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  Time taken  d seconds  d milliseconds   sec  msec     Is there a standard library that would have a cross-platform solution

User · Accepted Answer

I think this should work    include  lt time h gt   clock t start   clock    diff  ProcessIntenseFunction    diff   clock   - start   int msec   diff   1000   CLOCKS PER SEC  printf  Time taken  d seconds  d milliseconds   msec 1000  msec 1000

User · Answer

If you don t want CPU time then I think what you re looking for is the timeval struct   I use the below for calculating execution time   int timeval subtract struct timeval  result                                                                                                                                                               struct timeval end                                                                                                                                                                        struct timeval start                                                                                                                                                                                                                                                                                                                                              if  start tv usec  lt  end tv usec                                                                                                                                                              int nsec    end tv usec - start tv usec    1000000   1                                                                                                                               end tv usec -  1000000   nsec                                                                                                                                                        end tv sec    nsec                                                                                                                                                                                                                                                                                                                                                if  start tv usec - end tv usec  gt  1000000                                                                                                                                                    int nsec    end tv usec - start tv usec    1000000                                                                                                                                   end tv usec    1000000   nsec                                                                                                                                                        end tv sec -  nsec                                                                                                                                                                                                                                                                                                                                                 result- gt tv sec   end tv sec - start tv sec                                                                                                                                           result- gt tv usec   end tv usec - start tv usec                                                                                                                                         return end tv sec  lt  start tv sec                                                                                                                                                                                                                                                                                                                                   void set exec time int end                                                                                                                                                                                                                                                                                                                                                        static struct timeval time start                                                                                                                                                     struct timeval time end                                                                                                                                                              struct timeval time diff                                                                                                                                                              if  end                                                                                                                                                                                      gettimeofday  amp time end  NULL                                                                                                                                                         if  timeval subtract  amp time diff  time end  time start     0                                                                                                                                  if  end    1                                                                                                                                                                                 printf   nexec time   1 2fs n                                                                                                                                                                time diff tv sec    time diff tv usec   1000000 0f                                                                                                                   else if  end    2                                                                                                                                                                            printf   1 2fs                                                                                                                                                                               time diff tv sec    time diff tv usec   1000000 0f                                                                                                                                                                                                                                                                                                return                                                                                                                                                                                                                                                                                                                                                            gettimeofday  amp time start  NULL                                                                                                                                                                                                                                                                                                                                     void start exec timer                                                                                                                                                                                                                                                                                                                                                             set exec time 0                                                                                                                                                                                                                                                                                                                                                    void print exec timer                                                                                                                                                                                                                                                                                                                                                             set exec time 1

User · Answer

If you don t want CPU time then I think what you re looking for is the timeval struct   I use the below for calculating execution time   int timeval subtract struct timeval  result                                                                                                                                                               struct timeval end                                                                                                                                                                        struct timeval start                                                                                                                                                                                                                                                                                                                                              if  start tv usec  lt  end tv usec                                                                                                                                                              int nsec    end tv usec - start tv usec    1000000   1                                                                                                                               end tv usec -  1000000   nsec                                                                                                                                                        end tv sec    nsec                                                                                                                                                                                                                                                                                                                                                if  start tv usec - end tv usec  gt  1000000                                                                                                                                                    int nsec    end tv usec - start tv usec    1000000                                                                                                                                   end tv usec    1000000   nsec                                                                                                                                                        end tv sec -  nsec                                                                                                                                                                                                                                                                                                                                                 result- gt tv sec   end tv sec - start tv sec                                                                                                                                           result- gt tv usec   end tv usec - start tv usec                                                                                                                                         return end tv sec  lt  start tv sec                                                                                                                                                                                                                                                                                                                                   void set exec time int end                                                                                                                                                                                                                                                                                                                                                        static struct timeval time start                                                                                                                                                     struct timeval time end                                                                                                                                                              struct timeval time diff                                                                                                                                                              if  end                                                                                                                                                                                      gettimeofday  amp time end  NULL                                                                                                                                                         if  timeval subtract  amp time diff  time end  time start     0                                                                                                                                  if  end    1                                                                                                                                                                                 printf   nexec time   1 2fs n                                                                                                                                                                time diff tv sec    time diff tv usec   1000000 0f                                                                                                                   else if  end    2                                                                                                                                                                            printf   1 2fs                                                                                                                                                                               time diff tv sec    time diff tv usec   1000000 0f                                                                                                                                                                                                                                                                                                return                                                                                                                                                                                                                                                                                                                                                            gettimeofday  amp time start  NULL                                                                                                                                                                                                                                                                                                                                     void start exec timer                                                                                                                                                                                                                                                                                                                                                             set exec time 0                                                                                                                                                                                                                                                                                                                                                    void print exec timer                                                                                                                                                                                                                                                                                                                                                             set exec time 1

