Your message dated Fri, 18 Dec 2015 19:02:29 +0100
with message-id <[email protected]>
and subject line Re: Problem of performance of pow operator in libm library on
x86_64 architecture (etch or lenny)
has caused the Debian Bug report #585430,
regarding Problem of performance of pow operator in libm library on x86_64
architecture (etch or lenny)
to be marked as done.
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If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.
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585430: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=585430
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--- Begin Message ---
Package: libc6
Status: install ok installed
Installed-Size: 11456
Architecture: amd64
Version: 2.7-18lenny2
As demonstrated by attached sample case.cc, "pow" operator evaluation,
in the case it calls "slow_pow" method, is showing very poor performances.
This problem does'nt occur on 32 bits architectures but on 64 bits ones
(lenny and etch).
Up to now, I have bypassed this problem using amd library amdlibm
instead of libc.
#include <stdio.h>
#ifdef AMDLIBM
# include <amdlibm.h>
#define ::pow amdpow
#else
# include <math.h>
#endif
//#define pow(x,y) exp(y*log(x))
int main(){
double x,x0=1.00000000000002;
x = x0;
int i;
for( i=1; i<1000; i++ ) {
if( x > x0 ) x = x0 ;
x = ::pow( x, 1.05 );
}
printf( "x = %1.30f\n", x );
}
--- End Message ---
--- Begin Message ---
Version: 2.19-1
On 2010-06-10 15:51, Lionel CHAILAN DPAM/SEMIC/LIMSI (EXT) wrote:
> Package: libc6
> Status: install ok installed
> Installed-Size: 11456
> Architecture: amd64
> Version: 2.7-18lenny2
>
> As demonstrated by attached sample case.cc, "pow" operator evaluation, in
> the case it calls "slow_pow" method, is showing very poor performances.
> This problem does'nt occur on 32 bits architectures but on 64 bits ones
> (lenny and etch).
> Up to now, I have bypassed this problem using amd library amdlibm instead of
> libc.
> #include <stdio.h>
> #ifdef AMDLIBM
> # include <amdlibm.h>
> #define ::pow amdpow
> #else
> # include <math.h>
> #endif
>
>
> //#define pow(x,y) exp(y*log(x))
> int main(){
> double x,x0=1.00000000000002;
> x = x0;
>
> int i;
> for( i=1; i<1000; i++ ) {
> if( x > x0 ) x = x0 ;
> x = ::pow( x, 1.05 );
>
> }
> printf( "x = %1.30f\n", x );
> }
>
This problem has been solved in the jessie version. I am therefore
closing the bug.
Aurelien
--
Aurelien Jarno GPG: 4096R/1DDD8C9B
[email protected] http://www.aurel32.net
--- End Message ---
