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Date: Thu, 21 Feb 2008 12:00:00 -0000
From: "grugh at centrum dot cz" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sources.redhat.com
Message-ID: <20080221115945.5782.grugh@centrum.cz>
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Subject: [Bug math/5782] New: Slow sine function for special values on AMD64 - second attempt
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I would like to repost my previously deleted bug by (lazy IMHO)
carlos@codesoucery.com. The math sin function is at least 1000x slower on 64bit
distributions for special numbers (and carlos dosn't care about it). 
I can't try it with CVS head, because I cannot connect to cvs through our firewall.
But even when I tried the latest snapshot, I couldn't build it (maybe another bug):
a - elf/dl-vdso.os
: /home/inova/projects/glibc/build/libc_pic.a
gcc   -nostdlib -nostartfiles -r -o
/home/inova/projects/glibc/build/elf/librtld.map.o '-Wl,-('
/home/inova/projects/glibc/build/elf/dl-allobjs.os
/home/inova/projects/glibc/build/libc_pic.a -lgcc '-Wl,-)'
-Wl,-Map,/home/inova/projects/glibc/build/elf/librtld.mapT
/home/inova/projects/glibc/build/libc_pic.a(init-first.os):(.data+0x0): multiple
definition of `__libc_multiple_libcs'
/home/inova/projects/glibc/build/elf/dl-allobjs.os:/home/inova/projects/glibc/src/glibc-20080218/elf/rtld.c:641:
first defined here
/home/inova/projects/glibc/build/libc_pic.a(dl-addr.os): In function
`_dl_addr_inside_object':
/home/inova/projects/glibc/src/glibc-20080218/elf/dl-addr.c:158: multiple
definition of `_dl_addr_inside_object'
/home/inova/projects/glibc/build/elf/dl-allobjs.os:/home/inova/projects/glibc/src/glibc-20080218/elf/dl-open.c:700:
first defined here
collect2: ld returned 1 exit status
make[2]: *** [/home/inova/projects/glibc/build/elf/librtld.map] Error 1
make[2]: Leaving directory `/home/inova/projects/glibc/src/glibc-20080218/elf'
make[1]: *** [elf/subdir_lib] Error 2
make[1]: Leaving directory `/home/inova/projects/glibc/src/glibc-20080218'
make: *** [all] Error 2 

Please, anyone with 64bit distribution and glibc CVS head, could you try the
attached example and post the time results of it? (or help me to build the
snapshot...)
Thank you

====== Original bug report ======================================
The math sin(double) function is in 64bit distribution (Kubuntu 7.10 AMD64 and
Fedora - unknown version) unreasonable slow (~400 microseconds on Atlon64 X2
4800+!!!) for some special values. In 32bit distribution is everything fine.
I captured some of those values:
0.93340582292648832662962377071381  0x3fedde75e36bb000
2.3328432680770916363144351635128   0x4002a9a9bb38add0
3.7439477503636453548097051680088   0x400df39ae0cdf500
3.9225160069792437411706487182528   0x400f615012801950
4.0711651639931289992091478779912   0x401048df854fdc20
4.7858438478542097982426639646292   0x401324b43fe92fc0
5.9840767662578002727968851104379   0x4017efb1d1df52a0

Example:
#include <math.h>
int main(int argc, char** argv) {
    volatile double value = 0.93340582292648832662962377071381;
    volatile double out;
    int i;
    for (i=0; i < 20000; i++)
        out = sin(value);
    return 0;
}

-- 
           Summary: Slow sine function for special values on AMD64 - second
                    attempt
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
        AssignedTo: aj at suse dot de
        ReportedBy: grugh at centrum dot cz
                CC: glibc-bugs at sources dot redhat dot com
  GCC host triplet: x86_64-unknown-linux-gnu


http://sourceware.org/bugzilla/show_bug.cgi?id=5782

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