DECONST_PTR(map->entries[i->offset]);
+		if (value != CK_HS_EMPTY && value != CK_HS_TOMBSTONE) {
+#ifdef CK_HS_PP
+			if (hs->mode & CK_HS_MODE_OBJECT)
+				value = CK_HS_VMA(value);
+#endif
+			i->offset++;
+			*key = value;
+			return true;
+		}
+	} while (++i->offset < map->capacity);
+
+	return false;
+}
+
+void
+ck_hs_stat(struct ck_hs *hs, struct ck_hs_stat *st)
+{
+	struct ck_hs_map *map = hs->map;
+
+	st->n_entries = map->n_entries;
+	st->tombstones = map->tombstones;
+	st->probe_maximum = map->probe_maximum;
+	return;
+}
+
+unsigned long
+ck_hs_count(struct ck_hs *hs)
+{
+
+	return hs->map->n_entries;
+}
+
+static void
+ck_hs_map_destroy(struct ck_malloc *m, struct ck_hs_map *map, bool defer)
+{
+
+	m->free(map, map->size, defer);
+	return;
+}
+
+void
+ck_hs_destroy(struct ck_hs *hs)
+{
+
+	ck_hs_map_destroy(hs->m, hs->map, false);
+	return;
+}
+
+static struct ck_hs_map *
+ck_hs_map_create(struct ck_hs *hs, unsigned long entries)
+{
+	struct ck_hs_map *map;
+	unsigned long size, n_entries, prefix, limit;
+
+	n_entries = ck_internal_power_2(entries);
+	if (n_entries < CK_HS_PROBE_L1)
+		n_entries = CK_HS_PROBE_L1;
+
+	size = sizeof(struct ck_hs_map) + (sizeof(void *) * n_entries + CK_MD_CACHELINE - 1);
+
+	if (hs->mode & CK_HS_MODE_DELETE) {
+		prefix = sizeof(CK_HS_WORD) * n_entries;
+		size += prefix;
+	} else {
+		prefix = 0;
+	}
+
+	map = hs->m->malloc(size);
+	if (map == NULL)
+		return NULL;
+
+	map->size = size;
+
+	/* We should probably use a more intelligent heuristic for default probe length. */
+	limit = ck_internal_max(n_entries >> (CK_HS_PROBE_L1_SHIFT + 2), CK_HS_PROBE_L1_DEFAULT);
+	if (limit > UINT_MAX)
+		limit = UINT_MAX;
+
+	map->probe_limit = (unsigned int)limit;
+	map->probe_maximum = 0;
+	map->capacity = n_entries;
+	map->step = ck_internal_bsf(n_entries);
+	map->mask = n_entries - 1;
+	map->n_entries = 0;
+
+	/* Align map allocation to cache line. */
+	map->entries = (void *)(((uintptr_t)&map[1] + prefix +
+	    CK_MD_CACHELINE - 1) & ~(CK_MD_CACHELINE - 1));
+
+	memset(map->entries, 0, sizeof(void *) * n_entries);
+	memset(map->generation, 0, sizeof map->generation);
+
+	if (hs->mode & CK_HS_MODE_DELETE) {
+		map->probe_bound = (CK_HS_WORD *)&map[1];
+		memset(map->probe_bound, 0, prefix);
+	} else {
+		map->probe_bound = NULL;
+	}
+
+	/* Commit entries purge with respect to map publication. */
+	ck_pr_fence_store();
+	return map;
+}
+
+bool
+ck_hs_reset_size(struct ck_hs *hs, unsigned long capacity)
+{
+	struct ck_hs_map *map, *previous;
+
+	previous = hs->map;
+	map = ck_hs_map_create(hs, capacity);
+	if (map == NULL)
+		return false;
+
+	ck_pr_store_ptr(&hs->map, map);
+	ck_hs_map_destroy(hs->m, previous, true);
+	return true;
+}
+
+bool
+ck_hs_reset(struct ck_hs *hs)
+{
+	struct ck_hs_map *previous;
+
+	previous = hs->map;
+	return ck_hs_reset_size(hs, previous->capacity);
+}
+
+static inline unsigned long
+ck_hs_map_probe_next(struct ck_hs_map *map,
+    unsigned long offset,
+    unsigned long h,
+    unsigned long level,
+    unsigned long probes)
+{
+	unsigned long r, stride;
+
+	r = (h >> map->step) >> level;
+	stride = (r & ~CK_HS_PROBE_L1_MASK) << 1 | (r & CK_HS_PROBE_L1_MASK);
+
+	return (offset + (probes >> CK_HS_PROBE_L1_SHIFT) +
+	    (stride | CK_HS_PROBE_L1)) & map->mask;
+}
+
+static inline void
+ck_hs_map_bound_set(struct ck_hs_map *m,
+    unsigned long h,
+    unsigned long n_probes)
+{
+	unsigned long offset = h & m->mask;
+
+	if (n_probes > m->probe_maximum)
+		ck_pr_store_uint(&m->probe_maximum, n_probes);
+
+	if (m->probe_bound != NULL && m->probe_bound[offset] < n_probes) {
+		if (n_probes > CK_HS_WORD_MAX)
+			n_probes = CK_HS_WORD_MAX;
+
+		CK_HS_STORE(&m->probe_bound[offset], n_probes);
+		ck_pr_fence_store();
+	}
+
+	return;
+}
+
+static inline unsigned int
+ck_hs_map_bound_get(struct ck_hs_map *m, unsigned long h)
+{
+	unsigned long offset = h & m->mask;
+	unsigned int r = CK_HS_WORD_MAX;
+
+	if (m->probe_bound != NULL) {
+		r = CK_HS_LOAD(&m->probe_bound[offset]);
+		if (r == CK_HS_WORD_MAX)
+			r = ck_pr_load_uint(&m->probe_maximum);
+	} else {
+		r = ck_pr_load_uint(&m->probe_maximum);
+	}
+
+	return r;
+}
+
+bool
+ck_hs_grow(struct ck_hs *hs,
+    unsigned long capacity)
+{
+	struct ck_hs_map *map, *update;
+	unsigned long k, i, j, offset, probes;
+	const void *previous, **bucket;
+
+restart:
+	map = hs->map;
+	if (map->capacity > capacity)
+		return false;
+
+	update = ck_hs_map_create(hs, capacity);
+	if (update == NULL)
+		return false;
+
+	for (k = 0; k < map->capacity; k++) {
+		unsigned long h;
+
+		previous = map->entries[k];
+		if (previous == CK_HS_EMPTY || previous == CK_HS_TOMBSTONE)
+			continue;
+
+#ifdef CK_HS_PP
+		if (hs->mode & CK_HS_MODE_OBJECT)
+			previous = CK_HS_VMA(previous);
+#endif
+
+		h = hs->hf(previous, hs->seed);
+		offset = h & update->mask;
+		i = probes = 0;
+
+		for (;;) {
+			bucket = (const void **)((uintptr_t)&update->entries[offset] & ~(CK_MD_CACHELINE - 1));
+
+			for (j = 0; j < CK_HS_PROBE_L1; j++) {
+				const void **cursor = bucket + ((j + offset) & (CK_HS_PROBE_L1 - 1));
+
+				if (probes++ == update->probe_limit)
+					break;
+
+				if (CK_CC_LIKELY(*cursor == CK_HS_EMPTY)) {
+					*cursor = map->entries[k];
+					update->n_entries++;
+
+					ck_hs_map_bound_set(update, h, probes);
+					break;
+				}
+			}
+
+			if (j < CK_HS_PROBE_L1)
+				break;
+
+			offset = ck_hs_map_probe_next(update, offset, h, i++, probes);
+		}
+
+		if (probes > update->probe_limit) {
+			/*
+			 * We have hit the probe limit, map needs to be even larger.
+			 */
+			ck_hs_map_destroy(hs->m, update, false);
+			capacity <<= 1;
+			goto restart;
+		}
+	}
+
+	ck_pr_fence_store();
+	ck_pr_store_ptr(&hs->map, update);
+	ck_hs_map_destroy(hs->m, map, true);
+	return true;
+}
+
+static void
+ck_hs_map_postinsert(struct ck_hs *hs, struct ck_hs_map *map)
+{
+
+	map->n_entries++;
+	if ((map->n_entries << 1) > map->capacity)
+		ck_hs_grow(hs, map->capacity << 1);
+
+	return;
+}
+
+bool
+ck_hs_rebuild(struct ck_hs *hs)
+{
+
+	return ck_hs_grow(hs, hs->map->capacity);
+}
+
+static const void **
+ck_hs_map_probe(struct ck_hs *hs,
+    struct ck_hs_map *map,
+    unsigned long *n_probes,
+    const void ***priority,
+    unsigned long h,
+    const void *key,
+    const void **object,
+    unsigned long probe_limit,
+    enum ck_hs_probe_behavior behavior)
+{
+	const void **bucket, **cursor, *k, *compare;
+	const void **pr = NULL;
+	unsigned long offset, j, i, probes, opl;
+
+#ifdef CK_HS_PP
+	/* If we are storing object pointers, then we may leverage pointer packing. */
+	unsigned long hv = 0;
+
+	if (hs->mode & CK_HS_MODE_OBJECT) {
+		hv = (h >> 25) & CK_HS_KEY_MASK;
+		compare = CK_HS_VMA(key);
+	} else {
+		compare = key;
+	}
+#else
+	compare = key;
+#endif
+
+	offset = h & map->mask;
+	*object = NULL;
+	i = probes = 0;
+
+	opl = probe_limit;
+	if (behavior == CK_HS_PROBE_INSERT)
+		probe_limit = ck_hs_map_bound_get(map, h);
+
+	for (;;) {
+		bucket = (const void **)((uintptr_t)&map->entries[offset] & ~(CK_MD_CACHELINE - 1));
+
+		for (j = 0; j < CK_HS_PROBE_L1; j++) {
+			cursor = bucket + ((j + offset) & (CK_HS_PROBE_L1 - 1));
+
+			if (probes++ == probe_limit) {
+				if (probe_limit == opl || pr != NULL) {
+					k = CK_HS_EMPTY;
+					goto leave;
+				}
+
+				/*
+				 * If no eligible slot has been found yet, continue probe
+				 * sequence with original probe limit.
+				 */
+				probe_limit = opl;
+			}
+
+			k = ck_pr_load_ptr(cursor);
+			if (k == CK_HS_EMPTY)
+				goto leave;
+
+			if (k == CK_HS_TOMBSTONE) {
+				if (pr == NULL) {
+					pr = cursor;
+					*n_probes = probes;
+
+					if (behavior == CK_HS_PROBE_TOMBSTONE) {
+						k = CK_HS_EMPTY;
+						goto leave;
+					}
+				}
+
+				continue;
+			}
+
+#ifdef CK_HS_PP
+			if (hs->mode & CK_HS_MODE_OBJECT) {
+				if (((uintptr_t)k >> CK_MD_VMA_BITS) != hv)
+					continue;
+
+				k = CK_HS_VMA(k);
+			}
+#endif
+
+			if (k == compare)
+				goto leave;
+
+			if (hs->compare == NULL)
+				continue;
+
+			if (hs->compare(k, key) == true)
+				goto leave;
+		}
+
+		offset = ck_hs_map_probe_next(map, offset, h, i++, probes);
+	}
+
+leave:
+	if (probes > probe_limit) {
+		cursor = NULL;
+	} else {
+		*object = k;
+	}
+
+	if (pr == NULL)
+		*n_probes = probes;
+
+	*priority = pr;
+	return cursor;
+}
+
+static inline const void *
+ck_hs_marshal(unsigned int mode, const void *key, unsigned long h)
+{
+#ifdef CK_HS_PP
+	const void *insert;
+
+	if (mode & CK_HS_MODE_OBJECT) {
+		insert = (void *)((uintptr_t)CK_HS_VMA(key) |
+		    ((h >> 25) << CK_MD_VMA_BITS));
+	} else {
+		insert = key;
+	}
+
+	return insert;
+#else
+	(void)mode;
+	(void)h;
+
+	return key;
+#endif
+}
+
+bool
+ck_hs_gc(struct ck_hs *hs, unsigned long cycles, unsigned long seed)
+{
+	unsigned long size = 0;
+	unsigned long i;
+	struct ck_hs_map *map = hs->map;
+	unsigned int maximum;
+	CK_HS_WORD *bounds = NULL;
+
+	if (map->n_entries == 0) {
+		ck_pr_store_uint(&map->probe_maximum, 0);
+		if (map->probe_bound != NULL)
+			memset(map->probe_bound, 0, sizeof(CK_HS_WORD) * map->capacity);
+
+		return true;
+	}
+
+	if (cycles == 0) {
+		maximum = 0;
+
+		if (map->probe_bound != NULL) {
+			size = sizeof(CK_HS_WORD) * map->capacity;
+			bounds = hs->m->malloc(size);
+			if (bounds == NULL)
+				return false;
+
+			memset(bounds, 0, size);
+		}
+	} else {
+		maximum = map->probe_maximum;
+	}
+
+	for (i = 0; i < map->capacity; i++) {
+		const void **first, *object, **slot, *entry;
+		unsigned long n_probes, offset, h;
+
+		entry = map->entries[(i + seed) & map->mask];
+		if (entry == CK_HS_EMPTY || entry == CK_HS_TOMBSTONE)
+			continue;
+
+#ifdef CK_HS_PP
+		if (hs->mode & CK_HS_MODE_OBJECT)
+			entry = CK_HS_VMA(entry);
+#endif
+
+		h = hs->hf(entry, hs->seed);
+		offset = h & map->mask;
+
+		slot = ck_hs_map_probe(hs, map, &n_probes, &first, h, entry, &object,
+		    ck_hs_map_bound_get(map, h), CK_HS_PROBE);
+
+		if (first != NULL) {
+			const void *insert = ck_hs_marshal(hs->mode, entry, h);
+
+			ck_pr_store_ptr(first, insert);
+			ck_hs_map_signal(map, h);
+			ck_pr_store_ptr(slot, CK_HS_TOMBSTONE);
+		}
+
+		if (cycles == 0) {
+			if (n_probes > maximum)
+				maximum = n_probes;
+
+			if (n_probes > CK_HS_WORD_MAX)
+				n_probes = CK_HS_WORD_MAX;
+
+			if (bounds != NULL && n_probes > bounds[offset])
+				bounds[offset] = n_probes;
+		} else if (--cycles == 0)
+			break;
+	}
+
+	/*
+	 * The following only apply to garbage collection involving
+	 * a full scan of all entries.
