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Date: Tue, 08 Jan 2008 12:57:01 -0500
From: Norton Allen <allen AT huarp DOT harvard DOT edu>
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Subject: Does clock() work?
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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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