Best timing method in C?

Question

What is the best way to time a code section with high resolution and portability?

/* Time from here */
ProcessIntenseFunction();
/* to here. */

printf(\"Tim         


        

Answer 1

High resolution is relative... I was looking at the examples and they mostly cater for milliseconds. However for me it is important to measure microseconds. I have not seen a platform independant solution for microseconds and thought something like the code below will be usefull. I was timing on windows only for the time being and will most likely add a gettimeofday() implementation when doing the same on AIX/Linux.

    #ifdef WIN32
      #ifndef PERFTIME
        #include 
        #include 
        #define PERFTIME_INIT unsigned __int64 freq;  QueryPerformanceFrequency((LARGE_INTEGER*)&freq); double timerFrequency = (1.0/freq);  unsigned __int64 startTime;  unsigned __int64 endTime;  double timeDifferenceInMilliseconds;
        #define PERFTIME_START QueryPerformanceCounter((LARGE_INTEGER *)&startTime);
        #define PERFTIME_END QueryPerformanceCounter((LARGE_INTEGER *)&endTime); timeDifferenceInMilliseconds = ((endTime-startTime) * timerFrequency);  printf("Timing %fms\n",timeDifferenceInMilliseconds);
    #define PERFTIME(funct) {unsigned __int64 freq;  QueryPerformanceFrequency((LARGE_INTEGER*)&freq);  double timerFrequency = (1.0/freq);  unsigned __int64 startTime;  QueryPerformanceCounter((LARGE_INTEGER *)&startTime);  unsigned __int64 endTime;  funct; QueryPerformanceCounter((LARGE_INTEGER *)&endTime);  double timeDifferenceInMilliseconds = ((endTime-startTime) * timerFrequency);  printf("Timing %fms\n",timeDifferenceInMilliseconds);}
      #endif
    #else
      //AIX/Linux gettimeofday() implementation here
    #endif

Usage:

PERFTIME(ProcessIntenseFunction());

or

PERFTIME_INIT
PERFTIME_START
ProcessIntenseFunction()
PERFTIME_END