+	 */
+	if (maximum != map->probe_maximum)
+		ck_pr_store_uint(&map->probe_maximum, maximum);
+
+	if (bounds != NULL) {
+		for (i = 0; i < map->capacity; i++)
+			CK_HS_STORE(&map->probe_bound[i], bounds[i]);
+
+		hs->m->free(bounds, size, false);
+	}
+
+	return true;
+}
+
+bool
+ck_hs_fas(struct ck_hs *hs,
+    unsigned long h,
+    const void *key,
+    void **previous)
+{
+	const void **slot, **first, *object, *insert;
+	struct ck_hs_map *map = hs->map;
+	unsigned long n_probes;
+
+	*previous = NULL;
+	slot = ck_hs_map_probe(hs, map, &n_probes, &first, h, key, &object,
+	    ck_hs_map_bound_get(map, h), CK_HS_PROBE);
+
+	/* Replacement semantics presume existence. */
+	if (object == NULL)
+		return false;
+
+	insert = ck_hs_marshal(hs->mode, key, h);
+
+	if (first != NULL) {
+		ck_pr_store_ptr(first, insert);
+		ck_hs_map_signal(map, h);
+		ck_pr_store_ptr(slot, CK_HS_TOMBSTONE);
+	} else {
+		ck_pr_store_ptr(slot, insert);
+	}
+
+	*previous = CK_CC_DECONST_PTR(object);
+	return true;
+}
+
+/*
+ * An apply function takes two arguments. The first argument is a pointer to a
+ * pre-existing object. The second argument is a pointer to the fifth argument
+ * passed to ck_hs_apply. If a non-NULL pointer is passed to the first argument
+ * and the return value of the apply function is NULL, then the pre-existing
+ * value is deleted. If the return pointer is the same as the one passed to the
+ * apply function then no changes are made to the hash table.  If the first
+ * argument is non-NULL and the return pointer is different than that passed to
+ * the apply function, then the pre-existing value is replaced. For
+ * replacement, it is required that the value itself is identical to the
+ * previous value.
+ */
+bool
+ck_hs_apply(struct ck_hs *hs,
+    unsigned long h,
+    const void *key,
+    ck_hs_apply_fn_t *fn,
+    void *cl)
+{
+	const void **slot, **first, *object, *delta, *insert;
+	unsigned long n_probes;
+	struct ck_hs_map *map;
+
+restart:
+	map = hs->map;
+
+	slot = ck_hs_map_probe(hs, map, &n_probes, &first, h, key, &object, map->probe_limit, CK_HS_PROBE_INSERT);
+	if (slot == NULL && first == NULL) {
+		if (ck_hs_grow(hs, map->capacity << 1) == false)
+			return false;
+
+		goto restart;
+	}
+
+	delta = fn(CK_CC_DECONST_PTR(object), cl);
+	if (delta == NULL) {
+		/*
+		 * The apply function has requested deletion. If the object doesn't exist,
+		 * then exit early.
+		 */
+		if (CK_CC_UNLIKELY(object == NULL))
+			return true;
+
+		/* Otherwise, mark slot as deleted. */
+		ck_pr_store_ptr(slot, CK_HS_TOMBSTONE);
+		map->n_entries--;
+		map->tombstones++;
+		return true;
+	}
+
+	/* The apply function has not requested hash set modification so exit early. */
+	if (delta == object)
+		return true;
+
+	/* A modification or insertion has been requested. */
+	ck_hs_map_bound_set(map, h, n_probes);
+
+	insert = ck_hs_marshal(hs->mode, delta, h);
+	if (first != NULL) {
+		/*
+		 * This follows the same semantics as ck_hs_set, please refer to that
+		 * function for documentation.
+		 */
+		ck_pr_store_ptr(first, insert);
+
+		if (object != NULL) {
+			ck_hs_map_signal(map, h);
+			ck_pr_store_ptr(slot, CK_HS_TOMBSTONE);
+		}
+	} else {
+		/*
+		 * If we are storing into same slot, then atomic store is sufficient
+		 * for replacement.
+		 */
+		ck_pr_store_ptr(slot, insert);
+	}
+
+	if (object == NULL)
+		ck_hs_map_postinsert(hs, map);
+
+	return true;
+}
+
+bool
+ck_hs_set(struct ck_hs *hs,
+    unsigned long h,
+    const void *key,
+    void **previous)
+{
+	const void **slot, **first, *object, *insert;
+	unsigned long n_probes;
+	struct ck_hs_map *map;
+
+	*previous = NULL;
+
+restart:
+	map = hs->map;
+
+	slot = ck_hs_map_probe(hs, map, &n_probes, &first, h, key, &object, map->probe_limit, CK_HS_PROBE_INSERT);
+	if (slot == NULL && first == NULL) {
+		if (ck_hs_grow(hs, map->capacity << 1) == false)
+			return false;
+
+		goto restart;
+	}
+
+	ck_hs_map_bound_set(map, h, n_probes);
+	insert = ck_hs_marshal(hs->mode, key, h);
+
+	if (first != NULL) {
+		/* If an earlier bucket was found, then store entry there. */
+		ck_pr_store_ptr(first, insert);
+
+		/*
+		 * If a duplicate key was found, then delete it after
+		 * signaling concurrent probes to restart. Optionally,
+		 * it is possible to install tombstone after grace
+		 * period if we can guarantee earlier position of
+		 * duplicate key.
+		 */
+		if (object != NULL) {
+			ck_hs_map_signal(map, h);
+			ck_pr_store_ptr(slot, CK_HS_TOMBSTONE);
+		}
+	} else {
+		/*
+		 * If we are storing into same slot, then atomic store is sufficient
+		 * for replacement.
+		 */
+		ck_pr_store_ptr(slot, insert);
+	}
+
+	if (object == NULL)
+		ck_hs_map_postinsert(hs, map);
+
+	*previous = CK_CC_DECONST_PTR(object);
+	return true;
+}
+
+CK_CC_INLINE static bool
+ck_hs_put_internal(struct ck_hs *hs,
+    unsigned long h,
+    const void *key,
+    enum ck_hs_probe_behavior behavior)
+{
+	const void **slot, **first, *object, *insert;
+	unsigned long n_probes;
+	struct ck_hs_map *map;
+
+restart:
+	map = hs->map;
+
+	slot = ck_hs_map_probe(hs, map, &n_probes, &first, h, key, &object,
+	    map->probe_limit, behavior);
+
+	if (slot == NULL && first == NULL) {
+		if (ck_hs_grow(hs, map->capacity << 1) == false)
+			return false;
+
+		goto restart;
+	}
+
+	/* Fail operation if a match was found. */
+	if (object != NULL)
+		return false;
+
+	ck_hs_map_bound_set(map, h, n_probes);
+	insert = ck_hs_marshal(hs->mode, key, h);
+
+	if (first != NULL) {
+		/* Insert key into first bucket in probe sequence. */
+		ck_pr_store_ptr(first, insert);
+	} else {
+		/* An empty slot was found. */
+		ck_pr_store_ptr(slot, insert);
+	}
+
+	ck_hs_map_postinsert(hs, map);
+	return true;
+}
+
+bool
+ck_hs_put(struct ck_hs *hs,
+    unsigned long h,
+    const void *key)
+{
+
+	return ck_hs_put_internal(hs, h, key, CK_HS_PROBE_INSERT);
+}
+
+bool
+ck_hs_put_unique(struct ck_hs *hs,
+    unsigned long h,
+    const void *key)
+{
+
+	return ck_hs_put_internal(hs, h, key, CK_HS_PROBE_TOMBSTONE);
+}
+
+void *
+ck_hs_get(struct ck_hs *hs,
+    unsigned long h,
+    const void *key)
+{
+	const void **first, *object;
+	struct ck_hs_map *map;
+	unsigned long n_probes;
+	unsigned int g, g_p, probe;
+	unsigned int *generation;
+
+	do {
+		map = ck_pr_load_ptr(&hs->map);
+		generation = &map->generation[h & CK_HS_G_MASK];
+		g = ck_pr_load_uint(generation);
+		probe  = ck_hs_map_bound_get(map, h);
+		ck_pr_fence_load();
+
+		ck_hs_map_probe(hs, map, &n_probes, &first, h, key, &object, probe, CK_HS_PROBE);
+
+		ck_pr_fence_load();
+		g_p = ck_pr_load_uint(generation);
+	} while (g != g_p);
+
+	return CK_CC_DECONST_PTR(object);
+}
+
+void *
+ck_hs_remove(struct ck_hs *hs,
+    unsigned long h,
+    const void *key)
+{
+	const void **slot, **first, *object;
+	struct ck_hs_map *map = hs->map;
+	unsigned long n_probes;
+
+	slot = ck_hs_map_probe(hs, map, &n_probes, &first, h, key, &object,
+	    ck_hs_map_bound_get(map, h), CK_HS_PROBE);
+	if (object == NULL)
+		return NULL;
+
+	ck_pr_store_ptr(slot, CK_HS_TOMBSTONE);
+	map->n_entries--;
+	map->tombstones++;
+	return CK_CC_DECONST_PTR(object);
+}
+
+bool
+ck_hs_move(struct ck_hs *hs,
+    struct ck_hs *source,
+    ck_hs_hash_cb_t *hf,
+    ck_hs_compare_cb_t *compare,
+    struct ck_malloc *m)
+{
+
+	if (m == NULL || m->malloc == NULL || m->free == NULL || hf == NULL)
+		return false;
+
+	hs->mode = source->mode;
+	hs->seed = source->seed;
+	hs->map = source->map;
+	hs->m = m;
+	hs->hf = hf;
+	hs->compare = compare;
+	return true;
+}
+
+bool
+ck_hs_init(struct ck_hs *hs,
+    unsigned int mode,
+    ck_hs_hash_cb_t *hf,
+    ck_hs_compare_cb_t *compare,
+    struct ck_malloc *m,
+    unsigned long n_entries,
+    unsigned long seed)
+{
+
+	if (m == NULL || m->malloc == NULL || m->free == NULL || hf == NULL)
+		return false;
+
+	hs->m = m;
+	hs->mode = mode;
+	hs->seed = seed;
+	hs->hf = hf;
+	hs->compare = compare;
+
+	hs->map = ck_hs_map_create(hs, n_entries);
+	return hs->map != NULL;
+}
diff --git a/src/ck_ht.c b/src/ck_ht.c
new file mode 100644
index 0000000..2c864c5
--- /dev/null
+++ b/src/ck_ht.c
@@ -0,0 +1,1036 @@
+/*
+ * Copyright 2012-2015 Samy Al Bahra.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#define CK_HT_IM
+#include <ck_ht.h>
+
+/*
+ * This implementation borrows several techniques from Josh Dybnis's
+ * nbds library which can be found at http://code.google.com/p/nbds
+ *
+ * This release currently only includes support for 64-bit platforms.
+ * We can address 32-bit platforms in a future release.
+ */
+#include <ck_cc.h>
+#include <ck_md.h>
+#include <ck_pr.h>
+#include <ck_stdint.h>
+#include <ck_stdbool.h>
+#include <ck_string.h>
+
+#include "ck_ht_hash.h"
+#include "ck_internal.h"
+
+#ifndef CK_HT_BUCKET_LENGTH
+
+#ifdef CK_HT_PP
+#define CK_HT_BUCKET_SHIFT 2ULL
+#else
+#define CK_HT_BUCKET_SHIFT 1ULL
+#endif
+
+#define CK_HT_BUCKET_LENGTH (1U << CK_HT_BUCKET_SHIFT)
+#define CK_HT_BUCKET_MASK (CK_HT_BUCKET_LENGTH - 1)
+#endif
+
+#ifndef CK_HT_PROBE_DEFAULT
+#define CK_HT_PROBE_DEFAULT 64ULL
+#endif
+
+#if defined(CK_F_PR_LOAD_8) && defined(CK_F_PR_STORE_8)
+#define CK_HT_WORD	    uint8_t
+#define CK_HT_WORD_MAX	    UINT8_MAX
+#define CK_HT_STORE(x, y)   ck_pr_store_8(x, y)
+#define CK_HT_LOAD(x)	    ck_pr_load_8(x)
+#elif defined(CK_F_PR_LOAD_16) && defined(CK_F_PR_STORE_16)
+#define CK_HT_WORD	    uint16_t
+#define CK_HT_WORD_MAX	    UINT16_MAX
+#define CK_HT_STORE(x, y)   ck_pr_store_16(x, y)
+#define CK_HT_LOAD(x)	    ck_pr_load_16(x)
+#elif defined(CK_F_PR_LOAD_32) && defined(CK_F_PR_STORE_32)
+#define CK_HT_WORD	    uint32_t
+#define CK_HT_WORD_MAX	    UINT32_MAX
+#define CK_HT_STORE(x, y)   ck_pr_store_32(x, y)
+#define CK_HT_LOAD(x)	    ck_pr_load_32(x)
+#else
+#error "ck_ht is not supported on your platform."
