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From: "burnus at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/31723] Use reciprocal and reciprocal square root with -ffast-math
Date: Fri, 27 Apr 2007 11:41:00 -0000 [thread overview]
Message-ID: <20070427114133.23693.qmail@sourceware.org> (raw)
In-Reply-To: <bug-31723-11659@http.gcc.gnu.org/bugzilla/>
------- Comment #7 from burnus at gcc dot gnu dot org 2007-04-27 12:41 -------
> (float) time for 1.0 / sqrt = 5.96 sec (res = 2.8450581250000000e+05)
> (float) time for rsqrt = 2.49 sec (res = 2.2360225000000000e+05)
> (double) time for 1.0 / sqrt = 7.35 sec (res = 5.9926234364635509e+05)
> (double) time for rsqrt = 7.49 sec (res = 5.9926234364355623e+05)
On an Athlon 64 2x, the double result is more favourable for rsqrt
(using the system g++ 4.1.2 with g++ -march=opteron -O3 -ftree-vectorize
-funroll-loops -funit-at-a-time -msse3 frsqrt.cc; similarly with -ffast-math)
(float) time for 1.0 / sqrt = 3.76 sec (res = 1.7943843750000000e+05)
(float) time for rsqrt = 1.72 sec (res = 1.7943843750000000e+05)
(double) time for 1.0 / sqrt = 5.15 sec (res = 5.9926234364320245e+05)
(double) time for rsqrt = 3.34 sec (res = 5.9926234364320245e+05)
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31723
next prev parent reply other threads:[~2007-04-27 11:41 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-27 8:07 [Bug middle-end/31723] New: " jb at gcc dot gnu dot org
2007-04-27 9:16 ` [Bug middle-end/31723] " burnus at gcc dot gnu dot org
2007-04-27 9:45 ` rguenth at gcc dot gnu dot org
2007-04-27 10:27 ` jb at gcc dot gnu dot org
2007-04-27 10:29 ` jb at gcc dot gnu dot org
2007-04-27 11:01 ` jb at gcc dot gnu dot org
2007-04-27 11:09 ` rguenth at gcc dot gnu dot org
2007-04-27 11:41 ` burnus at gcc dot gnu dot org [this message]
2007-04-27 20:43 ` steven at gcc dot gnu dot org
2007-04-27 21:03 ` rguenth at gcc dot gnu dot org
2007-04-27 23:25 ` pinskia at gcc dot gnu dot org
2007-06-10 8:28 ` ubizjak at gmail dot com
2007-06-10 10:47 ` ubizjak at gmail dot com
2007-06-10 11:06 ` jb at gcc dot gnu dot org
2007-06-10 12:07 ` rguenth at gcc dot gnu dot org
2007-06-10 12:09 ` rguenth at gcc dot gnu dot org
2007-06-10 16:25 ` ubizjak at gmail dot com
2007-06-10 16:49 ` ubizjak at gmail dot com
2007-06-10 17:34 ` ubizjak at gmail dot com
2007-06-10 21:39 ` rguenther at suse dot de
2007-06-10 21:47 ` rguenth at gcc dot gnu dot org
2007-06-10 21:48 ` rguenth at gcc dot gnu dot org
2007-06-11 3:32 ` tbptbp at gmail dot com
2007-06-11 5:51 ` ubizjak at gmail dot com
2007-06-11 5:58 ` tbptbp at gmail dot com
2007-06-13 20:21 ` ubizjak at gmail dot com
2007-06-14 9:18 ` ubizjak at gmail dot com
2007-06-15 13:23 ` burnus at gcc dot gnu dot org
2007-06-16 9:53 ` uros at gcc dot gnu dot org
2007-06-18 8:56 ` ubizjak at gmail dot com
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