Date: Wed, 24 May 2017 11:10:56 +0000 (UTC) From: Andriy Gapon <avg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-11@freebsd.org Subject: svn commit: r318783 - stable/11/cddl/contrib/opensolaris/lib/libdtrace/common Message-ID: <201705241110.v4OBAujr068655@repo.freebsd.org>
next in thread | raw e-mail | index | archive | help
Author: avg Date: Wed May 24 11:10:55 2017 New Revision: 318783 URL: https://svnweb.freebsd.org/changeset/base/318783 Log: MFC r316853: dtrace: fix normalization of stddev aggregation Sponsored by: Panzura Modified: stable/11/cddl/contrib/opensolaris/lib/libdtrace/common/dt_consume.c Directory Properties: stable/11/ (props changed) Modified: stable/11/cddl/contrib/opensolaris/lib/libdtrace/common/dt_consume.c ============================================================================== --- stable/11/cddl/contrib/opensolaris/lib/libdtrace/common/dt_consume.c Wed May 24 11:09:06 2017 (r318782) +++ stable/11/cddl/contrib/opensolaris/lib/libdtrace/common/dt_consume.c Wed May 24 11:10:55 2017 (r318783) @@ -389,8 +389,10 @@ dt_stddev(uint64_t *data, uint64_t norma * 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];
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201705241110.v4OBAujr068655>