Mail Archives: cygwin/2008/01/08/13:30:51
CLOCKS_PER_SEC is a machine dependent macro, but not so machine dependent to
recognize that my 32-bit windows box has dual processors. Not useful for
benchmarking, is it.
clock is not the way to go. It is a crude estimation of processor time. On
regular UNIX times(2) is the function to use -- cygwin does not seem to have
it.
I don't know if this helps, but:
My cygwin reports
$ ./chktime
CLOCKS_PER_SEC = 1000
clock() = 31
clock() = 31
clock() = 31
clock() = 31
clock() = 31
clock() = 31
clock() = 31
clock() = 31
My 64-bit Fedora/Linux reports
# ./chktime
CLOCKS_PER_SEC = 1000000
clock() = 0
clock() = 0
clock() = 0
clock() = 0
clock() = 0
clock() = 0
clock() = 0
clock() = 0
-----Original Message-----
From: cygwin-owner AT cygwin DOT com [mailto:cygwin-owner AT cygwin DOT com] On Behalf Of
Norton Allen
Sent: Tuesday, January 08, 2008 12:57 PM
To: cygwin AT cygwin DOT com
Subject: Does clock() work?
I am trying to write a benchmark application, and figured I'd use
clock() for sub-second resolution timing, but I got non-sensical results. I
check the cygwin archives, but the only mention I saw was that clock()
didn't work on Win98. Here's my test code, chktime.c:
#include <time.h>
#include <unistd.h>
#include <stdio.h>
int main( int argc, char **argv ) {
clock_t cur_time, cps = CLOCKS_PER_SEC;
int i;
printf( "CLOCKS_PER_SEC = %ld\n", cps );
for ( i = 0; i < 8; i++ ) {
sleep(1);
cur_time = clock();
printf( "clock() = %ld\n", cur_time );
}
return 0;
}
and here's the output I get:
Cygwin> ./chktime
CLOCKS_PER_SEC = 1000
clock() = 171
clock() = 171
clock() = 171
clock() = 171
clock() = 171
clock() = 171
clock() = 171
clock() = 171
Cygwin>
I would expect the clock() values to increase by approximately 1000 on each
iteration. (Yes, the sleep() seems to be working, as the lines come out at
about 1 Hz.)
Is this a known problem? Do others get this result, or do I have a corrupted
library?
-Norton Allen
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