+#endif
+
+struct ck_ht_map {
+	unsigned int mode;
+	CK_HT_TYPE deletions;
+	CK_HT_TYPE probe_maximum;
+	CK_HT_TYPE probe_length;
+	CK_HT_TYPE probe_limit;
+	CK_HT_TYPE size;
+	CK_HT_TYPE n_entries;
+	CK_HT_TYPE mask;
+	CK_HT_TYPE capacity;
+	CK_HT_TYPE step;
+	CK_HT_WORD *probe_bound;
+	struct ck_ht_entry *entries;
+};
+
+void
+ck_ht_stat(struct ck_ht *table,
+    struct ck_ht_stat *st)
+{
+	struct ck_ht_map *map = table->map;
+
+	st->n_entries = map->n_entries;
+	st->probe_maximum = map->probe_maximum;
+	return;
+}
+
+void
+ck_ht_hash(struct ck_ht_hash *h,
+    struct ck_ht *table,
+    const void *key,
+    uint16_t key_length)
+{
+
+	table->h(h, key, key_length, table->seed);
+	return;
+}
+
+void
+ck_ht_hash_direct(struct ck_ht_hash *h,
+    struct ck_ht *table,
+    uintptr_t key)
+{
+
+	ck_ht_hash(h, table, &key, sizeof(key));
+	return;
+}
+
+static void
+ck_ht_hash_wrapper(struct ck_ht_hash *h,
+    const void *key,
+    size_t length,
+    uint64_t seed)
+{
+
+	h->value = (unsigned long)MurmurHash64A(key, length, seed);
+	return;
+}
+
+static struct ck_ht_map *
+ck_ht_map_create(struct ck_ht *table, CK_HT_TYPE entries)
+{
+	struct ck_ht_map *map;
+	CK_HT_TYPE size;
+	uintptr_t prefix;
+	uint32_t n_entries;
+
+	n_entries = ck_internal_power_2(entries);
+	if (n_entries < CK_HT_BUCKET_LENGTH)
+		n_entries = CK_HT_BUCKET_LENGTH;
+
+	size = sizeof(struct ck_ht_map) +
+		   (sizeof(struct ck_ht_entry) * n_entries + CK_MD_CACHELINE - 1);
+
+	if (table->mode & CK_HT_WORKLOAD_DELETE) {
+		prefix = sizeof(CK_HT_WORD) * n_entries;
+		size += prefix;
+	} else {
+		prefix = 0;
+	}
+
+	map = table->m->malloc(size);
+	if (map == NULL)
+		return NULL;
+
+	map->mode = table->mode;
+	map->size = size;
+	map->probe_limit = ck_internal_max_64(n_entries >>
+	    (CK_HT_BUCKET_SHIFT + 2), CK_HT_PROBE_DEFAULT);
+
+	map->deletions = 0;
+	map->probe_maximum = 0;
+	map->capacity = n_entries;
+	map->step = ck_internal_bsf_64(map->capacity);
+	map->mask = map->capacity - 1;
+	map->n_entries = 0;
+	map->entries = (struct ck_ht_entry *)(((uintptr_t)&map[1] + prefix +
+	    CK_MD_CACHELINE - 1) & ~(CK_MD_CACHELINE - 1));
+
+	if (table->mode & CK_HT_WORKLOAD_DELETE) {
+		map->probe_bound = (CK_HT_WORD *)&map[1];
+		memset(map->probe_bound, 0, prefix);
+	} else {
+		map->probe_bound = NULL;
+	}
+
+	memset(map->entries, 0, sizeof(struct ck_ht_entry) * n_entries);
+	ck_pr_fence_store();
+	return map;
+}
+
+static inline void
+ck_ht_map_bound_set(struct ck_ht_map *m,
+    struct ck_ht_hash h,
+    CK_HT_TYPE n_probes)
+{
+	CK_HT_TYPE offset = h.value & m->mask;
+
+	if (n_probes > m->probe_maximum)
+		CK_HT_TYPE_STORE(&m->probe_maximum, n_probes);
+
+	if (m->probe_bound != NULL && m->probe_bound[offset] < n_probes) {
+		if (n_probes >= CK_HT_WORD_MAX)
+			n_probes = CK_HT_WORD_MAX;
+
+		CK_HT_STORE(&m->probe_bound[offset], n_probes);
+		ck_pr_fence_store();
+	}
+
+	return;
+}
+
+static inline CK_HT_TYPE
+ck_ht_map_bound_get(struct ck_ht_map *m, struct ck_ht_hash h)
+{
+	CK_HT_TYPE offset = h.value & m->mask;
+	CK_HT_TYPE r = CK_HT_WORD_MAX;
+
+	if (m->probe_bound != NULL) {
+		r = CK_HT_LOAD(&m->probe_bound[offset]);
+		if (r == CK_HT_WORD_MAX)
+			r = CK_HT_TYPE_LOAD(&m->probe_maximum);
+	} else {
+		r = CK_HT_TYPE_LOAD(&m->probe_maximum);
+	}
+
+	return r;
+}
+
+static void
+ck_ht_map_destroy(struct ck_malloc *m, struct ck_ht_map *map, bool defer)
+{
+
+	m->free(map, map->size, defer);
+	return;
+}
+
+static inline size_t
+ck_ht_map_probe_next(struct ck_ht_map *map, size_t offset, ck_ht_hash_t h, size_t probes)
+{
+	ck_ht_hash_t r;
+	size_t stride;
+	unsigned long level = (unsigned long)probes >> CK_HT_BUCKET_SHIFT;
+
+	r.value = (h.value >> map->step) >> level;
+	stride = (r.value & ~CK_HT_BUCKET_MASK) << 1
+		     | (r.value & CK_HT_BUCKET_MASK);
+
+	return (offset + level +
+	    (stride | CK_HT_BUCKET_LENGTH)) & map->mask;
+}
+
+bool
+ck_ht_init(struct ck_ht *table,
+    unsigned int mode,
+    ck_ht_hash_cb_t *h,
+    struct ck_malloc *m,
+    CK_HT_TYPE entries,
+    uint64_t seed)
+{
+
+	if (m == NULL || m->malloc == NULL || m->free == NULL)
+		return false;
+
+	table->m = m;
+	table->mode = mode;
+	table->seed = seed;
+
+	if (h == NULL) {
+		table->h = ck_ht_hash_wrapper;
+	} else {
+		table->h = h;
+	}
+
+	table->map = ck_ht_map_create(table, entries);
+	return table->map != NULL;
+}
+
+static struct ck_ht_entry *
+ck_ht_map_probe_wr(struct ck_ht_map *map,
+    ck_ht_hash_t h,
+    ck_ht_entry_t *snapshot,
+    ck_ht_entry_t **available,
+    const void *key,
+    uint16_t key_length,
+    CK_HT_TYPE *probe_limit,
+    CK_HT_TYPE *probe_wr)
+{
+	struct ck_ht_entry *bucket, *cursor;
+	struct ck_ht_entry *first = NULL;
+	size_t offset, i, j;
+	CK_HT_TYPE probes = 0;
+	CK_HT_TYPE limit;
+
+	if (probe_limit == NULL) {
+		limit = ck_ht_map_bound_get(map, h);
+	} else {
+		limit = CK_HT_TYPE_MAX;
+	}
+
+	offset = h.value & map->mask;
+	for (i = 0; i < map->probe_limit; i++) {
+		/*
+		 * Probe on a complete cache line first. Scan forward and wrap around to
+		 * the beginning of the cache line. Only when the complete cache line has
+		 * been scanned do we move on to the next row.
+		 */
+		bucket = (void *)((uintptr_t)(map->entries + offset) &
+			     ~(CK_MD_CACHELINE - 1));
+
+		for (j = 0; j < CK_HT_BUCKET_LENGTH; j++) {
+			uint16_t k;
+
+			if (probes++ > limit)
+				break;
+
+			cursor = bucket + ((j + offset) & (CK_HT_BUCKET_LENGTH - 1));
+
+			/*
+			 * It is probably worth it to encapsulate probe state
+			 * in order to prevent a complete reprobe sequence in
+			 * the case of intermittent writers.
+			 */
+			if (cursor->key == CK_HT_KEY_TOMBSTONE) {
+				if (first == NULL) {
+					first = cursor;
+					*probe_wr = probes;
+				}
+
+				continue;
+			}
+
+			if (cursor->key == CK_HT_KEY_EMPTY)
+				goto leave;
+
+			if (cursor->key == (uintptr_t)key)
+				goto leave;
+
+			if (map->mode & CK_HT_MODE_BYTESTRING) {
+				void *pointer;
+
+				/*
+				 * Check memoized portion of hash value before
+				 * expensive full-length comparison.
+				 */
+				k = ck_ht_entry_key_length(cursor);
+				if (k != key_length)
+					continue;
+
+#ifdef CK_HT_PP
+				if ((cursor->value >> CK_MD_VMA_BITS) != ((h.value >> 32) & CK_HT_KEY_MASK))
+					continue;
+#else
+				if (cursor->hash != h.value)
+					continue;
+#endif
+
+				pointer = ck_ht_entry_key(cursor);
+				if (memcmp(pointer, key, key_length) == 0)
+					goto leave;
+			}
+		}
+
+		offset = ck_ht_map_probe_next(map, offset, h, probes);
+	}
+
+	cursor = NULL;
+
+leave:
+	if (probe_limit != NULL) {
+		*probe_limit = probes;
+	} else if (first == NULL) {
+		*probe_wr = probes;
+	}
+
+	*available = first;
+
+	if (cursor != NULL) {
+		*snapshot = *cursor;
+	}
+
+	return cursor;
+}
+
+bool
+ck_ht_gc(struct ck_ht *ht, unsigned long cycles, unsigned long seed)
+{
+	CK_HT_WORD *bounds = NULL;
+	struct ck_ht_map *map = ht->map;
+	CK_HT_TYPE maximum, i;
+	CK_HT_TYPE size = 0;
+
+	if (map->n_entries == 0) {
+		CK_HT_TYPE_STORE(&map->probe_maximum, 0);
+		if (map->probe_bound != NULL)
+			memset(map->probe_bound, 0, sizeof(CK_HT_WORD) * map->capacity);
+
+		return true;
+	}
+
+	if (cycles == 0) {
+		maximum = 0;
+
+		if (map->probe_bound != NULL) {
+			size = sizeof(CK_HT_WORD) * map->capacity;
+			bounds = ht->m->malloc(size);
+			if (bounds == NULL)
+				return false;
+
+			memset(bounds, 0, size);
+		}
+	} else {
+		maximum = map->probe_maximum;
+	}
+
+	for (i = 0; i < map->capacity; i++) {
+		struct ck_ht_entry *entry, *priority, snapshot;
+		struct ck_ht_hash h;
+		CK_HT_TYPE probes_wr;
+		CK_HT_TYPE offset;
+
+		entry = &map->entries[(i + seed) & map->mask];
+		if (entry->key == CK_HT_KEY_EMPTY ||
+		    entry->key == CK_HT_KEY_TOMBSTONE) {
+			continue;
+		}
+
+		if (ht->mode & CK_HT_MODE_BYTESTRING) {
+#ifndef CK_HT_PP
+			h.value = entry->hash;
+#else
+			ht->h(&h, ck_ht_entry_key(entry), ck_ht_entry_key_length(entry),
+			    ht->seed);
+#endif
+			entry = ck_ht_map_probe_wr(map, h, &snapshot, &priority,
+			    ck_ht_entry_key(entry),
+			    ck_ht_entry_key_length(entry),
+			    NULL, &probes_wr);
+		} else {
+#ifndef CK_HT_PP
+			h.value = entry->hash;
+#else
+			ht->h(&h, &entry->key, sizeof(entry->key), ht->seed);
+#endif
+			entry = ck_ht_map_probe_wr(map, h, &snapshot, &priority,
+			    (void *)entry->key,
+			    sizeof(entry->key),
+			    NULL, &probes_wr);
+		}
+
+		offset = h.value & map->mask;
+
+		if (priority != NULL) {
+			CK_HT_TYPE_STORE(&map->deletions, map->deletions + 1);
+			ck_pr_fence_store();
+#ifndef CK_HT_PP
+			CK_HT_TYPE_STORE(&priority->key_length, entry->key_length);
+			CK_HT_TYPE_STORE(&priority->hash, entry->hash);
+#endif
+			ck_pr_store_ptr_unsafe(&priority->value, (void *)entry->value);
+			ck_pr_fence_store();
+			ck_pr_store_ptr_unsafe(&priority->key, (void *)entry->key);
+			ck_pr_fence_store();
+			CK_HT_TYPE_STORE(&map->deletions, map->deletions + 1);
+			ck_pr_fence_store();
+			ck_pr_store_ptr_unsafe(&entry->key, (void *)CK_HT_KEY_TOMBSTONE);
+			ck_pr_fence_store();
+		}
+
+		if (cycles == 0) {
+			if (probes_wr > maximum)
+				maximum = probes_wr;
+
+			if (probes_wr >= CK_HT_WORD_MAX)
+				probes_wr = CK_HT_WORD_MAX;
+
+			if (bounds != NULL && probes_wr > bounds[offset])
+				bounds[offset] = probes_wr;
+		} else if (--cycles == 0)
+			break;
+	}
+
+	if (maximum != map->probe_maximum)
+		CK_HT_TYPE_STORE(&map->probe_maximum, maximum);
+
+	if (bounds != NULL) {
+		for (i = 0; i < map->capacity; i++)
+			CK_HT_STORE(&map->probe_bound[i], bounds[i]);
+
+		ht->m->free(bounds, size, false);
+	}
+
+	return true;
+}
+
+static struct ck_ht_entry *
+ck_ht_map_probe_rd(struct ck_ht_map *map,
+    ck_ht_hash_t h,
+    ck_ht_entry_t *snapshot,
+    const void *key,
+    uint16_t key_length)
+{
+	struct ck_ht_entry *bucket, *cursor;
+	size_t offset, i, j;
+	CK_HT_TYPE probes = 0;
+	CK_HT_TYPE probe_maximum;
+
+#ifndef CK_HT_PP
+	CK_HT_TYPE d = 0;
+	CK_HT_TYPE d_prime = 0;
+retry:
+#endif
+
+	probe_maximum = ck_ht_map_bound_get(map, h);
+	offset = h.value & map->mask;
+
+	for (i = 0; i < map->probe_limit; i++) {
+		/*
+		 * Probe on a complete cache line first. Scan forward and wrap around to
+		 * the beginning of the cache line. Only when the complete cache line has
+		 * been scanned do we move on to the next row.
+		 */
+		bucket = (void *)((uintptr_t)(map->entries + offset) &
+			     ~(CK_MD_CACHELINE - 1));
+
+		for (j = 0; j < CK_HT_BUCKET_LENGTH; j++) {
+			uint16_t k;
+
+			if (probes++ > probe_maximum)
+				return NULL;
+
+			cursor = bucket + ((j + offset) & (CK_HT_BUCKET_LENGTH - 1));
+
+#ifdef CK_HT_PP
+			snapshot->key = (uintptr_t)ck_pr_load_ptr(&cursor->key);
+			ck_pr_fence_load();
+			snapshot->value = (uintptr_t)ck_pr_load_ptr(&cursor->value);
+#else
+			d = CK_HT_TYPE_LOAD(&map->deletions);
+			snapshot->key = (uintptr_t)ck_pr_load_ptr(&cursor->key);
+			ck_pr_fence_load();
+			snapshot->key_length = CK_HT_TYPE_LOAD(&cursor->key_length);
+			snapshot->hash = CK_HT_TYPE_LOAD(&cursor->hash);
+			snapshot->value = (uintptr_t)ck_pr_load_ptr(&cursor->value);
+#endif
+
+			/*
+			 * It is probably worth it to encapsulate probe state
+			 * in order to prevent a complete reprobe sequence in
+			 * the case of intermittent writers.
+			 */
+			if (snapshot->key == CK_HT_KEY_TOMBSTONE)
+				continue;
+
+			if (snapshot->key == CK_HT_KEY_EMPTY)
+				goto leave;
+
+			if (snapshot->key == (uintptr_t)key)
+				goto leave;
+
+			if (map->mode & CK_HT_MODE_BYTESTRING) {
+				void *pointer;
+
+				/*
+				 * Check memoized portion of hash value before
+				 * expensive full-length comparison.
+				 */
+				k = ck_ht_entry_key_length(snapshot);
+				if (k != key_length)
+					continue;
+#ifdef CK_HT_PP
+				if ((snapshot->value >> CK_MD_VMA_BITS) != ((h.value >> 32) & CK_HT_KEY_MASK))
+					continue;
+#else
+				if (snapshot->hash != h.value)
+					continue;
+
+				d_prime = CK_HT_TYPE_LOAD(&map->deletions);
+
+				/*
+				 * It is possible that the slot was
+				 * replaced, initiate a re-probe.
