Adding upstream version 4.0.upstream/4.0upstream

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

1 files changed, 452 insertions, 0 deletions

diff --git a/samplefilt.c b/samplefilt.c
new file mode 100644
index 0000000..f350e40
--- /dev/null
+++ b/samplefilt.c
@@ -0,0 +1,452 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2009-2011, 2014, 2016, 2018
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Routines implementing a median sample filter.
+
+  */
+
+#include "config.h"
+
+#include "local.h"
+#include "logging.h"
+#include "memory.h"
+#include "regress.h"
+#include "samplefilt.h"
+#include "util.h"
+
+#define MIN_SAMPLES 1
+#define MAX_SAMPLES 256
+
+struct SPF_Instance_Record {
+  int min_samples;
+  int max_samples;
+  int index;
+  int used;
+  int last;
+  int avg_var_n;
+  double avg_var;
+  double max_var;
+  double combine_ratio;
+  NTP_Sample *samples;
+  int *selected;
+  double *x_data;
+  double *y_data;
+  double *w_data;
+};
+
+/* ================================================== */
+
+SPF_Instance
+SPF_CreateInstance(int min_samples, int max_samples, double max_dispersion, double combine_ratio)
+{
+  SPF_Instance filter;
+
+  filter = MallocNew(struct SPF_Instance_Record);
+
+  min_samples = CLAMP(MIN_SAMPLES, min_samples, MAX_SAMPLES);
+  max_samples = CLAMP(MIN_SAMPLES, max_samples, MAX_SAMPLES);
+  max_samples = MAX(min_samples, max_samples);
+  combine_ratio = CLAMP(0.0, combine_ratio, 1.0);
+
+  filter->min_samples = min_samples;
+  filter->max_samples = max_samples;
+  filter->index = -1;
+  filter->used = 0;
+  filter->last = -1;
+  /* Set the first estimate to the system precision */
+  filter->avg_var_n = 0;
+  filter->avg_var = SQUARE(LCL_GetSysPrecisionAsQuantum());
+  filter->max_var = SQUARE(max_dispersion);
+  filter->combine_ratio = combine_ratio;
+  filter->samples = MallocArray(NTP_Sample, filter->max_samples);
+  filter->selected = MallocArray(int, filter->max_samples);
+  filter->x_data = MallocArray(double, filter->max_samples);
+  filter->y_data = MallocArray(double, filter->max_samples);
+  filter->w_data = MallocArray(double, filter->max_samples);
+
+  return filter;
+}
+
+/* ================================================== */
+
+void
+SPF_DestroyInstance(SPF_Instance filter)
+{
+  Free(filter->samples);
+  Free(filter->selected);
+  Free(filter->x_data);
+  Free(filter->y_data);
+  Free(filter->w_data);
+  Free(filter);
+}
+
+/* ================================================== */
+
+/* Check that samples times are strictly increasing */
+
+static int
+check_sample(SPF_Instance filter, NTP_Sample *sample)
+{
+  if (filter->used <= 0)
+    return 1;
+
+  if (UTI_CompareTimespecs(&filter->samples[filter->last].time, &sample->time) >= 0) {
+    DEBUG_LOG("filter non-increasing sample time %s", UTI_TimespecToString(&sample->time));
+    return 0;
+  }
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+SPF_AccumulateSample(SPF_Instance filter, NTP_Sample *sample)
+{
+  if (!check_sample(filter, sample))
+      return 0;
+
+  filter->index++;
+  filter->index %= filter->max_samples;
+  filter->last = filter->index;
+  if (filter->used < filter->max_samples)
+    filter->used++;
+
+  filter->samples[filter->index] = *sample;
+
+  DEBUG_LOG("filter sample %d t=%s offset=%.9f peer_disp=%.9f",
+            filter->index, UTI_TimespecToString(&sample->time),
+            sample->offset, sample->peer_dispersion);
+  return 1;
+}
+
+/* ================================================== */
+
+int
+SPF_GetLastSample(SPF_Instance filter, NTP_Sample *sample)
+{
+  if (filter->last < 0)
+    return 0;
+
+  *sample = filter->samples[filter->last];
+  return 1;
+}
+
+/* ================================================== */
+
+int
+SPF_GetNumberOfSamples(SPF_Instance filter)
+{
+  return filter->used;
+}
+