User · Answer

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  lt windows h gt           include  lt winbase h gt           define PERFTIME INIT unsigned   int64 freq   QueryPerformanceFrequency  LARGE INTEGER   amp freq   double timerFrequency    1 0 freq    unsigned   int64 startTime   unsigned   int64 endTime   double timeDifferenceInMilliseconds           define PERFTIME START QueryPerformanceCounter  LARGE INTEGER    amp startTime            define PERFTIME END QueryPerformanceCounter  LARGE INTEGER    amp endTime   timeDifferenceInMilliseconds     endTime-startTime    timerFrequency    printf  Timing  fms n  timeDifferenceInMilliseconds        define PERFTIME funct   unsigned   int64 freq   QueryPerformanceFrequency  LARGE INTEGER   amp freq    double timerFrequency    1 0 freq    unsigned   int64 startTime   QueryPerformanceCounter  LARGE INTEGER    amp startTime    unsigned   int64 endTime   funct  QueryPerformanceCounter  LARGE INTEGER    amp 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

User · Answer

gettimeofday will return time accurate to microseconds within the resolution of the system clock   You might also want to check out the High Res Timers project on SourceForge

User · Answer

gettimeofday   will probably do what you want   If you re on Intel hardware  here s how to read the CPU real-time instruction counter   It will tell you the number of CPU cycles executed since the processor was booted   This is probably the finest-grained  lowest overhead counter you can get for performance measurement   Note that this is the number of CPU cycles   On linux you can get the CPU speed from  proc cpuinfo and divide to get the number of seconds   Converting this to a double is quite handy   When I run this on my box  I get   11867927879484732 11867927879692217 it took this long to call printf  207485   Here s the Intel developer s guide that  gives tons of detail    include  lt stdio h gt   include  lt stdint h gt   inline uint64 t rdtsc         uint32 t lo  hi        asm     volatile            xorl   eax    eax n         cpuid n         rdtsc n            a   lo     d   hi                    ebx     ecx        return  uint64 t hi  lt  lt  32   lo     main         unsigned long long x      unsigned long long y      x   rdtsc        printf   lld n  x       y   rdtsc        printf   lld n  y       printf  it took this long to call printf   lld n  y-x

User · Answer

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  lt windows h gt           include  lt winbase h gt           define PERFTIME INIT unsigned   int64 freq   QueryPerformanceFrequency  LARGE INTEGER   amp freq   double timerFrequency    1 0 freq    unsigned   int64 startTime   unsigned   int64 endTime   double timeDifferenceInMilliseconds           define PERFTIME START QueryPerformanceCounter  LARGE INTEGER    amp startTime            define PERFTIME END QueryPerformanceCounter  LARGE INTEGER    amp endTime   timeDifferenceInMilliseconds     endTime-startTime    timerFrequency    printf  Timing  fms n  timeDifferenceInMilliseconds        define PERFTIME funct   unsigned   int64 freq   QueryPerformanceFrequency  LARGE INTEGER   amp freq    double timerFrequency    1 0 freq    unsigned   int64 startTime   QueryPerformanceCounter  LARGE INTEGER    amp startTime    unsigned   int64 endTime   funct  QueryPerformanceCounter  LARGE INTEGER    amp 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

