------- Comment #26 from victork at gcc dot gnu dot org 2008-02-11 13:41
-------
Probably, the small difference between vectorized and non-vectorized versions
can be explained by the fact that big arrays do not fit the memory cache.
Here is the version of the original program which shows that more than twice
difference is remained for long runs as well if arrays are decreased to fit the
cache:
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
typedef float ARRTYPE;
int main ( int argc, char *argv[] )
{
int m_nSamples = atoi( argv[1] );
int itBegin = atoi( argv[2] );
int itEnd = atoi( argv[3] );
int iSizeMain = atoi( argv[ 4 ] );
ARRTYPE *pSum1 = (ARRTYPE*) malloc (sizeof(ARRTYPE) *100000);
ARRTYPE *pSum = (ARRTYPE*) malloc (sizeof(ARRTYPE) *100000);
for ( int it = 0; it < 100000; it++ )
{
pSum[ it ] = it / itBegin;
pSum1[ it ] = itBegin / ( it + 1 );
}
ARRTYPE *pVec1 = (ARRTYPE*) malloc (sizeof(ARRTYPE) *100000);
for ( int i = 0, j = 0; i < m_nSamples - 5; i++ )
{
for( int it = itBegin; it < itEnd; it++ )
pVec1[ it ] += pSum[ it ] + pSum1[ it ];
}
free( pVec1 );
}
[EMAIL PROTECTED]:~> $g -O3 -fdump-tree-vect-details -fno-tree-vectorize -m64 -o
mnovec m.c
[EMAIL PROTECTED]:~> $g -O3 -fdump-tree-vect-details -ftree-vectorize -maltivec
-m64 -o mvec m.c
[EMAIL PROTECTED]:~> time ./mnovec 400000 1 29720 1000
real 0m24.493s
user 0m24.483s
sys 0m0.007s
[EMAIL PROTECTED]:~> time ./mvec 400000 1 29720 1000
real 0m10.777s
user 0m10.771s
sys 0m0.005s
-- Victor
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35117
