ffe4f3c0d1
Need an initialization function to set min to -1 to differentiate from an actual min of 0. Signed-off-by: David Ahern <dsahern@gmail.com> Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Runzhen Wang <runzhen@linux.vnet.ibm.com> Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Link: http://lkml.kernel.org/r/1375473947-64285-3-git-send-email-dsahern@gmail.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
63 lines
1 KiB
C
63 lines
1 KiB
C
#include <math.h>
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#include "stat.h"
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void update_stats(struct stats *stats, u64 val)
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{
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double delta;
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stats->n++;
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delta = val - stats->mean;
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stats->mean += delta / stats->n;
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stats->M2 += delta*(val - stats->mean);
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if (val > stats->max)
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stats->max = val;
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if (val < stats->min)
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stats->min = val;
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}
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double avg_stats(struct stats *stats)
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{
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return stats->mean;
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}
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/*
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* http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance
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*
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* (\Sum n_i^2) - ((\Sum n_i)^2)/n
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* s^2 = -------------------------------
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* n - 1
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*
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* http://en.wikipedia.org/wiki/Stddev
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*
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* The std dev of the mean is related to the std dev by:
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*
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* s
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* s_mean = -------
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* sqrt(n)
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*
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*/
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double stddev_stats(struct stats *stats)
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{
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double variance, variance_mean;
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if (stats->n < 2)
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return 0.0;
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variance = stats->M2 / (stats->n - 1);
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variance_mean = variance / stats->n;
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return sqrt(variance_mean);
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}
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double rel_stddev_stats(double stddev, double avg)
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{
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double pct = 0.0;
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if (avg)
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pct = 100.0 * stddev/avg;
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return pct;
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}
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