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+/* Copyright (c) the JPEG XL Project Authors. All rights reserved.
+ *
+ * Use of this source code is governed by a BSD-style
+ * license that can be found in the LICENSE file.
+ */
+
+/** @addtogroup libjxl_threads
+ * @{
+ * @file thread_parallel_runner.h
+ * @brief implementation using std::thread of a ::JxlParallelRunner.
+ */
+
+/** Implementation of JxlParallelRunner than can be used to enable
+ * multithreading when using the JPEG XL library. This uses std::thread
+ * internally and related synchronization functions. The number of threads
+ * created is fixed at construction time and the threads are re-used for every
+ * ThreadParallelRunner::Runner call. Only one concurrent
+ * JxlThreadParallelRunner call per instance is allowed at a time.
+ *
+ * This is a scalable, lower-overhead thread pool runner, especially suitable
+ * for data-parallel computations in the fork-join model, where clients need to
+ * know when all tasks have completed.
+ *
+ * This thread pool can efficiently load-balance millions of tasks using an
+ * atomic counter, thus avoiding per-task virtual or system calls. With 48
+ * hyperthreads and 1M tasks that add to an atomic counter, overall runtime is
+ * 10-20x higher when using std::async, and ~200x for a queue-based thread
+ */
+
+#ifndef JXL_THREAD_PARALLEL_RUNNER_H_
+#define JXL_THREAD_PARALLEL_RUNNER_H_
+
+#include <jxl/jxl_threads_export.h>
+#include <jxl/memory_manager.h>
+#include <jxl/parallel_runner.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+/** Parallel runner internally using std::thread. Use as JxlParallelRunner.
+ */
+JXL_THREADS_EXPORT JxlParallelRetCode JxlThreadParallelRunner(
+    void* runner_opaque, void* jpegxl_opaque, JxlParallelRunInit init,
+    JxlParallelRunFunction func, uint32_t start_range, uint32_t end_range);
+
+/** Creates the runner for JxlThreadParallelRunner. Use as the opaque
+ * runner.
+ */
+JXL_THREADS_EXPORT void* JxlThreadParallelRunnerCreate(
+    const JxlMemoryManager* memory_manager, size_t num_worker_threads);
+
+/** Destroys the runner created by JxlThreadParallelRunnerCreate.
+ */
+JXL_THREADS_EXPORT void JxlThreadParallelRunnerDestroy(void* runner_opaque);
+
+/** Returns a default num_worker_threads value for
+ * JxlThreadParallelRunnerCreate.
+ */
+JXL_THREADS_EXPORT size_t JxlThreadParallelRunnerDefaultNumWorkerThreads();
+
+#if defined(__cplusplus) || defined(c_plusplus)
+}
+#endif
+
+#endif /* JXL_THREAD_PARALLEL_RUNNER_H_ */
+
+/** @}*/