How do I measure a time interval in C?

Question

I would like to measure time in C, and I am having a tough time figuring it out, all I want is something like this:

• start a timer
• run a method
• stop the timer
• report the time taken (at least to micro accuracy)

Any help would be appreciated.

(I am compiling in windows using mingw)

Answer 1

High resolution timers that provide a resolution of 1 microsecond are system-specific, so you will have to use different methods to achieve this on different OS platforms. You may be interested in checking out the following article, which implements a cross-platform C++ timer class based on the functions described below:

• [Song Ho Ahn - High Resolution Timer][1]

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Windows

The Windows API provides extremely high resolution timer functions: QueryPerformanceCounter(), which returns the current elapsed ticks, and QueryPerformanceFrequency(), which returns the number of ticks per second.

Example:

#include <stdio.h> #include <windows.h>                // for Windows APIs  int main(void) {     LARGE_INTEGER frequency;        // ticks per second     LARGE_INTEGER t1, t2;           // ticks     double elapsedTime;      // get ticks per second     QueryPerformanceFrequency(&frequency);      // start timer     QueryPerformanceCounter(&t1);      // do something     // ...      // stop timer     QueryPerformanceCounter(&t2);      // compute and print the elapsed time in millisec     elapsedTime = (t2.QuadPart - t1.QuadPart) * 1000.0 / frequency.QuadPart;     printf("%f ms.\n", elapsedTime); } 

Linux, Unix, and Mac

For Unix or Linux based system, you can use gettimeofday(). This function is declared in "sys/time.h".

Example:

#include <stdio.h> #include <sys/time.h>                // for gettimeofday()  int main(void) {     struct timeval t1, t2;     double elapsedTime;      // start timer     gettimeofday(&t1, NULL);      // do something     // ...      // stop timer     gettimeofday(&t2, NULL);      // compute and print the elapsed time in millisec     elapsedTime = (t2.tv_sec - t1.tv_sec) * 1000.0;      // sec to ms     elapsedTime += (t2.tv_usec - t1.tv_usec) / 1000.0;   // us to ms     printf("%f ms.\n", elapsedTime); }