problem with clock()

I want to calculate the time elapsed since the execution of take_forks() but the value of "b" and "end"are always 0.Why this happens?

Code:

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clock_t start,end;
        start=clock();//clocks before taking the forks
        take_forks(i);
        end=clock();//clocks after taking forks
       
       
        double b=(double)(end-start)/(double)(CLOCKS_PER_SEC);

tmesos=tmesos+(b/counter)/n;
printf("waiting time is %f",b);

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And what is the value of start?

CLOCKS_PER_SEC is usually 1000 on most systems. Perhaps the code you benchmarked ran fast enough and took less than 1ms?

The value of start is also 0.On failure clock() returns -1 thus it did not failed. Is there another way to benchmark my function?

Quote:

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Originally Posted by killbill689

The value of start is also 0.On failure clock() returns -1 thus it did not failed. Is there another way to benchmark my function?

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On Windows, QueryPerformanceFrequency() and QueryPerformanceCounter(). On Linux and similar, gettimeofday(). I think gettimeofday() works on OSX too but I'm not sure.

These functions have better resolution than clock().

I used gettimeofday() but i have the same problem

Code:

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struct timeval start,end;

        gettimeofday(&start,NULL);
        take_forks(i);
        gettimeofday(&end,NULL);

double b=(double)(end.tv_usec-start.tv_usec);

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