+/* ================================================== */
+
+double
+SPF_GetAvgSampleDispersion(SPF_Instance filter)
+{
+  return sqrt(filter->avg_var);
+}
+
+/* ================================================== */
+
+void
+SPF_DropSamples(SPF_Instance filter)
+{
+  filter->index = -1;
+  filter->used = 0;
+}
+
+/* ================================================== */
+
+static const NTP_Sample *tmp_sort_samples;
+
+static int
+compare_samples(const void *a, const void *b)
+{
+  const NTP_Sample *s1, *s2;
+
+  s1 = &tmp_sort_samples[*(int *)a];
+  s2 = &tmp_sort_samples[*(int *)b];
+
+  if (s1->offset < s2->offset)
+    return -1;
+  else if (s1->offset > s2->offset)
+    return 1;
+  return 0;
+}
+
+/* ================================================== */
+
+static int
+select_samples(SPF_Instance filter)
+{
+  int i, j, k, o, from, to, *selected;
+  double min_dispersion;
+
+  if (filter->used < filter->min_samples)
+    return 0;
+
+  selected = filter->selected;
+
+  /* With 4 or more samples, select those that have peer dispersion smaller
+     than 1.5x of the minimum dispersion */
+  if (filter->used > 4) {
+    for (i = 1, min_dispersion = filter->samples[0].peer_dispersion; i < filter->used; i++) {
+      if (min_dispersion > filter->samples[i].peer_dispersion)
+        min_dispersion = filter->samples[i].peer_dispersion;
+    }
+
+    for (i = j = 0; i < filter->used; i++) {
+      if (filter->samples[i].peer_dispersion <= 1.5 * min_dispersion)
+        selected[j++] = i;
+    }
+  } else {
+    j = 0;
+  }
+
+  if (j < 4) {
+    /* Select all samples */
+
+    for (j = 0; j < filter->used; j++)
+      selected[j] = j;
+  }
+
+  /* And sort their indices by offset */
+  tmp_sort_samples = filter->samples;
+  qsort(selected, j, sizeof (int), compare_samples);
+
+  /* Select samples closest to the median */
+  if (j > 2) {
+    from = j * (1.0 - filter->combine_ratio) / 2.0;
+    from = CLAMP(1, from, (j - 1) / 2);
+  } else {
+    from = 0;
+  }
+
+  to = j - from;
+
+  /* Mark unused samples and sort the rest by their time */
+
+  o = filter->used - filter->index - 1;
+
+  for (i = 0; i < from; i++)
+    selected[i] = -1;
+  for (; i < to; i++)
+    selected[i] = (selected[i] + o) % filter->used;
+  for (; i < filter->used; i++)
+    selected[i] = -1;
+
+  for (i = from; i < to; i++) {
+    j = selected[i];
+    selected[i] = -1;
+    while (j != -1 && selected[j] != j) {
+      k = selected[j];
+      selected[j] = j;
+      j = k;
+    }
+  }
+
+  for (i = j = 0; i < filter->used; i++) {
+    if (selected[i] != -1)
+      selected[j++] = (selected[i] + filter->used - o) % filter->used;
+  }
+
+  assert(j > 0 && j <= filter->max_samples);
+
+  return j;
+}
+
+/* ================================================== */
+
+static int
+combine_selected_samples(SPF_Instance filter, int n, NTP_Sample *result)
+{
+  double mean_peer_dispersion, mean_root_dispersion, mean_peer_delay, mean_root_delay;
+  double mean_x, mean_y, disp, var, prev_avg_var;
+  NTP_Sample *sample, *last_sample;
+  int i, dof;
+
+  last_sample = &filter->samples[filter->selected[n - 1]];
+
+  /* Prepare data */
+  for (i = 0; i < n; i++) {
+    sample = &filter->samples[filter->selected[i]];
+
+    filter->x_data[i] = UTI_DiffTimespecsToDouble(&sample->time, &last_sample->time);
+    filter->y_data[i] = sample->offset;
+    filter->w_data[i] = sample->peer_dispersion;
+  }
+
+  /* Calculate mean offset and interval since the last sample */
+  for (i = 0, mean_x = mean_y = 0.0; i < n; i++) {
+    mean_x += filter->x_data[i];
+    mean_y += filter->y_data[i];
+  }
+  mean_x /= n;
+  mean_y /= n;
+
+  if (n >= 4) {
+    double b0, b1, s2, sb0, sb1;
+
+    /* Set y axis to the mean sample time */
+    for (i = 0; i < n; i++)
+      filter->x_data[i] -= mean_x;
+
