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gobject/performance: also print stddev of runs

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It seems useful to me to get an idea of the variance of the timing
measurements. Calculate and print the sample standard deviation of the
timings.
This commit is contained in:
Thomas Haller 2025-02-26 17:46:12 +01:00
parent 1527e1a448
commit 6610be0ef9
1 changed files with 19 additions and 1 deletions
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20
gobject/tests/performance/performance.c
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@ -78,6 +78,8 @@ run_test (PerformanceTest *test)
gpointer data = NULL;
guint64 i, num_rounds;
double elapsed, min_elapsed, max_elapsed, avg_elapsed, factor;
double var_mean = 0;
double var_m2 = 0;
GTimer *timer;
if (verbose || !quiet)
@ -183,6 +185,9 @@ run_test (PerformanceTest *test)
max_elapsed = 0.0;
for (i = 0; i < num_rounds; i++)
{
double delta;
double delta2;
test->init (test, data, factor);
g_timer_start (timer);
test->run (test, data);
@ -194,6 +199,12 @@ run_test (PerformanceTest *test)
min_elapsed = MIN (min_elapsed, elapsed);
max_elapsed = MAX (max_elapsed, elapsed);
avg_elapsed += elapsed;
/* Iteratively compute standard deviation using Welford's online algorithm. */
delta = elapsed - var_mean;
var_mean += delta / (i + 1);
delta2 = elapsed - var_mean;
var_m2 += delta * delta2;
}
if (num_rounds > 1)
@ -201,9 +212,16 @@ run_test (PerformanceTest *test)
if (verbose)
{
double sample_stddev;
if (num_rounds < 2)
sample_stddev = NAN;
else
sample_stddev = sqrt (var_m2 / (num_rounds - 1)) * 1000;
g_print ("Minimum corrected round time: %.2f msecs\n", min_elapsed * 1000);
g_print ("Average corrected round time: %.2f msecs +/- %.3f stddev\n", avg_elapsed * 1000, sample_stddev);
g_print ("Maximum corrected round time: %.2f msecs\n", max_elapsed * 1000);
g_print ("Average corrected round time: %.2f msecs\n", avg_elapsed * 1000);
}
/* Print the results */