Signed-off-by: Damien Lespiau <damien.lespiau@xxxxxxxxx> --- lib/igt_stats.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ lib/igt_stats.h | 3 +++ 2 files changed, 71 insertions(+) diff --git a/lib/igt_stats.c b/lib/igt_stats.c index 70650ec..37fcc23 100644 --- a/lib/igt_stats.c +++ b/lib/igt_stats.c @@ -25,6 +25,7 @@ #include <math.h> #include <stdlib.h> #include <string.h> +#include <time.h> #include "igt_core.h" #include "igt_stats.h" @@ -132,6 +133,73 @@ void igt_stats_init_with_size(igt_stats_t *stats, unsigned int capacity) stats->max = 0; } +/* https://en.wikipedia.org/wiki/Box%E2%80%93Muller_transform */ +static double rand_normal(double mean, double stddev) +{ + static double n2 = 0.0; + static bool n2_cached = 0; + double d, n1; + + if (!n2_cached) { + double x, y, r; + + do { + x = 2.0 * rand() / RAND_MAX - 1; + y = 2.0 * rand() / RAND_MAX - 1; + + r = x * x + y * y; + } while (r == 0.0 || r > 1.0); + + d = sqrt(-2.0 * log(r) / r); + n1 = x * d; + n2 = y * d; + + n2_cached = 1; + return n1 * stddev + mean; + } else { + n2_cached = 0; + return n2 * stddev + mean; + } +} + +static double * +igt_vector_normal(double mean, double sigma, unsigned int n_values) +{ + double *v; + unsigned int i; + + v = malloc(n_values * sizeof(double)); + srand(time(NULL)); + for (i = 0; i < n_values; i++) + v[i] = rand_normal(mean, sigma); + + return v; +} + +/** + * igt_stats_init_normal: + * @stats: An #igt_stats_t instance + * @mean: Mean of the distribution + * @std_deviation: Standard deviation of the distribution + * @n_values: Number of values to generate + * + * Generates @n_values numbers following a normal distribution defined by + * (@mean, @std_deviation). + */ +void igt_stats_init_normal(igt_stats_t *stats, + double mean, double std_deviation, + unsigned int n_values) +{ + double *v; + unsigned int i; + + v = igt_vector_normal(mean, std_deviation, n_values); + igt_stats_init_with_size(stats, n_values); + for (i = 0; i < n_values; i++) + igt_stats_push(stats, v[i]); + free(v); +} + /** * igt_stats_fini: * @stats: An #igt_stats_t instance diff --git a/lib/igt_stats.h b/lib/igt_stats.h index 554ab15..e1757b7 100644 --- a/lib/igt_stats.h +++ b/lib/igt_stats.h @@ -49,6 +49,9 @@ typedef struct { void igt_stats_init(igt_stats_t *stats); void igt_stats_init_with_size(igt_stats_t *stats, unsigned int capacity); +void igt_stats_init_normal(igt_stats_t *stats, + double mean, double std_deviation, + unsigned int n_values); void igt_stats_fini(igt_stats_t *stats); bool igt_stats_is_population(igt_stats_t *stats); void igt_stats_set_population(igt_stats_t *stats, bool full_population); -- 2.1.0 _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
