Is anyone with this problem *not* running ubuntu?
Me - RHEL 5.2 opteron:
Python 2.6.1 (r261:67515, Jan 5 2009, 10:19:01)
[GCC 4.1.2 20071124 (Red Hat 4.1.2-42)] on linux2
Fedora 9 PS3/PPC:
Python 2.5.1 (r251:54863, Jul 17 2008, 13:25:23)
[GCC 4.3.1 20080708 (Red Hat 4.3.1-4)] on linux2
Actually I now have some interesting results that indicate the issue
isn't in Python or NumPy at all. I just wrote a C program to try to
reproduce the error, and was able to do so (actually the difference is
even larger).
Opteron:
float (32) time in usecs: 179698
double (64) time in usecs: 13795
PS3/PPC:
float (32) time in usecs: 614821
double (64) time in usecs: 37163
I've attached the code for others to review and/or try out. I guess
this is worth showing to the libc people?
Andrew
#include <stdio.h>
#include <math.h>
#include <sys/time.h>
#define LEN 159161
float inp32[LEN];
float out32[LEN];
double inp64[LEN];
double out64[LEN];
int main(int argc, char** argv)
{
struct timeval tv_start;
struct timeval tv_stop;
int i;
for(i = 0; i < LEN; i++) {
//inp32[i] = ((float)i / (float)LEN) * (2 * M_PI);
inp32[i] = (float)i;
out32[i] = 0.0;
}
gettimeofday(&tv_start, NULL);
for(i = 0; i < LEN; i++) {
out32[i] = (float)cosf((float)inp32[i]);
}
gettimeofday(&tv_stop, NULL);
if(tv_start.tv_sec != tv_stop.tv_sec) {
puts("seconds changed, re-run the benchmark");
}
printf("float (32) time in usecs: %d\n", tv_stop.tv_usec -
tv_start.tv_usec);
for(i = 0; i < LEN; i++) {
//inp32[i] = ((double)i / (double)LEN) * (2 * M_PI);
inp64[i] = (float)i;
out64[i] = 0.0;
}
gettimeofday(&tv_start, NULL);
for(i = 0; i < LEN; i++) {
out64[i] = (double)cos((double)inp64[i]);
}
gettimeofday(&tv_stop, NULL);
if(tv_start.tv_sec != tv_stop.tv_sec) {
puts("seconds changed, re-run the benchmark");
}
printf("double (64) time in usecs: %d\n", tv_stop.tv_usec -
tv_start.tv_usec);
return 0;
}
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