User · Answer

gettimeofday will return time accurate to microseconds within the resolution of the system clock   You might also want to check out the High Res Timers project on SourceForge

User · Answer

gettimeofday   will probably do what you want   If you re on Intel hardware  here s how to read the CPU real-time instruction counter   It will tell you the number of CPU cycles executed since the processor was booted   This is probably the finest-grained  lowest overhead counter you can get for performance measurement   Note that this is the number of CPU cycles   On linux you can get the CPU speed from  proc cpuinfo and divide to get the number of seconds   Converting this to a double is quite handy   When I run this on my box  I get   11867927879484732 11867927879692217 it took this long to call printf  207485   Here s the Intel developer s guide that  gives tons of detail    include  lt stdio h gt   include  lt stdint h gt   inline uint64 t rdtsc         uint32 t lo  hi        asm     volatile            xorl   eax    eax n         cpuid n         rdtsc n            a   lo     d   hi                    ebx     ecx        return  uint64 t hi  lt  lt  32   lo     main         unsigned long long x      unsigned long long y      x   rdtsc        printf   lld n  x       y   rdtsc        printf   lld n  y       printf  it took this long to call printf   lld n  y-x

User · Answer

gettimeofday will return time accurate to microseconds within the resolution of the system clock   You might also want to check out the High Res Timers project on SourceForge

User · Answer

gettimeofday   will probably do what you want   If you re on Intel hardware  here s how to read the CPU real-time instruction counter   It will tell you the number of CPU cycles executed since the processor was booted   This is probably the finest-grained  lowest overhead counter you can get for performance measurement   Note that this is the number of CPU cycles   On linux you can get the CPU speed from  proc cpuinfo and divide to get the number of seconds   Converting this to a double is quite handy   When I run this on my box  I get   11867927879484732 11867927879692217 it took this long to call printf  207485   Here s the Intel developer s guide that  gives tons of detail    include  lt stdio h gt   include  lt stdint h gt   inline uint64 t rdtsc         uint32 t lo  hi        asm     volatile            xorl   eax    eax n         cpuid n         rdtsc n            a   lo     d   hi                    ebx     ecx        return  uint64 t hi  lt  lt  32   lo     main         unsigned long long x      unsigned long long y      x   rdtsc        printf   lld n  x       y   rdtsc        printf   lld n  y       printf  it took this long to call printf   lld n  y-x

User · Answer

gettimeofday will return time accurate to microseconds within the resolution of the system clock   You might also want to check out the High Res Timers project on SourceForge

User · Answer

I use SDL GetTicks from the SDL library

User · Answer

I use SDL GetTicks from the SDL library

User · Answer

I use SDL GetTicks from the SDL library

User · Answer

I use SDL GetTicks from the SDL library

User · Answer

gettimeofday   will probably do what you want   If you re on Intel hardware  here s how to read the CPU real-time instruction counter   It will tell you the number of CPU cycles executed since the processor was booted   This is probably the finest-grained  lowest overhead counter you can get for performance measurement   Note that this is the number of CPU cycles   On linux you can get the CPU speed from  proc cpuinfo and divide to get the number of seconds   Converting this to a double is quite handy   When I run this on my box  I get   11867927879484732 11867927879692217 it took this long to call printf  207485   Here s the Intel developer s guide that  gives tons of detail    include  lt stdio h gt   include  lt stdint h gt   inline uint64 t rdtsc         uint32 t lo  hi        asm     volatile            xorl   eax    eax n         cpuid n         rdtsc n            a   lo     d   hi                    ebx     ecx        return  uint64 t hi  lt  lt  32   lo     main         unsigned long long x      unsigned long long y      x   rdtsc        printf   lld n  x       y   rdtsc        printf   lld n  y       printf  it took this long to call printf   lld n  y-x

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