C++ Elapsed time is 0

Question

The problem is that my program is so fast that it doesn't detect change in time, or GetTickCount(), how can i prevent this from happening?

Thank You

You can try something more precise if it's taking less than a millisecond. `QueryPerformanceCounter` would be a good start, or the new-ish `` header. — chris, Nov 17 '12 at 01:46

score 0 · Answer 1 · answered Nov 17 '12 at 01:43

0

Are you printing the running time as an integer? If you are doing division to get the elapsed time, cast the numerator or denominator as a float.

answered Nov 17 '12 at 01:43

Chris

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score 0 · Answer 2 · answered Nov 17 '12 at 01:45

0

Time how long x runs take and take an average.

Additionally you can use profiling for an accurate timing.

answered Nov 17 '12 at 01:45

Casey

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score 0 · Answer 3 · answered Nov 17 '12 at 02:26

0

Use

void WINAPI GetSystemTimeAsFileTime(
  _Out_  LPFILETIME lpSystemTimeAsFileTime
);

instead. It has better resolution. In majority of cases this is really what is needed.

answered Nov 17 '12 at 02:26

Kirill Kobelev

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score 0 · Answer 4 · answered Nov 17 '12 at 07:36

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There's a very handy class on CodeProject that wraps QueryPerformanceCounter, that I use often: http://www.codeproject.com/Articles/475/The-CPerfTimer-timer-class

answered Nov 17 '12 at 07:36

Jonathan Potter

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score 0 · Accepted Answer · answered Nov 17 '12 at 08:14

0

GetTickCount has 5..15 millisecond precision, so "zero time difference" is a common problem.

If you need precision, use QueryPerformanceCounter.

answered Nov 17 '12 at 08:14

SigTerm

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score -2 · Answer 6 · edited May 23 '17 at 12:12

-2

Or you can try using rtdsc. for details see here: http://www.mcs.anl.gov/~kazutomo/rdtsc.html Snippet:

#include <stdio.h>
#include "rdtsc.h"

int main(int argc, char* argv[])
{
  unsigned long long a,b;

  a = rdtsc();
  b = rdtsc();

  printf("%llu\n", b-a);
  return 0;
}

Or even chrono is good, but then it needs C++11 compliance (in part). details: std::chrono and cout

edited May 23 '17 at 12:12

Community

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answered Nov 17 '12 at 02:11

Sarang

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Bad idea - on multicore cpus. – SigTerm Nov 17 '12 at 08:10
Dear Friends, I know this is bad idea on multicore cpus, but it works to find out time elapsed in the case specified. – Sarang Dec 01 '12 at 03:33

C++ Elapsed time is 0

6 Answers6