+				 */
+				if (d != d_prime)
+					goto retry;
+#endif
+
+				pointer = ck_ht_entry_key(snapshot);
+				if (memcmp(pointer, key, key_length) == 0)
+					goto leave;
+			}
+		}
+
+		offset = ck_ht_map_probe_next(map, offset, h, probes);
+	}
+
+	return NULL;
+
+leave:
+	return cursor;
+}
+
+CK_HT_TYPE
+ck_ht_count(struct ck_ht *table)
+{
+	struct ck_ht_map *map = ck_pr_load_ptr(&table->map);
+
+	return CK_HT_TYPE_LOAD(&map->n_entries);
+}
+
+bool
+ck_ht_next(struct ck_ht *table,
+    struct ck_ht_iterator *i,
+    struct ck_ht_entry **entry)
+{
+	struct ck_ht_map *map = table->map;
+	uintptr_t key;
+
+	if (i->offset >= map->capacity)
+		return false;
+
+	do {
+		key = map->entries[i->offset].key;
+		if (key != CK_HT_KEY_EMPTY && key != CK_HT_KEY_TOMBSTONE)
+			break;
+	} while (++i->offset < map->capacity);
+
+	if (i->offset >= map->capacity)
+		return false;
+
+	*entry = map->entries + i->offset++;
+	return true;
+}
+
+bool
+ck_ht_reset_size_spmc(struct ck_ht *table, CK_HT_TYPE size)
+{
+	struct ck_ht_map *map, *update;
+
+	map = table->map;
+	update = ck_ht_map_create(table, size);
+	if (update == NULL)
+		return false;
+
+	ck_pr_store_ptr_unsafe(&table->map, update);
+	ck_ht_map_destroy(table->m, map, true);
+	return true;
+}
+
+bool
+ck_ht_reset_spmc(struct ck_ht *table)
+{
+	struct ck_ht_map *map = table->map;
+
+	return ck_ht_reset_size_spmc(table, map->capacity);
+}
+
+bool
+ck_ht_grow_spmc(struct ck_ht *table, CK_HT_TYPE capacity)
+{
+	struct ck_ht_map *map, *update;
+	struct ck_ht_entry *bucket, *previous;
+	struct ck_ht_hash h;
+	size_t k, i, j, offset;
+	CK_HT_TYPE probes;
+
+restart:
+	map = table->map;
+
+	if (map->capacity >= capacity)
+		return false;
+
+	update = ck_ht_map_create(table, capacity);
+	if (update == NULL)
+		return false;
+
+	for (k = 0; k < map->capacity; k++) {
+		previous = &map->entries[k];
+
+		if (previous->key == CK_HT_KEY_EMPTY || previous->key == CK_HT_KEY_TOMBSTONE)
+			continue;
+
+		if (table->mode & CK_HT_MODE_BYTESTRING) {
+#ifdef CK_HT_PP
+			void *key;
+			uint16_t key_length;
+
+			key = ck_ht_entry_key(previous);
+			key_length = ck_ht_entry_key_length(previous);
+#endif
+
+#ifndef CK_HT_PP
+			h.value = previous->hash;
+#else
+			table->h(&h, key, key_length, table->seed);
+#endif
+		} else {
+#ifndef CK_HT_PP
+			h.value = previous->hash;
+#else
+			table->h(&h, &previous->key, sizeof(previous->key), table->seed);
+#endif
+		}
+
+		offset = h.value & update->mask;
+		probes = 0;
+
+		for (i = 0; i < update->probe_limit; i++) {
+			bucket = (void *)((uintptr_t)(update->entries + offset) & ~(CK_MD_CACHELINE - 1));
+
+			for (j = 0; j < CK_HT_BUCKET_LENGTH; j++) {
+				struct ck_ht_entry *cursor = bucket + ((j + offset) & (CK_HT_BUCKET_LENGTH - 1));
+
+				probes++;
+				if (CK_CC_LIKELY(cursor->key == CK_HT_KEY_EMPTY)) {
+					*cursor = *previous;
+					update->n_entries++;
+					ck_ht_map_bound_set(update, h, probes);
+					break;
+				}
+			}
+
+			if (j < CK_HT_BUCKET_LENGTH)
+				break;
+
+			offset = ck_ht_map_probe_next(update, offset, h, probes);
+		}
+
+		if (i == update->probe_limit) {
+			/*
+			 * We have hit the probe limit, the map needs to be even
+			 * larger.
+			 */
+			ck_ht_map_destroy(table->m, update, false);
+			capacity <<= 1;
+			goto restart;
+		}
+	}
+
+	ck_pr_fence_store();
+	ck_pr_store_ptr_unsafe(&table->map, update);
+	ck_ht_map_destroy(table->m, map, true);
+	return true;
+}
+
+bool
+ck_ht_remove_spmc(struct ck_ht *table,
+    ck_ht_hash_t h,
+    ck_ht_entry_t *entry)
+{
+	struct ck_ht_map *map;
+	struct ck_ht_entry *candidate, snapshot;
+
+	map = table->map;
+
+	if (table->mode & CK_HT_MODE_BYTESTRING) {
+		candidate = ck_ht_map_probe_rd(map, h, &snapshot,
+		    ck_ht_entry_key(entry),
+		    ck_ht_entry_key_length(entry));
+	} else {
+		candidate = ck_ht_map_probe_rd(map, h, &snapshot,
+		    (void *)entry->key,
+		    sizeof(entry->key));
+	}
+
+	/* No matching entry was found. */
+	if (candidate == NULL || snapshot.key == CK_HT_KEY_EMPTY)
+		return false;
+
+	*entry = snapshot;
+
+	ck_pr_store_ptr_unsafe(&candidate->key, (void *)CK_HT_KEY_TOMBSTONE);
+	ck_pr_fence_store();
+	CK_HT_TYPE_STORE(&map->n_entries, map->n_entries - 1);
+	return true;
+}
+
+bool
+ck_ht_get_spmc(struct ck_ht *table,
+    ck_ht_hash_t h,
+    ck_ht_entry_t *entry)
+{
+	struct ck_ht_entry *candidate, snapshot;
+	struct ck_ht_map *map;
+	CK_HT_TYPE d, d_prime;
+
+restart:
+	map = ck_pr_load_ptr(&table->map);
+
+	/*
+	 * Platforms that cannot read key and key_length atomically must reprobe
+	 * on the scan of any single entry.
+	 */
+	d = CK_HT_TYPE_LOAD(&map->deletions);
+
+	if (table->mode & CK_HT_MODE_BYTESTRING) {
+		candidate = ck_ht_map_probe_rd(map, h, &snapshot,
+		    ck_ht_entry_key(entry), ck_ht_entry_key_length(entry));
+	} else {
+		candidate = ck_ht_map_probe_rd(map, h, &snapshot,
+		    (void *)entry->key, sizeof(entry->key));
+	}
+
+	d_prime = CK_HT_TYPE_LOAD(&map->deletions);
+	if (d != d_prime) {
+		/*
+		 * It is possible we have read (K, V'). Only valid states are
+		 * (K, V), (K', V') and (T, V). Restart load operation in face
+		 * of concurrent deletions or replacements.
+		 */
+		goto restart;
+	}
+
+	if (candidate == NULL || snapshot.key == CK_HT_KEY_EMPTY)
+		return false;
+
+	*entry = snapshot;
+	return true;
+}
+
+bool
+ck_ht_set_spmc(struct ck_ht *table,
+    ck_ht_hash_t h,
+    ck_ht_entry_t *entry)
+{
+	struct ck_ht_entry snapshot, *candidate, *priority;
+	struct ck_ht_map *map;
+	CK_HT_TYPE probes, probes_wr;
+	bool empty = false;
+
+	for (;;) {
+		map = table->map;
+
+		if (table->mode & CK_HT_MODE_BYTESTRING) {
+			candidate = ck_ht_map_probe_wr(map, h, &snapshot, &priority,
+			    ck_ht_entry_key(entry),
+			    ck_ht_entry_key_length(entry),
+			    &probes, &probes_wr);
+		} else {
+			candidate = ck_ht_map_probe_wr(map, h, &snapshot, &priority,
+			    (void *)entry->key,
+			    sizeof(entry->key),
+			    &probes, &probes_wr);
+		}
+
+		if (priority != NULL) {
+			probes = probes_wr;
+			break;
+		}
+
+		if (candidate != NULL)
+			break;
+
+		if (ck_ht_grow_spmc(table, map->capacity << 1) == false)
+			return false;
+	}
+
+	if (candidate == NULL) {
+		candidate = priority;
+		empty = true;
+	}
+
+	if (candidate->key != CK_HT_KEY_EMPTY &&
+	    priority != NULL && candidate != priority) {
+		/*
+		 * Entry is moved into another position in probe sequence.
+		 * We avoid a state of (K, B) (where [K, B] -> [K', B]) by
+		 * guaranteeing a forced reprobe before transitioning from K to
+		 * T. (K, B) implies (K, B, D') so we will reprobe successfully
+		 * from this transient state.
+		 */
+		probes = probes_wr;
+
+#ifndef CK_HT_PP
+		CK_HT_TYPE_STORE(&priority->key_length, entry->key_length);
+		CK_HT_TYPE_STORE(&priority->hash, entry->hash);
+#endif
+
+		/*
+		 * Readers must observe version counter change before they
+		 * observe re-use. If they observe re-use, it is at most
+		 * a tombstone.
+		 */
+		if (priority->value == CK_HT_KEY_TOMBSTONE) {
+			CK_HT_TYPE_STORE(&map->deletions, map->deletions + 1);
+			ck_pr_fence_store();
+		}
+
+		ck_pr_store_ptr_unsafe(&priority->value, (void *)entry->value);
+		ck_pr_fence_store();
+		ck_pr_store_ptr_unsafe(&priority->key, (void *)entry->key);
+		ck_pr_fence_store();
+
+		/*
+		 * Make sure that readers who observe the tombstone would
+		 * also observe counter change.
+		 */
+		CK_HT_TYPE_STORE(&map->deletions, map->deletions + 1);
+		ck_pr_fence_store();
+
+		ck_pr_store_ptr_unsafe(&candidate->key, (void *)CK_HT_KEY_TOMBSTONE);
+		ck_pr_fence_store();
+	} else {
+		/*
+		 * In this case we are inserting a new entry or replacing
+		 * an existing entry. Yes, this can be combined into above branch,
+		 * but isn't because you are actually looking at dying code
+		 * (ck_ht is effectively deprecated and is being replaced soon).
+		 */
+		bool replace = candidate->key != CK_HT_KEY_EMPTY &&
+		    candidate->key != CK_HT_KEY_TOMBSTONE;
+
+		if (priority != NULL) {
+			if (priority->key == CK_HT_KEY_TOMBSTONE) {
+				CK_HT_TYPE_STORE(&map->deletions, map->deletions + 1);
+				ck_pr_fence_store();
+			}
+
+			candidate = priority;
+			probes = probes_wr;
+		}
+
+#ifdef CK_HT_PP
+		ck_pr_store_ptr_unsafe(&candidate->value, (void *)entry->value);
+		ck_pr_fence_store();
+		ck_pr_store_ptr_unsafe(&candidate->key, (void *)entry->key);
+#else
+		CK_HT_TYPE_STORE(&candidate->key_length, entry->key_length);
+		CK_HT_TYPE_STORE(&candidate->hash, entry->hash);
+		ck_pr_store_ptr_unsafe(&candidate->value, (void *)entry->value);
+		ck_pr_fence_store();
+		ck_pr_store_ptr_unsafe(&candidate->key, (void *)entry->key);
+#endif
+
+		/*
+		 * If we are insert a new entry then increment number
+		 * of entries associated with map.
+		 */
+		if (replace == false)
+			CK_HT_TYPE_STORE(&map->n_entries, map->n_entries + 1);
+	}
+
+	ck_ht_map_bound_set(map, h, probes);
+
+	/* Enforce a load factor of 0.5. */
+	if (map->n_entries * 2 > map->capacity)
+		ck_ht_grow_spmc(table, map->capacity << 1);
+
+	if (empty == true) {
+		entry->key = CK_HT_KEY_EMPTY;
+	} else {
+		*entry = snapshot;
+	}
+
+	return true;
+}
+
+bool
+ck_ht_put_spmc(struct ck_ht *table,
+    ck_ht_hash_t h,
+    ck_ht_entry_t *entry)
+{
+	struct ck_ht_entry snapshot, *candidate, *priority;
+	struct ck_ht_map *map;
+	CK_HT_TYPE probes, probes_wr;
+
+	for (;;) {
+		map = table->map;
+
+		if (table->mode & CK_HT_MODE_BYTESTRING) {
+			candidate = ck_ht_map_probe_wr(map, h, &snapshot, &priority,
+			    ck_ht_entry_key(entry),
+			    ck_ht_entry_key_length(entry),
+			    &probes, &probes_wr);
+		} else {
+			candidate = ck_ht_map_probe_wr(map, h, &snapshot, &priority,
+			    (void *)entry->key,
+			    sizeof(entry->key),
+			    &probes, &probes_wr);
+		}
+
+		if (candidate != NULL || priority != NULL)
+			break;
+
+		if (ck_ht_grow_spmc(table, map->capacity << 1) == false)
+			return false;
+	}
+
+	if (priority != NULL) {
+		/* Version counter is updated before re-use. */
+		CK_HT_TYPE_STORE(&map->deletions, map->deletions + 1);
+		ck_pr_fence_store();
+
+		/* Re-use tombstone if one was found. */
+		candidate = priority;
+		probes = probes_wr;
+	} else if (candidate->key != CK_HT_KEY_EMPTY &&
+	    candidate->key != CK_HT_KEY_TOMBSTONE) {
+		/*
+		 * If the snapshot key is non-empty and the value field is not
+		 * a tombstone then an identical key was found. As store does
+		 * not implement replacement, we will fail.
+		 */
+		return false;
+	}
+
+	ck_ht_map_bound_set(map, h, probes);
+
+#ifdef CK_HT_PP
+	ck_pr_store_ptr_unsafe(&candidate->value, (void *)entry->value);
+	ck_pr_fence_store();
+	ck_pr_store_ptr_unsafe(&candidate->key, (void *)entry->key);
+#else
+	CK_HT_TYPE_STORE(&candidate->key_length, entry->key_length);
+	CK_HT_TYPE_STORE(&candidate->hash, entry->hash);
+	ck_pr_store_ptr_unsafe(&candidate->value, (void *)entry->value);
+	ck_pr_fence_store();
+	ck_pr_store_ptr_unsafe(&candidate->key, (void *)entry->key);
+#endif
+
+	CK_HT_TYPE_STORE(&map->n_entries, map->n_entries + 1);
+
+	/* Enforce a load factor of 0.5. */
+	if (map->n_entries * 2 > map->capacity)
+		ck_ht_grow_spmc(table, map->capacity << 1);
+
+	return true;
+}
+
+void
+ck_ht_destroy(struct ck_ht *table)
+{
+
+	ck_ht_map_destroy(table->m, table->map, false);
+	return;
+}
diff --git a/src/ck_ht_hash.h b/src/ck_ht_hash.h
new file mode 100644
index 0000000..cd3d7a5
--- /dev/null
+++ b/src/ck_ht_hash.h
@@ -0,0 +1,269 @@
+/*
+ * Copyright 2012-2015 Samy Al Bahra
+ * Copyright 2011-2014 AppNexus, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef CK_HT_HASH_H
+#define CK_HT_HASH_H
+
+/*
+ * This is the Murmur hash written by Austin Appleby.
+ */
+
+#include <ck_stdint.h>
+#include <ck_string.h>
+
+//-----------------------------------------------------------------------------
+// MurmurHash3 was written by Austin Appleby, and is placed in the public
+// domain. The author hereby disclaims copyright to this source code.
+
+// Note - The x86 and x64 versions do _not_ produce the same results, as the
+// algorithms are optimized for their respective platforms. You can still
+// compile and run any of them on any platform, but your performance with the
+// non-native version will be less than optimal.
