problem with clock()

[killbill689]

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?

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);

[VictorN]

And what is the value of start?

[Bssldr]

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

[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?

[Lindley]

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?

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().

[killbill689]

I used gettimeofday() but i have the same problem

struct timeval start,end;

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

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