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203c3841fc
Because the structure started small, I initialized every member directly, but that means that the new fields added weren't properly initialized (sigh!). Zero the whole thing first then. Also, the punishment for introducing a bug should be to write the corresponding unit test. It's not a perfect one, but I'll take it. Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
100 lines
2.7 KiB
C
100 lines
2.7 KiB
C
/*
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* Copyright © 2015 Intel Corporation
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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* IN THE SOFTWARE.
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*
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*/
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#include <math.h>
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#include <string.h>
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#include "igt_core.h"
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#include "igt_stats.h"
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void igt_stats_init(igt_stats_t *stats, unsigned int capacity)
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{
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memset(stats, 0, sizeof(*stats));
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stats->values = calloc(capacity, sizeof(*stats->values));
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igt_assert(stats->values);
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stats->capacity = capacity;
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}
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void igt_stats_fini(igt_stats_t *stats)
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{
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free(stats->values);
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}
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void igt_stats_push(igt_stats_t *stats, uint64_t value)
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{
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igt_assert(stats->n_values < stats->capacity);
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stats->values[stats->n_values++] = value;
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stats->mean_variance_valid = false;
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}
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/*
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* Algorithm popularised by Knuth in:
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*
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* The Art of Computer Programming, volume 2: Seminumerical Algorithms,
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* 3rd edn., p. 232. Boston: Addison-Wesley
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*
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* Source: https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance
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*/
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static void igt_stats_knuth_mean_variance(igt_stats_t *stats)
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{
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double mean = 0., m2 = 0.;
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unsigned int i;
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if (stats->mean_variance_valid)
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return;
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for (i = 0; i < stats->n_values; i++) {
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double delta = stats->values[i] - mean;
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mean += delta / (i + 1);
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m2 += delta * (stats->values[i] - mean);
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}
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stats->mean = mean;
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stats->variance = m2 / stats->n_values;
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stats->mean_variance_valid = true;
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}
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double igt_stats_get_mean(igt_stats_t *stats)
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{
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igt_stats_knuth_mean_variance(stats);
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return stats->mean;
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}
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double igt_stats_get_variance(igt_stats_t *stats)
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{
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igt_stats_knuth_mean_variance(stats);
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return stats->variance;
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}
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double igt_stats_get_std_deviation(igt_stats_t *stats)
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{
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igt_stats_knuth_mean_variance(stats);
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return sqrt(stats->variance);
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}
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