1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
|
/*
* Copyright © 2015 Intel Corporation
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*
*/
#include "igt_core.h"
#include "igt_stats.h"
void igt_stats_init(igt_stats_t *stats, unsigned int capacity)
{
stats->values = calloc(capacity, sizeof(*stats->values));
igt_assert(stats->values);
stats->capacity = capacity;
stats->n_values = 0;
}
void igt_stats_fini(igt_stats_t *stats)
{
free(stats->values);
}
void igt_stats_push(igt_stats_t *stats, uint64_t value)
{
igt_assert(stats->n_values < stats->capacity);
stats->values[stats->n_values++] = value;
stats->mean_variance_valid = false;
}
/*
* Algorithm popularised by Knuth in:
*
* The Art of Computer Programming, volume 2: Seminumerical Algorithms,
* 3rd edn., p. 232. Boston: Addison-Wesley
*
* Source: https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance
*/
static void igt_stats_knuth_mean_variance(igt_stats_t *stats)
{
double mean = 0., m2 = 0.;
unsigned int i;
if (stats->mean_variance_valid)
return;
for (i = 0; i < stats->n_values; i++) {
double delta = stats->values[i] - mean;
mean += delta / (i + 1);
m2 += delta * (stats->values[i] - mean);
}
stats->mean = mean;
stats->variance = m2 / stats->n_values;
stats->mean_variance_valid = true;
}
double igt_stats_get_mean(igt_stats_t *stats)
{
igt_stats_knuth_mean_variance(stats);
return stats->mean;
}
double igt_stats_get_variance(igt_stats_t *stats)
{
igt_stats_knuth_mean_variance(stats);
return stats->variance;
}
|