+
+//-----------------------------------------------------------------------------
+// Platform-specific functions and macros
+
+// Microsoft Visual Studio
+
+#if defined(_MSC_VER)
+
+#define FORCE_INLINE    __forceinline
+
+#include <stdlib.h>
+
+#define ROTL32(x,y)     _rotl(x,y)
+#define ROTL64(x,y)     _rotl64(x,y)
+
+#define BIG_CONSTANT(x) (x)
+
+// Other compilers
+
+#else   // defined(_MSC_VER)
+
+#define FORCE_INLINE inline __attribute__((always_inline))
+
+static inline uint32_t rotl32 ( uint32_t x, int8_t r )
+{
+  return (x << r) | (x >> (32 - r));
+}
+
+static inline uint64_t rotl64 ( uint64_t x, int8_t r )
+{
+  return (x << r) | (x >> (64 - r));
+}
+
+#define ROTL32(x,y)     rotl32(x,y)
+#define ROTL64(x,y)     rotl64(x,y)
+
+#define BIG_CONSTANT(x) (x##LLU)
+
+#endif // !defined(_MSC_VER)
+
+//-----------------------------------------------------------------------------
+// Block read - if your platform needs to do endian-swapping or can only
+// handle aligned reads, do the conversion here
+
+FORCE_INLINE static uint32_t getblock ( const uint32_t * p, int i )
+{
+  return p[i];
+}
+
+//-----------------------------------------------------------------------------
+// Finalization mix - force all bits of a hash block to avalanche
+
+FORCE_INLINE static uint32_t fmix ( uint32_t h )
+{
+  h ^= h >> 16;
+  h *= 0x85ebca6b;
+  h ^= h >> 13;
+  h *= 0xc2b2ae35;
+  h ^= h >> 16;
+
+  return h;
+}
+
+//-----------------------------------------------------------------------------
+
+static inline void MurmurHash3_x86_32 ( const void * key, int len,
+                          uint32_t seed, uint32_t * out )
+{
+  const uint8_t * data = (const uint8_t*)key;
+  const int nblocks = len / 4;
+  int i;
+
+  uint32_t h1 = seed;
+
+  uint32_t c1 = 0xcc9e2d51;
+  uint32_t c2 = 0x1b873593;
+
+  //----------
+  // body
+
+  const uint32_t * blocks = (const uint32_t *)(const void *)(data + nblocks*4);
+
+  for(i = -nblocks; i; i++)
+  {
+    uint32_t k1 = getblock(blocks,i);
+
+    k1 *= c1;
+    k1 = ROTL32(k1,15);
+    k1 *= c2;
+
+    h1 ^= k1;
+    h1 = ROTL32(h1,13);
+    h1 = h1*5+0xe6546b64;
+  }
+
+  //----------
+  // tail
+
+  const uint8_t * tail = (const uint8_t*)(data + nblocks*4);
+
+  uint32_t k1 = 0;
+
+  switch(len & 3)
+  {
+  case 3: k1 ^= tail[2] << 16;
+  case 2: k1 ^= tail[1] << 8;
+  case 1: k1 ^= tail[0];
+          k1 *= c1; k1 = ROTL32(k1,15); k1 *= c2; h1 ^= k1;
+  };
+
+  //----------
+  // finalization
+
+  h1 ^= len;
+
+  h1 = fmix(h1);
+
+  *(uint32_t *)out = h1;
+}
+
+static inline uint64_t MurmurHash64A ( const void * key, int len, uint64_t seed )
+{
+  const uint64_t m = BIG_CONSTANT(0xc6a4a7935bd1e995);
+  const int r = 47;
+
+  uint64_t h = seed ^ (len * m);
+
+  const uint64_t * data = (const uint64_t *)key;
+  const uint64_t * end = data + (len/8);
+
+  while(data != end)
+  {
+    uint64_t k;
+
+    if (!((uintptr_t)data & 0x7))
+	    k = *data++;
+    else {
+	    memcpy(&k, data, sizeof(k));
+	    data++;
+    }
+
+    k *= m;
+    k ^= k >> r;
+    k *= m;
+
+    h ^= k;
+    h *= m;
+  }
+
+  const unsigned char * data2 = (const unsigned char*)data;
+
+  switch(len & 7)
+  {
+  case 7: h ^= (uint64_t)(data2[6]) << 48;
+  case 6: h ^= (uint64_t)(data2[5]) << 40;
+  case 5: h ^= (uint64_t)(data2[4]) << 32;
+  case 4: h ^= (uint64_t)(data2[3]) << 24;
+  case 3: h ^= (uint64_t)(data2[2]) << 16;
+  case 2: h ^= (uint64_t)(data2[1]) << 8;
+  case 1: h ^= (uint64_t)(data2[0]);
+          h *= m;
+  };
+
+  h ^= h >> r;
+  h *= m;
+  h ^= h >> r;
+
+  return h;
+}
+
+
+// 64-bit hash for 32-bit platforms
+
+static inline uint64_t MurmurHash64B ( const void * key, int len, uint64_t seed )
+{
+  const uint32_t m = 0x5bd1e995;
+  const int r = 24;
+
+  uint32_t h1 = (uint32_t)(seed) ^ len;
+  uint32_t h2 = (uint32_t)(seed >> 32);
+
+  const uint32_t * data = (const uint32_t *)key;
+
+  while(len >= 8)
+  {
+    uint32_t k1 = *data++;
+    k1 *= m; k1 ^= k1 >> r; k1 *= m;
+    h1 *= m; h1 ^= k1;
+    len -= 4;
+
+    uint32_t k2 = *data++;
+    k2 *= m; k2 ^= k2 >> r; k2 *= m;
+    h2 *= m; h2 ^= k2;
+    len -= 4;
+  }
+
+  if(len >= 4)
+  {
+    uint32_t k1 = *data++;
+    k1 *= m; k1 ^= k1 >> r; k1 *= m;
+    h1 *= m; h1 ^= k1;
+    len -= 4;
+  }
+
+  switch(len)
+  {
+  case 3: h2 ^= ((const unsigned char*)data)[2] << 16;
+  case 2: h2 ^= ((const unsigned char*)data)[1] << 8;
+  case 1: h2 ^= ((const unsigned char*)data)[0];
+      h2 *= m;
+  };
+
+  h1 ^= h2 >> 18; h1 *= m;
+  h2 ^= h1 >> 22; h2 *= m;
+  h1 ^= h2 >> 17; h1 *= m;
+  h2 ^= h1 >> 19; h2 *= m;
+
+  uint64_t h = h1;
+
+  h = (h << 32) | h2;
+
+  return h;
+}
+
+#endif /* CK_HT_HASH_H */
diff --git a/src/ck_internal.h b/src/ck_internal.h
new file mode 100644
index 0000000..7aad3d7
--- /dev/null
+++ b/src/ck_internal.h
@@ -0,0 +1,119 @@
+/*
+ * Copyright 2011-2015 Samy Al Bahra.
+ * Copyright 2011 David Joseph.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * Several of these are from: http://graphics.stanford.edu/~seander/bithacks.html
+ */
+
+#define CK_INTERNAL_LOG_0 (0xAAAAAAAA)
+#define CK_INTERNAL_LOG_1 (0xCCCCCCCC)
+#define CK_INTERNAL_LOG_2 (0xF0F0F0F0)
+#define CK_INTERNAL_LOG_3 (0xFF00FF00)
+#define CK_INTERNAL_LOG_4 (0xFFFF0000)
+
+CK_CC_INLINE static uint32_t
+ck_internal_log(uint32_t v)
+{
+        uint32_t r = (v & CK_INTERNAL_LOG_0) != 0;
+
+	r |= ((v & CK_INTERNAL_LOG_4) != 0) << 4;
+	r |= ((v & CK_INTERNAL_LOG_3) != 0) << 3;
+	r |= ((v & CK_INTERNAL_LOG_2) != 0) << 2;
+	r |= ((v & CK_INTERNAL_LOG_1) != 0) << 1;
+        return (r);
+}
+
+CK_CC_INLINE static uint32_t
+ck_internal_power_2(uint32_t v)
+{
+
+        --v;
+        v |= v >> 1;
+        v |= v >> 2;
+        v |= v >> 4;
+        v |= v >> 8;
+        v |= v >> 16;
+        return (++v);
+}
+
+CK_CC_INLINE static unsigned long
+ck_internal_max(unsigned long x, unsigned long y)
+{
+
+	return x ^ ((x ^ y) & -(x < y));
+}
+
+CK_CC_INLINE static uint64_t
+ck_internal_max_64(uint64_t x, uint64_t y)
+{
+
+	return x ^ ((x ^ y) & -(x < y));
+}
+
+CK_CC_INLINE static uint32_t
+ck_internal_max_32(uint32_t x, uint32_t y)
+{
+
+	return x ^ ((x ^ y) & -(x < y));
+}
+
+CK_CC_INLINE static unsigned long
+ck_internal_bsf(unsigned long v)
+{
+#if defined(__GNUC__)
+	return __builtin_ffs(v);
+#else
+	unsigned int i;
+	const unsigned int s = sizeof(unsigned long) * 8 - 1;
+
+	for (i = 0; i < s; i++) {
+		if (v & (1UL << (s - i)))
+			return sizeof(unsigned long) * 8 - i;
+	}
+
+	return 1;
+#endif /* !__GNUC__ */
+}
+
+CK_CC_INLINE static uint64_t
+ck_internal_bsf_64(uint64_t v)
+{
+#if defined(__GNUC__)
+	return __builtin_ffs(v);
+#else
+	unsigned int i;
+	const unsigned int s = sizeof(unsigned long) * 8 - 1;
+
+	for (i = 0; i < s; i++) {
+		if (v & (1ULL << (63U - i)))
+			return i;
+	}
+#endif /* !__GNUC__ */
+
+	return 1;
+}
+
diff --git a/src/ck_rhs.c b/src/ck_rhs.c
new file mode 100644
index 0000000..f6dd2ee
--- /dev/null
+++ b/src/ck_rhs.c
@@ -0,0 +1,1480 @@
+/*
+ * Copyright 2014-2015 Olivier Houchard.
+ * Copyright 2012-2015 Samy Al Bahra.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <ck_cc.h>
+#include <ck_rhs.h>
+#include <ck_limits.h>
+#include <ck_md.h>
+#include <ck_pr.h>
+#include <ck_stdint.h>
+#include <ck_stdbool.h>
+#include <ck_string.h>
+
+#include "ck_internal.h"
+
+#ifndef CK_RHS_PROBE_L1_SHIFT
+#define CK_RHS_PROBE_L1_SHIFT 3ULL
+#endif /* CK_RHS_PROBE_L1_SHIFT */
+
+#define CK_RHS_PROBE_L1 (1 << CK_RHS_PROBE_L1_SHIFT)
+#define CK_RHS_PROBE_L1_MASK (CK_RHS_PROBE_L1 - 1)
+
+#ifndef CK_RHS_PROBE_L1_DEFAULT
+#define CK_RHS_PROBE_L1_DEFAULT CK_MD_CACHELINE
+#endif
+
+#define CK_RHS_VMA_MASK ((uintptr_t)((1ULL << CK_MD_VMA_BITS) - 1))
+#define CK_RHS_VMA(x)	\
+	((void *)((uintptr_t)(x) & CK_RHS_VMA_MASK))
+
+#define CK_RHS_EMPTY     NULL
+#define CK_RHS_G		(1024)
+#define CK_RHS_G_MASK	(CK_RHS_G - 1)
+
+#if defined(CK_F_PR_LOAD_8) && defined(CK_F_PR_STORE_8)
+#define CK_RHS_WORD          uint8_t
+#define CK_RHS_WORD_MAX	    UINT8_MAX
+#define CK_RHS_STORE(x, y)   ck_pr_store_8(x, y)
+#define CK_RHS_LOAD(x)       ck_pr_load_8(x)
+#elif defined(CK_F_PR_LOAD_16) && defined(CK_F_PR_STORE_16)
+#define CK_RHS_WORD          uint16_t
+#define CK_RHS_WORD_MAX	    UINT16_MAX
+#define CK_RHS_STORE(x, y)   ck_pr_store_16(x, y)
+#define CK_RHS_LOAD(x)       ck_pr_load_16(x)
+#elif defined(CK_F_PR_LOAD_32) && defined(CK_F_PR_STORE_32)
+#define CK_RHS_WORD          uint32_t
+#define CK_RHS_WORD_MAX	    UINT32_MAX
+#define CK_RHS_STORE(x, y)   ck_pr_store_32(x, y)
+#define CK_RHS_LOAD(x)       ck_pr_load_32(x)
+#else
+#error "ck_rhs is not supported on your platform."
