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/* Copyright (c) 2015-2018 Dovecot authors, see the included COPYING file */
#include "lib.h"
#include "stats-dist.h"
#include "sort.h"
/* In order to have a vaguely accurate 95th percentile, you need way
more than 20 in your subsample. */
#define TIMING_DEFAULT_SUBSAMPLING_BUFFER (20*24) /* 20*24 fits in a page */
struct stats_dist {
unsigned int sample_count;
unsigned int count;
bool sorted;
uint64_t min;
uint64_t max;
uint64_t sum;
uint64_t samples[];
};
struct stats_dist *stats_dist_init(void)
{
return stats_dist_init_with_size(TIMING_DEFAULT_SUBSAMPLING_BUFFER);
}
struct stats_dist *stats_dist_init_with_size(unsigned int sample_count)
{
i_assert(sample_count > 0);
struct stats_dist *stats =
i_malloc(sizeof(struct stats_dist) +
sizeof(uint64_t) * sample_count);
stats->sample_count = sample_count;
return stats;
}
void stats_dist_deinit(struct stats_dist **_stats)
{
i_free_and_null(*_stats);
}
void stats_dist_reset(struct stats_dist *stats)
{
unsigned int sample_count = stats->sample_count;
i_zero(stats);
stats->sample_count = sample_count;
}
void stats_dist_add(struct stats_dist *stats, uint64_t value)
{
if (stats->count < stats->sample_count) {
stats->samples[stats->count] = value;
if (stats->count == 0)
stats->min = stats->max = value;
} else {
unsigned int idx = i_rand_limit(stats->count);
if (idx < stats->sample_count)
stats->samples[idx] = value;
}
stats->count++;
stats->sum += value;
if (stats->max < value)
stats->max = value;
if (stats->min > value)
stats->min = value;
stats->sorted = FALSE;
}
unsigned int stats_dist_get_count(const struct stats_dist *stats)
{
return stats->count;
}
uint64_t stats_dist_get_sum(const struct stats_dist *stats)
{
return stats->sum;
}
uint64_t stats_dist_get_min(const struct stats_dist *stats)
{
return stats->min;
}
uint64_t stats_dist_get_max(const struct stats_dist *stats)
{
return stats->max;
}
double stats_dist_get_avg(const struct stats_dist *stats)
{
if (stats->count == 0)
return 0;
return (double)stats->sum / stats->count;
}
static void stats_dist_ensure_sorted(struct stats_dist *stats)
{
if (stats->sorted)
return;
unsigned int count = (stats->count < stats->sample_count)
? stats->count
: stats->sample_count;
i_qsort(stats->samples, count, sizeof(*stats->samples),
uint64_cmp);
stats->sorted = TRUE;
}
uint64_t stats_dist_get_median(struct stats_dist *stats)
{
if (stats->count == 0)
return 0;
/* cast-away const - reading requires sorting */
stats_dist_ensure_sorted(stats);
unsigned int count = (stats->count < stats->sample_count)
? stats->count
: stats->sample_count;
unsigned int idx1 = (count-1)/2, idx2 = count/2;
return (stats->samples[idx1] + stats->samples[idx2]) / 2;
}
double stats_dist_get_variance(const struct stats_dist *stats)
{
double sum = 0;
if (stats->count == 0)
return 0;
double avg = stats_dist_get_avg(stats);
double count = (stats->count < stats->sample_count)
? stats->count
: stats->sample_count;
for(unsigned int i = 0; i < count; i++) {
sum += (stats->samples[i] - avg)*(stats->samples[i] - avg);
}
return sum / count;
}
/* This is independent of the stats framework, useful for any selection task */
static unsigned int stats_dist_get_index(unsigned int range, double fraction)
{
/* With out of range fractions, we can give the caller what
they probably want rather than just crashing. */
if (fraction >= 1.)
return range - 1;
if (fraction <= 0.)
return 0;
double idx_float = range * fraction;
unsigned int idx = idx_float; /* C defaults to rounding down */
idx_float -= idx;
/* Exact boundaries belong to the open range below them.
As FP isn't exact, and ratios may be specified inexactly,
include a small amount of fuzz around the exact boundary. */
if (idx_float < 1e-8*range)
idx--;
return idx;
}
uint64_t stats_dist_get_percentile(struct stats_dist *stats, double fraction)
{
if (stats->count == 0)
return 0;
stats_dist_ensure_sorted(stats);
unsigned int count = (stats->count < stats->sample_count)
? stats->count
: stats->sample_count;
unsigned int idx = stats_dist_get_index(count, fraction);
return stats->samples[idx];
}
const uint64_t *stats_dist_get_samples(const struct stats_dist *stats,
unsigned int *count_r)
{
*count_r = (stats->count < stats->sample_count)
? stats->count
: stats->sample_count;
return stats->samples;
}
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