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author | avg <avg@FreeBSD.org> | 2017-05-24 11:10:55 +0000 |
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committer | avg <avg@FreeBSD.org> | 2017-05-24 11:10:55 +0000 |
commit | 583eac3f4774630c62cfc22325fa610b1e315a84 (patch) | |
tree | efd9b83ead00ad0a2fbf2a423232d43569117f97 /cddl/contrib/opensolaris | |
parent | e6c8fed348e54303d81af9de2755b0f5494234ff (diff) | |
download | FreeBSD-src-583eac3f4774630c62cfc22325fa610b1e315a84.zip FreeBSD-src-583eac3f4774630c62cfc22325fa610b1e315a84.tar.gz |
MFC r316853: dtrace: fix normalization of stddev aggregation
Sponsored by: Panzura
Diffstat (limited to 'cddl/contrib/opensolaris')
-rw-r--r-- | cddl/contrib/opensolaris/lib/libdtrace/common/dt_consume.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/cddl/contrib/opensolaris/lib/libdtrace/common/dt_consume.c b/cddl/contrib/opensolaris/lib/libdtrace/common/dt_consume.c index 04c022b..98dc29a 100644 --- a/cddl/contrib/opensolaris/lib/libdtrace/common/dt_consume.c +++ b/cddl/contrib/opensolaris/lib/libdtrace/common/dt_consume.c @@ -389,8 +389,10 @@ dt_stddev(uint64_t *data, uint64_t normal) * The standard approximation for standard deviation is * sqrt(average(x**2) - average(x)**2), i.e. the square root * of the average of the squares minus the square of the average. + * When normalizing, we should divide the sum of x**2 by normal**2. */ dt_divide_128(data + 2, normal, avg_of_squares); + dt_divide_128(avg_of_squares, normal, avg_of_squares); dt_divide_128(avg_of_squares, data[0], avg_of_squares); norm_avg = (int64_t)data[1] / (int64_t)normal / (int64_t)data[0]; |