+    /* Make a linear fit and use the estimated standard deviation of the
+       intercept as dispersion */
+    RGR_WeightedRegression(filter->x_data, filter->y_data, filter->w_data, n,
+                           &b0, &b1, &s2, &sb0, &sb1);
+    var = s2;
+    disp = sb0;
+    dof = n - 2;
+  } else if (n >= 2) {
+    for (i = 0, disp = 0.0; i < n; i++)
+      disp += (filter->y_data[i] - mean_y) * (filter->y_data[i] - mean_y);
+    var = disp / (n - 1);
+    disp = sqrt(var);
+    dof = n - 1;
+  } else {
+    var = filter->avg_var;
+    disp = sqrt(var);
+    dof = 1;
+  }
+
+  /* Avoid working with zero dispersion */
+  if (var < 1e-20) {
+    var = 1e-20;
+    disp = sqrt(var);
+  }
+
+  /* Drop the sample if the variance is larger than the maximum */
+  if (filter->max_var > 0.0 && var > filter->max_var) {
+    DEBUG_LOG("filter dispersion too large disp=%.9f max=%.9f",
+              sqrt(var), sqrt(filter->max_var));
+    return 0;
+  }
+
+  prev_avg_var = filter->avg_var;
+
+  /* Update the exponential moving average of the variance */
+  if (filter->avg_var_n > 50) {
+    filter->avg_var += dof / (dof + 50.0) * (var - filter->avg_var);
+  } else {
+    filter->avg_var = (filter->avg_var * filter->avg_var_n + var * dof) /
+      (dof + filter->avg_var_n);
+    if (filter->avg_var_n == 0)
+      prev_avg_var = filter->avg_var;
+    filter->avg_var_n += dof;
+  }
+
+  /* Use the long-term average of variance instead of the estimated value
+     unless it is significantly smaller in order to reduce the noise in
+     sourcestats weights */
+  if (var * dof / RGR_GetChi2Coef(dof) < prev_avg_var)
+    disp = sqrt(filter->avg_var) * disp / sqrt(var);
+
+  mean_peer_dispersion = mean_root_dispersion = mean_peer_delay = mean_root_delay = 0.0;
+
+  for (i = 0; i < n; i++) {
+    sample = &filter->samples[filter->selected[i]];
+
+    mean_peer_dispersion += sample->peer_dispersion;
+    mean_root_dispersion += sample->root_dispersion;
+    mean_peer_delay += sample->peer_delay;
+    mean_root_delay += sample->root_delay;
+  }
+
+  mean_peer_dispersion /= n;
+  mean_root_dispersion /= n;
+  mean_peer_delay /= n;
+  mean_root_delay /= n;
+
+  UTI_AddDoubleToTimespec(&last_sample->time, mean_x, &result->time);
+  result->offset = mean_y;
+  result->peer_dispersion = MAX(disp, mean_peer_dispersion);
+  result->root_dispersion = MAX(disp, mean_root_dispersion);
+  result->peer_delay = mean_peer_delay;
+  result->root_delay = mean_root_delay;
+  result->stratum = last_sample->stratum;
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+SPF_GetFilteredSample(SPF_Instance filter, NTP_Sample *sample)
+{
+  int n;
+
+  n = select_samples(filter);
+
+  if (n < 1)
+    return 0;
+
+  if (!combine_selected_samples(filter, n, sample))
+    return 0;
+
+  SPF_DropSamples(filter);
+
+  return 1;
+}
+
+/* ================================================== */
+
+void
+SPF_SlewSamples(SPF_Instance filter, struct timespec *when, double dfreq, double doffset)
+{
+  int i, first, last;
+  double delta_time;
+
+  if (filter->last < 0)
+    return;
+
+  /* Always slew the last sample as it may be returned even if no new
+     samples were accumulated */
+  if (filter->used > 0) {
+    first = 0;
+    last = filter->used - 1;
+  } else {
+    first = last = filter->last;
+  }
+
+  for (i = first; i <= last; i++) {
+    UTI_AdjustTimespec(&filter->samples[i].time, when, &filter->samples[i].time,
+                       &delta_time, dfreq, doffset);
+    filter->samples[i].offset -= delta_time;
+  }
+}
+
+/* ================================================== */
+
+void
+SPF_AddDispersion(SPF_Instance filter, double dispersion)
+{
+  int i;
+
+  for (i = 0; i < filter->used; i++) {
+    filter->samples[i].peer_dispersion += dispersion;
+    filter->samples[i].root_dispersion += dispersion;
+  }
+}