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From: "jvdelisle at gcc dot gnu dot org" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sources.redhat.com
Subject: [Bug math/5997] New: Very slow execution of sinf function
Date: Sat, 29 Mar 2008 21:18:00 -0000 [thread overview]
Message-ID: <20080329211738.5997.jvdelisle@gcc.gnu.org> (raw)
With this test case:
#include <stdio.h>
#include <math.h>
unsigned int ta;
main ()
{
double result;
for (ta = 1; ta <= 8000000; ta++)
{
result = sin(ta * 3.14159);
}
printf("result = \t%.13e\n", result);
}
Using sin vs sinf.
sin:
$ time ./a.out
result = -6.9068092664138e-01
real 0m0.782s
user 0m0.778s
sys 0m0.004s
sinf:
$ time ./a.out
result = -6.9068092107773e-01
real 0m8.622s
user 0m8.605s
sys 0m0.009s
The difference in assembly code (-S output):
44,47c44,47
< call sin
< movsd %xmm0, -40(%rbp)
< movq -40(%rbp), %rax
< movq %rax, -8(%rbp)
---
> cvtsd2ss %xmm0, %xmm0
> call sinf
> cvtss2sd %xmm0, %xmm0
> movsd %xmm0, -8(%rbp)
I don't think the conversion functions should account for this huge time
difference. Also with -m32 and sinf I get:
$ time ./a.out
result = -6.9068092664141e-01
real 0m1.157s
user 0m0.765s
sys 0m0.002s
Which is more reasonable.
$ gcc -v
Using built-in specs.
Target: x86_64-redhat-linux
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --enable-shared --enable-threads=posix
--enable-checking=release --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions
--enable-languages=c,c++,objc,obj-c++,java,fortran,ada --enable-java-awt=gtk
--disable-dssi --enable-plugin
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-1.5.0.0/jre
--enable-libgcj-multifile --enable-java-maintainer-mode
--with-ecj-jar=/usr/share/java/eclipse-ecj.jar --with-cpu=generic
--host=x86_64-redhat-linux
Thread model: posix
gcc version 4.1.2 20070925 (Red Hat 4.1.2-33)
I am running latest Fedora 8
See also gfortran bug pr34128.
--
Summary: Very slow execution of sinf function
Product: glibc
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: math
AssignedTo: aj at suse dot de
ReportedBy: jvdelisle at gcc dot gnu dot org
CC: glibc-bugs at sources dot redhat dot com
GCC host triplet: x86_64-unknown-linux-gnu
GCC target triplet: x86_64-redhat-linux-gnu
http://sourceware.org/bugzilla/show_bug.cgi?id=5997
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next reply other threads:[~2008-03-29 21:18 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-29 21:18 jvdelisle at gcc dot gnu dot org [this message]
2008-03-29 22:13 ` [Bug math/5997] " fxcoudert at gcc dot gnu dot org
2008-03-30 0:10 ` jvdelisle at gcc dot gnu dot org
2008-07-14 13:45 ` grugh at centrum dot cz
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