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94 lines
3 KiB
C
94 lines
3 KiB
C
/*
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* Copyright © 2006 Red Hat, Inc.
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*
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* Permission to use, copy, modify, distribute, and sell this software
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* and its documentation for any purpose is hereby granted without
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* fee, provided that the above copyright notice appear in all copies
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* and that both that copyright notice and this permission notice
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* appear in supporting documentation, and that the name of
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* the authors not be used in advertising or publicity pertaining to
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* distribution of the software without specific, written prior
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* permission. The authors make no representations about the
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* suitability of this software for any purpose. It is provided "as
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* is" without express or implied warranty.
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*
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* THE AUTHORS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS
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* SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
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* FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY SPECIAL,
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* INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
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* RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
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* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
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* IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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* Authors: Carl Worth <cworth@cworth.org>
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*/
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#include "cairo-stats.h"
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#include <assert.h>
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void
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_cairo_stats_compute (cairo_stats_t *stats,
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cairo_time_t *values,
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int num_values)
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{
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cairo_time_t sum, mean, q1, q3, iqr;
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cairo_time_t outlier_min, outlier_max;
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int i, min_valid, num_valid;
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double s;
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assert (num_values > 0);
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if (num_values == 1) {
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stats->min_ticks = stats->median_ticks = values[0];
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stats->std_dev = 0;
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stats->iterations = 1;
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return;
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}
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/* First, identify any outliers, using the definition of "mild
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* outliers" from:
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*
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* http://en.wikipedia.org/wiki/Outliers
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*
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* Which is that outliers are any values less than Q1 - 1.5 * IQR
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* or greater than Q3 + 1.5 * IQR where Q1 and Q3 are the first
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* and third quartiles and IQR is the inter-quartile range (Q3 -
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* Q1).
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*/
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qsort (values, num_values, sizeof (cairo_time_t), _cairo_time_cmp);
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q1 = values[1*num_values/4];
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q3 = values[3*num_values/4];
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/* XXX assumes we have native uint64_t */
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iqr = q3 - q1;
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outlier_min = q1 - 3 * iqr / 2;
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outlier_max = q3 + 3 * iqr / 2;
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for (i = 0; i < num_values && values[i] < outlier_min; i++)
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;
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min_valid = i;
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for (i = 0; i < num_values && values[i] <= outlier_max; i++)
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;
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num_valid = i - min_valid;
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assert(num_valid);
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stats->iterations = num_valid;
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stats->min_ticks = values[min_valid];
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stats->median_ticks = values[min_valid + num_valid / 2];
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sum = 0;
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for (i = min_valid; i < min_valid + num_valid; i++)
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sum = _cairo_time_add (sum, values[i]);
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mean = sum / num_valid;
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/* Let's use a normalized std. deviation for easier comparison. */
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s = 0;
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for (i = min_valid; i < min_valid + num_valid; i++) {
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double delta = (values[i] - mean) / (double)mean;
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s += delta * delta;
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}
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stats->std_dev = sqrt(s / num_valid);
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}
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