+#endif
+
+#define CK_RHS_MAX_WANTED	0xffff
+
+enum ck_rhs_probe_behavior {
+	CK_RHS_PROBE = 0,	/* Default behavior. */
+	CK_RHS_PROBE_RH,	/* Short-circuit if RH slot found. */
+	CK_RHS_PROBE_INSERT,	/* Short-circuit on probe bound if tombstone found. */
+
+	CK_RHS_PROBE_ROBIN_HOOD,/* Look for the first slot available for the entry we are about to replace, only used to internally implement Robin Hood */
+	CK_RHS_PROBE_NO_RH,	/* Don't do the RH dance */
+};
+struct ck_rhs_entry_desc {
+	unsigned int probes;
+	unsigned short wanted;
+	CK_RHS_WORD probe_bound;
+	bool in_rh;
+	const void *entry;
+} CK_CC_ALIGN(16);
+
+struct ck_rhs_no_entry_desc {
+	unsigned int probes;
+	unsigned short wanted;
+	CK_RHS_WORD probe_bound;
+	bool in_rh;
+} CK_CC_ALIGN(8);
+
+typedef long ck_rhs_probe_cb_t(struct ck_rhs *hs,
+    struct ck_rhs_map *map,
+    unsigned long *n_probes,
+    long *priority,
+    unsigned long h,
+    const void *key,
+    const void **object,
+    unsigned long probe_limit,
+    enum ck_rhs_probe_behavior behavior);
+
+struct ck_rhs_map {
+	unsigned int generation[CK_RHS_G];
+	unsigned int probe_maximum;
+	unsigned long mask;
+	unsigned long step;
+	unsigned int probe_limit;
+	unsigned long n_entries;
+	unsigned long capacity;
+	unsigned long size;
+	unsigned long max_entries;
+	char offset_mask;
+	union {
+		struct ck_rhs_entry_desc *descs;
+		struct ck_rhs_no_entry {
+			const void **entries;
+			struct ck_rhs_no_entry_desc *descs;
+		} no_entries;
+	} entries;
+	bool read_mostly;
+	ck_rhs_probe_cb_t *probe_func;
+};
+
+static CK_CC_INLINE const void *
+ck_rhs_entry(struct ck_rhs_map *map, long offset)
+{
+
+	if (map->read_mostly)
+		return (map->entries.no_entries.entries[offset]);
+	else
+		return (map->entries.descs[offset].entry);
+}
+
+static CK_CC_INLINE const void **
+ck_rhs_entry_addr(struct ck_rhs_map *map, long offset)
+{
+
+	if (map->read_mostly)
+		return (&map->entries.no_entries.entries[offset]);
+	else
+		return (&map->entries.descs[offset].entry);
+}
+
+static CK_CC_INLINE struct ck_rhs_entry_desc *
+ck_rhs_desc(struct ck_rhs_map *map, long offset)
+{
+
+	if (CK_CC_UNLIKELY(map->read_mostly))
+		return ((struct ck_rhs_entry_desc *)(void *)&map->entries.no_entries.descs[offset]);
+	else
+		return (&map->entries.descs[offset]);
+}
+
+static CK_CC_INLINE void
+ck_rhs_wanted_inc(struct ck_rhs_map *map, long offset)
+{
+
+	if (CK_CC_UNLIKELY(map->read_mostly))
+		map->entries.no_entries.descs[offset].wanted++;
+	else
+		map->entries.descs[offset].wanted++;
+}
+
+static CK_CC_INLINE unsigned int
+ck_rhs_probes(struct ck_rhs_map *map, long offset)
+{
+
+	if (CK_CC_UNLIKELY(map->read_mostly))
+		return (map->entries.no_entries.descs[offset].probes);
+	else
+		return (map->entries.descs[offset].probes);
+}
+
+static CK_CC_INLINE void
+ck_rhs_set_probes(struct ck_rhs_map *map, long offset, unsigned int value)
+{
+
+	if (CK_CC_UNLIKELY(map->read_mostly))
+		map->entries.no_entries.descs[offset].probes = value;
+	else
+		map->entries.descs[offset].probes = value;
+}
+
+static CK_CC_INLINE CK_RHS_WORD
+ck_rhs_probe_bound(struct ck_rhs_map *map, long offset)
+{
+
+	if (CK_CC_UNLIKELY(map->read_mostly))
+		return (map->entries.no_entries.descs[offset].probe_bound);
+	else
+		return (map->entries.descs[offset].probe_bound);
+}
+
+static CK_CC_INLINE CK_RHS_WORD *
+ck_rhs_probe_bound_addr(struct ck_rhs_map *map, long offset)
+{
+
+	if (CK_CC_UNLIKELY(map->read_mostly))
+		return (&map->entries.no_entries.descs[offset].probe_bound);
+	else
+		return (&map->entries.descs[offset].probe_bound);
+}
+
+
+static CK_CC_INLINE bool
+ck_rhs_in_rh(struct ck_rhs_map *map, long offset)
+{
+
+	if (CK_CC_UNLIKELY(map->read_mostly))
+		return (map->entries.no_entries.descs[offset].in_rh);
+	else
+		return (map->entries.descs[offset].in_rh);
+}
+
+static CK_CC_INLINE void
+ck_rhs_set_rh(struct ck_rhs_map *map, long offset)
+{
+
+	if (CK_CC_UNLIKELY(map->read_mostly))
+		map->entries.no_entries.descs[offset].in_rh = true;
+	else
+		map->entries.descs[offset].in_rh = true;
+}
+
+static CK_CC_INLINE void
+ck_rhs_unset_rh(struct ck_rhs_map *map, long offset)
+{
+
+	if (CK_CC_UNLIKELY(map->read_mostly))
+		map->entries.no_entries.descs[offset].in_rh = false;
+	else
+		map->entries.descs[offset].in_rh = false;
+}
+
+
+#define CK_RHS_DEFAULT_LOAD_FACTOR	50
+
+static ck_rhs_probe_cb_t ck_rhs_map_probe;
+static ck_rhs_probe_cb_t ck_rhs_map_probe_rm;
+
+bool
+ck_rhs_set_load_factor(struct ck_rhs *hs, unsigned int load_factor)
+{
+	struct ck_rhs_map *map = hs->map;
+
+	if (load_factor == 0 || load_factor > 100)
+		return false;
+
+	hs->load_factor = load_factor;
+	map->max_entries = (map->capacity * (unsigned long)hs->load_factor) / 100;
+	while (map->n_entries > map->max_entries) {
+		if (ck_rhs_grow(hs, map->capacity << 1) == false)
+			return false;
+		map = hs->map;
+	}
+	return true;
+}
+
+void
+ck_rhs_iterator_init(struct ck_rhs_iterator *iterator)
+{
+
+	iterator->cursor = NULL;
+	iterator->offset = 0;
+	return;
+}
+
+bool
+ck_rhs_next(struct ck_rhs *hs, struct ck_rhs_iterator *i, void **key)
+{
+	struct ck_rhs_map *map = hs->map;
+	void *value;
+
+	if (i->offset >= map->capacity)
+		return false;
+
+	do {
+		value = CK_CC_DECONST_PTR(ck_rhs_entry(map, i->offset));
+		if (value != CK_RHS_EMPTY) {
+#ifdef CK_RHS_PP
+			if (hs->mode & CK_RHS_MODE_OBJECT)
+				value = CK_RHS_VMA(value);
+#endif
+			i->offset++;
+			*key = value;
+			return true;
+		}
+	} while (++i->offset < map->capacity);
+
+	return false;
+}
+
+void
+ck_rhs_stat(struct ck_rhs *hs, struct ck_rhs_stat *st)
+{
+	struct ck_rhs_map *map = hs->map;
+
+	st->n_entries = map->n_entries;
+	st->probe_maximum = map->probe_maximum;
+	return;
+}
+
+unsigned long
+ck_rhs_count(struct ck_rhs *hs)
+{
+
+	return hs->map->n_entries;
+}
+
+static void
+ck_rhs_map_destroy(struct ck_malloc *m, struct ck_rhs_map *map, bool defer)
+{
+
+	m->free(map, map->size, defer);
+	return;
+}
+
+void
+ck_rhs_destroy(struct ck_rhs *hs)
+{
+
+	ck_rhs_map_destroy(hs->m, hs->map, false);
+	return;
+}
+
+static struct ck_rhs_map *
+ck_rhs_map_create(struct ck_rhs *hs, unsigned long entries)
+{
+	struct ck_rhs_map *map;
+	unsigned long size, n_entries, limit;
+
+	n_entries = ck_internal_power_2(entries);
+	if (n_entries < CK_RHS_PROBE_L1)
+		n_entries = CK_RHS_PROBE_L1;
+
+	if (hs->mode & CK_RHS_MODE_READ_MOSTLY)
+		size = sizeof(struct ck_rhs_map) +
+		    (sizeof(void *) * n_entries +
+		     sizeof(struct ck_rhs_no_entry_desc) * n_entries +
+		     2 * CK_MD_CACHELINE - 1);
+	else
+		size = sizeof(struct ck_rhs_map) +
+		    (sizeof(struct ck_rhs_entry_desc) * n_entries +
+		     CK_MD_CACHELINE - 1);
+	map = hs->m->malloc(size);
+	if (map == NULL)
+		return NULL;
+	map->read_mostly = !!(hs->mode & CK_RHS_MODE_READ_MOSTLY);
+
+	map->size = size;
+	/* We should probably use a more intelligent heuristic for default probe length. */
+	limit = ck_internal_max(n_entries >> (CK_RHS_PROBE_L1_SHIFT + 2), CK_RHS_PROBE_L1_DEFAULT);
+	if (limit > UINT_MAX)
+		limit = UINT_MAX;
+
+	map->probe_limit = (unsigned int)limit;
+	map->probe_maximum = 0;
+	map->capacity = n_entries;
+	map->step = ck_internal_bsf(n_entries);
+	map->mask = n_entries - 1;
+	map->n_entries = 0;
+
+	map->max_entries = (map->capacity * (unsigned long)hs->load_factor) / 100;
+	/* Align map allocation to cache line. */
+	if (map->read_mostly) {
+		map->entries.no_entries.entries = (void *)(((uintptr_t)&map[1] +
+		    CK_MD_CACHELINE - 1) & ~(CK_MD_CACHELINE - 1));
+		map->entries.no_entries.descs = (void *)(((uintptr_t)map->entries.no_entries.entries + (sizeof(void *) * n_entries) + CK_MD_CACHELINE - 1) &~ (CK_MD_CACHELINE - 1));
+		memset(map->entries.no_entries.entries, 0,
+		    sizeof(void *) * n_entries);
+		memset(map->entries.no_entries.descs, 0,
+		    sizeof(struct ck_rhs_no_entry_desc) * n_entries);
+		map->offset_mask = (CK_MD_CACHELINE / sizeof(void *)) - 1;
+		map->probe_func = ck_rhs_map_probe_rm;
+
+	} else {
+		map->entries.descs = (void *)(((uintptr_t)&map[1] +
+		    CK_MD_CACHELINE - 1) & ~(CK_MD_CACHELINE - 1));
+		memset(map->entries.descs, 0, sizeof(struct ck_rhs_entry_desc) * n_entries);
+		map->offset_mask = (CK_MD_CACHELINE / sizeof(struct ck_rhs_entry_desc)) - 1;
+		map->probe_func = ck_rhs_map_probe;
+	}
+	memset(map->generation, 0, sizeof map->generation);
+
+	/* Commit entries purge with respect to map publication. */
+	ck_pr_fence_store();
+	return map;
+}
+
+bool
+ck_rhs_reset_size(struct ck_rhs *hs, unsigned long capacity)
+{
+	struct ck_rhs_map *map, *previous;
+
+	previous = hs->map;
+	map = ck_rhs_map_create(hs, capacity);
+	if (map == NULL)
+		return false;
+
+	ck_pr_store_ptr(&hs->map, map);
+	ck_rhs_map_destroy(hs->m, previous, true);
+	return true;
+}
+
+bool
+ck_rhs_reset(struct ck_rhs *hs)
+{
+	struct ck_rhs_map *previous;
+
+	previous = hs->map;
+	return ck_rhs_reset_size(hs, previous->capacity);
+}
+
+static inline unsigned long
+ck_rhs_map_probe_next(struct ck_rhs_map *map,
+    unsigned long offset,
+    unsigned long probes)
+{
+
+	if (probes & map->offset_mask) {
+		offset = (offset &~ map->offset_mask) +
+		    ((offset + 1) & map->offset_mask);
+		return offset;
+	} else
+		return (offset + probes) & map->mask;
+}
+
+static inline unsigned long
+ck_rhs_map_probe_prev(struct ck_rhs_map *map, unsigned long offset,
+    unsigned long probes)
+{
+
+	if (probes & map->offset_mask) {
+		offset = (offset &~ map->offset_mask) + ((offset - 1) &
+		    map->offset_mask);
+		return offset;
+	} else
+		return ((offset - probes) & map->mask);
+}
+
+
+static inline void
+ck_rhs_map_bound_set(struct ck_rhs_map *m,
+    unsigned long h,
+    unsigned long n_probes)
+{
+	unsigned long offset = h & m->mask;
+	struct ck_rhs_entry_desc *desc;
+
+	if (n_probes > m->probe_maximum)
+		ck_pr_store_uint(&m->probe_maximum, n_probes);
+	if (!(m->read_mostly)) {
+		desc = &m->entries.descs[offset];
+
+		if (desc->probe_bound < n_probes) {
+			if (n_probes > CK_RHS_WORD_MAX)
+				n_probes = CK_RHS_WORD_MAX;
+
+			CK_RHS_STORE(&desc->probe_bound, n_probes);
+			ck_pr_fence_store();
+		}
+	}
+
+	return;
+}
+
+static inline unsigned int
+ck_rhs_map_bound_get(struct ck_rhs_map *m, unsigned long h)
+{
+	unsigned long offset = h & m->mask;
+	unsigned int r = CK_RHS_WORD_MAX;
+
+	if (m->read_mostly)
+		r = ck_pr_load_uint(&m->probe_maximum);
+	else {
+		r = CK_RHS_LOAD(&m->entries.descs[offset].probe_bound);
+		if (r == CK_RHS_WORD_MAX)
+			r = ck_pr_load_uint(&m->probe_maximum);
+	}
+	return r;
+}
+
+bool
+ck_rhs_grow(struct ck_rhs *hs,
+    unsigned long capacity)
+{
+	struct ck_rhs_map *map, *update;
+	const void *previous, *prev_saved;
+	unsigned long k, offset, probes;
+
+restart:
+	map = hs->map;
+	if (map->capacity > capacity)
+		return false;
+
+	update = ck_rhs_map_create(hs, capacity);
+	if (update == NULL)
+		return false;
+
+	for (k = 0; k < map->capacity; k++) {
+		unsigned long h;
+
+		prev_saved = previous = ck_rhs_entry(map, k);
+		if (previous == CK_RHS_EMPTY)
+			continue;
+
+#ifdef CK_RHS_PP
+		if (hs->mode & CK_RHS_MODE_OBJECT)
+			previous = CK_RHS_VMA(previous);
+#endif
+
+		h = hs->hf(previous, hs->seed);
+		offset = h & update->mask;
+		probes = 0;
+
+		for (;;) {
+			const void **cursor = ck_rhs_entry_addr(update, offset);
+
+			if (probes++ == update->probe_limit) {
+				/*
+				 * We have hit the probe limit, map needs to be even larger.
+				 */
+				ck_rhs_map_destroy(hs->m, update, false);
+				capacity <<= 1;
+				goto restart;
+			}
+
+			if (CK_CC_LIKELY(*cursor == CK_RHS_EMPTY)) {
+				*cursor = prev_saved;
+				update->n_entries++;
+				ck_rhs_set_probes(update, offset, probes);
+				ck_rhs_map_bound_set(update, h, probes);
+				break;
+			} else if (ck_rhs_probes(update, offset) < probes) {
+				const void *tmp = prev_saved;
+				unsigned int old_probes;
+				prev_saved = previous = *cursor;
+#ifdef CK_RHS_PP
+				if (hs->mode & CK_RHS_MODE_OBJECT)
+					previous = CK_RHS_VMA(previous);
+#endif
+				*cursor = tmp;
+				ck_rhs_map_bound_set(update, h, probes);
+				h = hs->hf(previous, hs->seed);
+				old_probes = ck_rhs_probes(update, offset);
+				ck_rhs_set_probes(update, offset, probes);
+				probes = old_probes - 1;
+				continue;
+			}
+			ck_rhs_wanted_inc(update, offset);
+			offset = ck_rhs_map_probe_next(update, offset,  probes);
+		}
+
+	}
+
+	ck_pr_fence_store();
+	ck_pr_store_ptr(&hs->map, update);
+	ck_rhs_map_destroy(hs->m, map, true);
+	return true;
+}
+
+bool
+ck_rhs_rebuild(struct ck_rhs *hs)
+{
+
+	return ck_rhs_grow(hs, hs->map->capacity);
+}
+
+static long
+ck_rhs_map_probe_rm(struct ck_rhs *hs,
+    struct ck_rhs_map *map,
+    unsigned long *n_probes,
+    long *priority,
+    unsigned long h,
+    const void *key,
+    const void **object,
+    unsigned long probe_limit,
+    enum ck_rhs_probe_behavior behavior)
+{
+	const void *k;
+	const void *compare;
+	long pr = -1;
+	unsigned long offset, probes, opl;
+
+#ifdef CK_RHS_PP
+	/* If we are storing object pointers, then we may leverage pointer packing. */
+	unsigned long hv = 0;
+
+	if (hs->mode & CK_RHS_MODE_OBJECT) {
+		hv = (h >> 25) & CK_RHS_KEY_MASK;
+		compare = CK_RHS_VMA(key);
+	} else {
+		compare = key;
+	}
+#else
+	compare = key;
+#endif
+ 	*object = NULL;
+	if (behavior != CK_RHS_PROBE_ROBIN_HOOD) {
+		probes = 0;
+		offset = h & map->mask;
+	} else {
+		/* Restart from the bucket we were previously in */
+		probes = *n_probes;
+		offset = ck_rhs_map_probe_next(map, *priority,
+		    probes);
+	}
+	opl = probe_limit;
+
+	for (;;) {
+		if (probes++ == probe_limit) {
+			if (probe_limit == opl || pr != -1) {
+				k = CK_RHS_EMPTY;
+				goto leave;
+			}
+			/*
+			 * If no eligible slot has been found yet, continue probe
+			 * sequence with original probe limit.
+			 */
+			probe_limit = opl;
+		}
+		k = ck_pr_load_ptr(&map->entries.no_entries.entries[offset]);
+		if (k == CK_RHS_EMPTY)
+			goto leave;
+
+		if (behavior != CK_RHS_PROBE_NO_RH) {
+			struct ck_rhs_entry_desc *desc = (void *)&map->entries.no_entries.descs[offset];
+
+			if (pr == -1 &&
+			    desc->in_rh == false && desc->probes < probes) {
+				pr = offset;
+				*n_probes = probes;
+
+				if (behavior == CK_RHS_PROBE_RH ||
+				    behavior == CK_RHS_PROBE_ROBIN_HOOD) {
+					k = CK_RHS_EMPTY;
+					goto leave;
+				}
+			}
+		}
+
+		if (behavior != CK_RHS_PROBE_ROBIN_HOOD) {
+#ifdef CK_RHS_PP
+			if (hs->mode & CK_RHS_MODE_OBJECT) {
+				if (((uintptr_t)k >> CK_MD_VMA_BITS) != hv) {
+					offset = ck_rhs_map_probe_next(map, offset, probes);
+					continue;
+				}
+
+				k = CK_RHS_VMA(k);
+			}
+#endif
+
+			if (k == compare)
+				goto leave;
+
+			if (hs->compare == NULL) {
+				offset = ck_rhs_map_probe_next(map, offset, probes);
+				continue;
+			}
+
+			if (hs->compare(k, key) == true)
+				goto leave;
+		}
+		offset = ck_rhs_map_probe_next(map, offset, probes);
+	}
+leave:
+	if (probes > probe_limit) {
+		offset = -1;
+	} else {
+		*object = k;
+	}
+
+	if (pr == -1)
+		*n_probes = probes;
+
+	*priority = pr;
+	return offset;
+}
+
+static long
+ck_rhs_map_probe(struct ck_rhs *hs,
+    struct ck_rhs_map *map,
+    unsigned long *n_probes,
+    long *priority,
+    unsigned long h,
+    const void *key,
+    const void **object,
+    unsigned long probe_limit,
+    enum ck_rhs_probe_behavior behavior)
+{
+	const void *k;
+	const void *compare;
+	long pr = -1;
+	unsigned long offset, probes, opl;
+
+#ifdef CK_RHS_PP
+	/* If we are storing object pointers, then we may leverage pointer packing. */
+	unsigned long hv = 0;
+
+	if (hs->mode & CK_RHS_MODE_OBJECT) {
+		hv = (h >> 25) & CK_RHS_KEY_MASK;
+		compare = CK_RHS_VMA(key);
+	} else {
+		compare = key;
+	}
+#else
+	compare = key;
+#endif
+
+ 	*object = NULL;
+	if (behavior != CK_RHS_PROBE_ROBIN_HOOD) {
+		probes = 0;
+		offset = h & map->mask;
+	} else {
+		/* Restart from the bucket we were previously in */
+		probes = *n_probes;
+		offset = ck_rhs_map_probe_next(map, *priority,
+		    probes);
+	}
+	opl = probe_limit;
+	if (behavior == CK_RHS_PROBE_INSERT)
+		probe_limit = ck_rhs_map_bound_get(map, h);
+
+	for (;;) {
+		if (probes++ == probe_limit) {
+			if (probe_limit == opl || pr != -1) {
+				k = CK_RHS_EMPTY;
+				goto leave;
+			}
+			/*
+			 * If no eligible slot has been found yet, continue probe
+			 * sequence with original probe limit.
+			 */
+			probe_limit = opl;
+		}
+		k = ck_pr_load_ptr(&map->entries.descs[offset].entry);
+		if (k == CK_RHS_EMPTY)
+			goto leave;
+		if ((behavior != CK_RHS_PROBE_NO_RH)) {
+			struct ck_rhs_entry_desc *desc = &map->entries.descs[offset];
+
+			if (pr == -1 &&
+			    desc->in_rh == false && desc->probes < probes) {
+				pr = offset;
+				*n_probes = probes;
+
+				if (behavior == CK_RHS_PROBE_RH ||
+				    behavior == CK_RHS_PROBE_ROBIN_HOOD) {
+					k = CK_RHS_EMPTY;
+					goto leave;
+				}
+			}
+		}
+
+		if (behavior != CK_RHS_PROBE_ROBIN_HOOD) {
+#ifdef CK_RHS_PP
+			if (hs->mode & CK_RHS_MODE_OBJECT) {
+				if (((uintptr_t)k >> CK_MD_VMA_BITS) != hv) {
+					offset = ck_rhs_map_probe_next(map, offset, probes);
+					continue;
+				}
+
+				k = CK_RHS_VMA(k);
+			}
+#endif
+
+			if (k == compare)
+				goto leave;
+
+			if (hs->compare == NULL) {
+				offset = ck_rhs_map_probe_next(map, offset, probes);
+				continue;
+			}
+
+			if (hs->compare(k, key) == true)
+				goto leave;
+		}
+		offset = ck_rhs_map_probe_next(map, offset, probes);
+	}
+leave:
+	if (probes > probe_limit) {
+		offset = -1;
+	} else {
+		*object = k;
+	}
+
+	if (pr == -1)
+		*n_probes = probes;
+
+	*priority = pr;
+	return offset;
+}
+
+static inline const void *
+ck_rhs_marshal(unsigned int mode, const void *key, unsigned long h)
+{
+#ifdef CK_RHS_PP
+	const void *insert;
+
+	if (mode & CK_RHS_MODE_OBJECT) {
+		insert = (void *)((uintptr_t)CK_RHS_VMA(key) | ((h >> 25) << CK_MD_VMA_BITS));
+	} else {
+		insert = key;
+	}
+
+	return insert;
+#else
+	(void)mode;
+	(void)h;
+
+	return key;
+#endif
+}
+
+bool
+ck_rhs_gc(struct ck_rhs *hs)
+{
+	unsigned long i;
+	struct ck_rhs_map *map = hs->map;
+
+	unsigned int max_probes = 0;
+	for (i = 0; i < map->capacity; i++) {
+		if (ck_rhs_probes(map, i) > max_probes)
+			max_probes = ck_rhs_probes(map, i);
+	}
+	map->probe_maximum = max_probes;
+	return true;
+}
+
+static void
+ck_rhs_add_wanted(struct ck_rhs *hs, long end_offset, long old_slot,
+	unsigned long h)
+{
+	struct ck_rhs_map *map = hs->map;
+	long offset;
+	unsigned int probes = 1;
+	bool found_slot = false;
+	struct ck_rhs_entry_desc *desc;
+
+	offset = h & map->mask;
+
+	if (old_slot == -1)
+		found_slot = true;
+	while (offset != end_offset) {
+		if (offset == old_slot)
+			found_slot = true;
+		if (found_slot) {
+			desc = ck_rhs_desc(map, offset);
+			if (desc->wanted < CK_RHS_MAX_WANTED)
+				desc->wanted++;
+		}
+		offset = ck_rhs_map_probe_next(map, offset, probes);
+		probes++;
+	}
+}
+
+static unsigned long
+ck_rhs_remove_wanted(struct ck_rhs *hs, long offset, long limit)
+{
+	struct ck_rhs_map *map = hs->map;
+	int probes = ck_rhs_probes(map, offset);
+	bool do_remove = true;
+	struct ck_rhs_entry_desc *desc;
+
+	while (probes > 1) {
+		probes--;
+		offset = ck_rhs_map_probe_prev(map, offset, probes);
+		if (offset == limit)
+			do_remove = false;
+		if (do_remove) {
+			desc = ck_rhs_desc(map, offset);
+			if (desc->wanted != CK_RHS_MAX_WANTED)
+				desc->wanted--;
+		}
+	}
+	return offset;
+}
+
+static long
+ck_rhs_get_first_offset(struct ck_rhs_map *map, unsigned long offset, unsigned int probes)
+{
+	while (probes > (unsigned long)map->offset_mask + 1) {
+		offset -= ((probes - 1) &~ map->offset_mask);
+		offset &= map->mask;
+		offset = (offset &~ map->offset_mask) +
+		    ((offset - map->offset_mask) & map->offset_mask);
+		probes -= map->offset_mask + 1;
+	}
+	return ((offset &~ map->offset_mask) + ((offset - (probes - 1)) & map->offset_mask));
+}
+
+#define CK_RHS_MAX_RH	512
+
+static int
+ck_rhs_put_robin_hood(struct ck_rhs *hs,
+    long orig_slot, struct ck_rhs_entry_desc *desc)
+{
+	long slot, first;
+	const void *object, *insert;
+	unsigned long n_probes;
+	struct ck_rhs_map *map;
+	unsigned long h = 0;
+	long prev;
+	void *key;
+	long prevs[CK_RHS_MAX_RH];
+	unsigned int prevs_nb = 0;
+	unsigned int i;
+
+	map = hs->map;
+	first = orig_slot;
+	n_probes = desc->probes;
+restart:
+	key = CK_CC_DECONST_PTR(ck_rhs_entry(map, first));
+	insert = key;
+#ifdef CK_RHS_PP
+	if (hs->mode & CK_RHS_MODE_OBJECT)
+	    key = CK_RHS_VMA(key);
+#endif
+	orig_slot = first;
+	ck_rhs_set_rh(map, orig_slot);
+
+	slot = map->probe_func(hs, map, &n_probes, &first, h, key, &object,
+	    map->probe_limit, prevs_nb == CK_RHS_MAX_RH ?
+	    CK_RHS_PROBE_NO_RH : CK_RHS_PROBE_ROBIN_HOOD);
+
+	if (slot == -1 && first == -1) {
+		if (ck_rhs_grow(hs, map->capacity << 1) == false) {
+			desc->in_rh = false;
+
+			for (i = 0; i < prevs_nb; i++)
+				ck_rhs_unset_rh(map, prevs[i]);
+
+			return -1;
+		}
+
+		return 1;
+	}
+
+	if (first != -1) {
+		desc = ck_rhs_desc(map, first);
+		int old_probes = desc->probes;
+
+		desc->probes = n_probes;
+		h = ck_rhs_get_first_offset(map, first, n_probes);
+		ck_rhs_map_bound_set(map, h, n_probes);
+		prev = orig_slot;
+		prevs[prevs_nb++] = prev;
+		n_probes = old_probes;
+		goto restart;
+	} else {
+		/* An empty slot was found. */
+		h =  ck_rhs_get_first_offset(map, slot, n_probes);
+		ck_rhs_map_bound_set(map, h, n_probes);
+		ck_pr_store_ptr(ck_rhs_entry_addr(map, slot), insert);
+		ck_pr_inc_uint(&map->generation[h & CK_RHS_G_MASK]);
+		ck_pr_fence_atomic_store();
+		ck_rhs_set_probes(map, slot, n_probes);
+		desc->in_rh = 0;
+		ck_rhs_add_wanted(hs, slot, orig_slot, h);
+	}
+	while (prevs_nb > 0) {
+		prev = prevs[--prevs_nb];
+		ck_pr_store_ptr(ck_rhs_entry_addr(map, orig_slot),
+		    ck_rhs_entry(map, prev));
+		h = ck_rhs_get_first_offset(map, orig_slot,
+		    desc->probes);
+		ck_rhs_add_wanted(hs, orig_slot, prev, h);
+		ck_pr_inc_uint(&map->generation[h & CK_RHS_G_MASK]);
+		ck_pr_fence_atomic_store();
+		orig_slot = prev;
+		desc->in_rh = false;
+		desc = ck_rhs_desc(map, orig_slot);
+	}
+	return 0;
+}
+
+static void
+ck_rhs_do_backward_shift_delete(struct ck_rhs *hs, long slot)
+{
+	struct ck_rhs_map *map = hs->map;
+	struct ck_rhs_entry_desc *desc, *new_desc = NULL;
+	unsigned long h;
+
+	desc = ck_rhs_desc(map, slot);
+	h = ck_rhs_remove_wanted(hs, slot, -1);
+	while (desc->wanted > 0) {
+		unsigned long offset = 0, tmp_offset;
+		unsigned long wanted_probes = 1;
+		unsigned int probe = 0;
+		unsigned int max_probes;
+
+		/* Find a successor */
+		while (wanted_probes < map->probe_maximum) {
+			probe = wanted_probes;
+			offset = ck_rhs_map_probe_next(map, slot, probe);
+			while (probe < map->probe_maximum) {
+				new_desc = ck_rhs_desc(map, offset);
+				if (new_desc->probes == probe + 1)
+					break;
+				probe++;
+				offset = ck_rhs_map_probe_next(map, offset,
+				    probe);
+			}
+			if (probe < map->probe_maximum)
+				break;
+			wanted_probes++;
+		}
+		if (!(wanted_probes < map->probe_maximum)) {
+			desc->wanted = 0;
+			break;
+		}
+		desc->probes = wanted_probes;
+		h = ck_rhs_remove_wanted(hs, offset, slot);
+		ck_pr_store_ptr(ck_rhs_entry_addr(map, slot),
+		    ck_rhs_entry(map, offset));
+		ck_pr_inc_uint(&map->generation[h & CK_RHS_G_MASK]);
+		ck_pr_fence_atomic_store();
+		if (wanted_probes < CK_RHS_WORD_MAX) {
+			struct ck_rhs_entry_desc *hdesc = ck_rhs_desc(map, h);
+			if (hdesc->wanted == 1)
+				CK_RHS_STORE(&hdesc->probe_bound,
+				    wanted_probes);
+			else if (hdesc->probe_bound == CK_RHS_WORD_MAX ||
+			    hdesc->probe_bound == new_desc->probes) {
+				probe++;
+				if (hdesc->probe_bound == CK_RHS_WORD_MAX)
+					max_probes = map->probe_maximum;
+				else {
+					max_probes = hdesc->probe_bound;
+					max_probes--;
+				}
+				tmp_offset = ck_rhs_map_probe_next(map, offset,
+				    probe);
+				while (probe < max_probes) {
+					if (h == (unsigned long)ck_rhs_get_first_offset(map, tmp_offset, probe))
+						break;
+					probe++;
+					tmp_offset = ck_rhs_map_probe_next(map, tmp_offset, probe);
+				}
+				if (probe == max_probes)
+					CK_RHS_STORE(&hdesc->probe_bound,
+					    wanted_probes);
+			}
+		}
+		if (desc->wanted < CK_RHS_MAX_WANTED)
+			desc->wanted--;
+		slot = offset;
+		desc = new_desc;
+	}
+	ck_pr_store_ptr(ck_rhs_entry_addr(map, slot), CK_RHS_EMPTY);
+	if ((desc->probes - 1) < CK_RHS_WORD_MAX)
+		CK_RHS_STORE(ck_rhs_probe_bound_addr(map, h),
+		    desc->probes - 1);
+	desc->probes = 0;
+}
+
+bool
+ck_rhs_fas(struct ck_rhs *hs,
+    unsigned long h,
+    const void *key,
+    void **previous)
+{
+	long slot, first;
+	const void *object;
+	const void *insert;
+	unsigned long n_probes;
+	struct ck_rhs_map *map = hs->map;
+	struct ck_rhs_entry_desc *desc, *desc2;
+
+	*previous = NULL;
+restart:
+	slot = map->probe_func(hs, map, &n_probes, &first, h, key, &object,
+	    ck_rhs_map_bound_get(map, h), CK_RHS_PROBE);
+
+	/* Replacement semantics presume existence. */
+	if (object == NULL)
+		return false;
+
+	insert = ck_rhs_marshal(hs->mode, key, h);
+
+	if (first != -1) {
+		int ret;
+
+		desc = ck_rhs_desc(map, slot);
+		desc2 = ck_rhs_desc(map, first);
+		desc->in_rh = true;
+		ret = ck_rhs_put_robin_hood(hs, first, desc2);
+		desc->in_rh = false;
+		if (CK_CC_UNLIKELY(ret == 1))
+			goto restart;
+		else if (CK_CC_UNLIKELY(ret != 0))
+			return false;
+		ck_pr_store_ptr(ck_rhs_entry_addr(map, first), insert);
+		ck_pr_inc_uint(&map->generation[h & CK_RHS_G_MASK]);
+		ck_pr_fence_atomic_store();
+		desc2->probes = n_probes;
+		ck_rhs_add_wanted(hs, first, -1, h);
+		ck_rhs_do_backward_shift_delete(hs, slot);
+	} else {
+		ck_pr_store_ptr(ck_rhs_entry_addr(map, slot), insert);
+		ck_rhs_set_probes(map, slot, n_probes);
+	}
+	*previous = CK_CC_DECONST_PTR(object);
+	return true;
+}
+
+/*
+ * An apply function takes two arguments. The first argument is a pointer to a
+ * pre-existing object. The second argument is a pointer to the fifth argument
+ * passed to ck_hs_apply. If a non-NULL pointer is passed to the first argument
+ * and the return value of the apply function is NULL, then the pre-existing
+ * value is deleted. If the return pointer is the same as the one passed to the
+ * apply function then no changes are made to the hash table.  If the first
+ * argument is non-NULL and the return pointer is different than that passed to
+ * the apply function, then the pre-existing value is replaced. For
+ * replacement, it is required that the value itself is identical to the
+ * previous value.
+ */
+bool
+ck_rhs_apply(struct ck_rhs *hs,
+    unsigned long h,
+    const void *key,
+    ck_rhs_apply_fn_t *fn,
+    void *cl)
+{
+	const void *insert;
+	const void  *object, *delta = false;
+	unsigned long n_probes;
+	long slot, first;
+	struct ck_rhs_map *map;
+	bool delta_set = false;
+
+restart:
+	map = hs->map;
+
+	slot = map->probe_func(hs, map, &n_probes, &first, h, key, &object, map->probe_limit, CK_RHS_PROBE_INSERT);
+	if (slot == -1 && first == -1) {
+		if (ck_rhs_grow(hs, map->capacity << 1) == false)
+			return false;
+
+		goto restart;
+	}
+	if (!delta_set) {
+		delta = fn(CK_CC_DECONST_PTR(object), cl);
+		delta_set = true;
+	}
+
+	if (delta == NULL) {
+		/*
+		 * The apply function has requested deletion. If the object doesn't exist,
+		 * then exit early.
+		 */
+		if (CK_CC_UNLIKELY(object == NULL))
+			return true;
+
+		/* Otherwise, delete it. */
+		ck_rhs_do_backward_shift_delete(hs, slot);
+		return true;
+	}
+
+	/* The apply function has not requested hash set modification so exit early. */
+	if (delta == object)
+		return true;
+
+	/* A modification or insertion has been requested. */
+	ck_rhs_map_bound_set(map, h, n_probes);
+
+	insert = ck_rhs_marshal(hs->mode, delta, h);
+	if (first != -1) {
+		/*
+		 * This follows the same semantics as ck_hs_set, please refer to that
+		 * function for documentation.
+		 */
+		struct ck_rhs_entry_desc *desc = NULL, *desc2;
+		if (slot != -1) {
+			desc = ck_rhs_desc(map, slot);
+			desc->in_rh = true;
+		}
+		desc2 = ck_rhs_desc(map, first);
+		int ret = ck_rhs_put_robin_hood(hs, first, desc2);
+		if (slot != -1)
+			desc->in_rh = false;
+
+		if (CK_CC_UNLIKELY(ret == 1))
+			goto restart;
+		if (CK_CC_UNLIKELY(ret == -1))
+			return false;
+		/* If an earlier bucket was found, then store entry there. */
+		ck_pr_store_ptr(ck_rhs_entry_addr(map, first), insert);
+		desc2->probes = n_probes;
+		/*
+		 * If a duplicate key was found, then delete it after
+		 * signaling concurrent probes to restart. Optionally,
+		 * it is possible to install tombstone after grace
+		 * period if we can guarantee earlier position of
+		 * duplicate key.
+		 */
+		ck_rhs_add_wanted(hs, first, -1, h);
+		if (object != NULL) {
+			ck_pr_inc_uint(&map->generation[h & CK_RHS_G_MASK]);
+			ck_pr_fence_atomic_store();
+			ck_rhs_do_backward_shift_delete(hs, slot);
+		}
+	} else {
+		/*
+		 * If we are storing into same slot, then atomic store is sufficient
+		 * for replacement.
+		 */
+		ck_pr_store_ptr(ck_rhs_entry_addr(map, slot), insert);
+		ck_rhs_set_probes(map, slot, n_probes);
+		if (object == NULL)
+			ck_rhs_add_wanted(hs, slot, -1, h);
+	}
+
+	if (object == NULL) {
+		map->n_entries++;
+		if ((map->n_entries ) > map->max_entries)
+			ck_rhs_grow(hs, map->capacity << 1);
+	}
+	return true;
+}
+
+bool
+ck_rhs_set(struct ck_rhs *hs,
+    unsigned long h,
+    const void *key,
+    void **previous)
+{
+	long slot, first;
+	const void *object;
+	const void *insert;
+	unsigned long n_probes;
+	struct ck_rhs_map *map;
+
+	*previous = NULL;
+
+restart:
+	map = hs->map;
+
+	slot = map->probe_func(hs, map, &n_probes, &first, h, key, &object, map->probe_limit, CK_RHS_PROBE_INSERT);
+	if (slot == -1 && first == -1) {
+		if (ck_rhs_grow(hs, map->capacity << 1) == false)
+			return false;
+
+		goto restart;
+	}
+	ck_rhs_map_bound_set(map, h, n_probes);
+	insert = ck_rhs_marshal(hs->mode, key, h);
+
+	if (first != -1) {
+		struct ck_rhs_entry_desc *desc = NULL, *desc2;
+		if (slot != -1) {
+			desc = ck_rhs_desc(map, slot);
+			desc->in_rh = true;
+		}
+		desc2 = ck_rhs_desc(map, first);
+		int ret = ck_rhs_put_robin_hood(hs, first, desc2);
+		if (slot != -1)
+			desc->in_rh = false;
+
+		if (CK_CC_UNLIKELY(ret == 1))
+			goto restart;
+		if (CK_CC_UNLIKELY(ret == -1))
+			return false;
+		/* If an earlier bucket was found, then store entry there. */
+		ck_pr_store_ptr(ck_rhs_entry_addr(map, first), insert);
+		desc2->probes = n_probes;
+		/*
+		 * If a duplicate key was found, then delete it after
+		 * signaling concurrent probes to restart. Optionally,
+		 * it is possible to install tombstone after grace
+		 * period if we can guarantee earlier position of
+		 * duplicate key.
+		 */
+		ck_rhs_add_wanted(hs, first, -1, h);
+		if (object != NULL) {
+			ck_pr_inc_uint(&map->generation[h & CK_RHS_G_MASK]);
+			ck_pr_fence_atomic_store();
+			ck_rhs_do_backward_shift_delete(hs, slot);
+		}
+
+	} else {
+		/*
+		 * If we are storing into same slot, then atomic store is sufficient
+		 * for replacement.
+		 */
+		ck_pr_store_ptr(ck_rhs_entry_addr(map, slot), insert);
+		ck_rhs_set_probes(map, slot, n_probes);
+		if (object == NULL)
+			ck_rhs_add_wanted(hs, slot, -1, h);
+	}
+
+	if (object == NULL) {
+		map->n_entries++;
+		if ((map->n_entries ) > map->max_entries)
+			ck_rhs_grow(hs, map->capacity << 1);
+	}
+
+	*previous = CK_CC_DECONST_PTR(object);
+	return true;
+}
+
+static bool
+ck_rhs_put_internal(struct ck_rhs *hs,
+    unsigned long h,
+    const void *key,
+    enum ck_rhs_probe_behavior behavior)
+{
+	long slot, first;
+	const void *object;
+	const void *insert;
+	unsigned long n_probes;
+	struct ck_rhs_map *map;
+
+restart:
+	map = hs->map;
+
+	slot = map->probe_func(hs, map, &n_probes, &first, h, key, &object,
+	    map->probe_limit, behavior);
+
+	if (slot == -1 && first == -1) {
+		if (ck_rhs_grow(hs, map->capacity << 1) == false)
+			return false;
+
+		goto restart;
+	}
+
+	/* Fail operation if a match was found. */
+	if (object != NULL)
+		return false;
+
+	ck_rhs_map_bound_set(map, h, n_probes);
+	insert = ck_rhs_marshal(hs->mode, key, h);
+
+	if (first != -1) {
+		struct ck_rhs_entry_desc *desc = ck_rhs_desc(map, first);
+		int ret = ck_rhs_put_robin_hood(hs, first, desc);
+		if (CK_CC_UNLIKELY(ret == 1))
+			return ck_rhs_put_internal(hs, h, key, behavior);
+		else if (CK_CC_UNLIKELY(ret == -1))
+			return false;
+		/* Insert key into first bucket in probe sequence. */
+		ck_pr_store_ptr(ck_rhs_entry_addr(map, first), insert);
+		desc->probes = n_probes;
+		ck_rhs_add_wanted(hs, first, -1, h);
+	} else {
+		/* An empty slot was found. */
+		ck_pr_store_ptr(ck_rhs_entry_addr(map, slot), insert);
+		ck_rhs_set_probes(map, slot, n_probes);
+		ck_rhs_add_wanted(hs, slot, -1, h);
+	}
+
+	map->n_entries++;
+	if ((map->n_entries ) > map->max_entries)
+		ck_rhs_grow(hs, map->capacity << 1);
+	return true;
+}
+
+bool
+ck_rhs_put(struct ck_rhs *hs,
+    unsigned long h,
+    const void *key)
+{
+
+	return ck_rhs_put_internal(hs, h, key, CK_RHS_PROBE_INSERT);
+}
+
+bool
+ck_rhs_put_unique(struct ck_rhs *hs,
+    unsigned long h,
+    const void *key)
+{
+
+	return ck_rhs_put_internal(hs, h, key, CK_RHS_PROBE_RH);
+}
+
+void *
+ck_rhs_get(struct ck_rhs *hs,
+    unsigned long h,
+    const void *key)
+{
+	long first;
+	const void *object;
+	struct ck_rhs_map *map;
+	unsigned long n_probes;
+	unsigned int g, g_p, probe;
+	unsigned int *generation;
+
+	do {
+		map = ck_pr_load_ptr(&hs->map);
+		generation = &map->generation[h & CK_RHS_G_MASK];
+		g = ck_pr_load_uint(generation);
+		probe  = ck_rhs_map_bound_get(map, h);
+		ck_pr_fence_load();
+
+		first = -1;
+		map->probe_func(hs, map, &n_probes, &first, h, key, &object, probe, CK_RHS_PROBE_NO_RH);
+
+		ck_pr_fence_load();
+		g_p = ck_pr_load_uint(generation);
+	} while (g != g_p);
+
+	return CK_CC_DECONST_PTR(object);
+}
+
+void *
+ck_rhs_remove(struct ck_rhs *hs,
+    unsigned long h,
+    const void *key)
+{
+	long slot, first;
+	const void *object;
+	struct ck_rhs_map *map = hs->map;
+	unsigned long n_probes;
+
+	slot = map->probe_func(hs, map, &n_probes, &first, h, key, &object,
+	    ck_rhs_map_bound_get(map, h), CK_RHS_PROBE_NO_RH);
+	if (object == NULL)
+		return NULL;
+
+	map->n_entries--;
+	ck_rhs_do_backward_shift_delete(hs, slot);
+	return CK_CC_DECONST_PTR(object);
+}
+
+bool
+ck_rhs_move(struct ck_rhs *hs,
+    struct ck_rhs *source,
+    ck_rhs_hash_cb_t *hf,
+    ck_rhs_compare_cb_t *compare,
+    struct ck_malloc *m)
+{
+
+	if (m == NULL || m->malloc == NULL || m->free == NULL || hf == NULL)
+		return false;
+
+	hs->mode = source->mode;
+	hs->seed = source->seed;
+	hs->map = source->map;
+	hs->load_factor = source->load_factor;
+	hs->m = m;
+	hs->hf = hf;
+	hs->compare = compare;
+	return true;
+}
+
+bool
+ck_rhs_init(struct ck_rhs *hs,
+    unsigned int mode,
+    ck_rhs_hash_cb_t *hf,
+    ck_rhs_compare_cb_t *compare,
+    struct ck_malloc *m,
+    unsigned long n_entries,
+    unsigned long seed)
+{
+
+	if (m == NULL || m->malloc == NULL || m->free == NULL || hf == NULL)
+		return false;
+
+	hs->m = m;
+	hs->mode = mode;
+	hs->seed = seed;
+	hs->hf = hf;
+	hs->compare = compare;
+	hs->load_factor = CK_RHS_DEFAULT_LOAD_FACTOR;
+
+	hs->map = ck_rhs_map_create(hs, n_entries);
+	return hs->map != NULL;
+}