C++ Time Calculation – Efficient Methods and Examples

c++

I know this question has been asked few times over SO but none of them is really helping me out, so asking again.

I am using windows xp and running visual studio c++ 2008.

All the code which i am looking is using time.h but i think may be its not working correctly here, because results are making me suspicious.

So this is what i want.

star time = get time some how (this is my question)

my code

end time = get time some how (this is my question)

time passed = start time - end time

Best Answer

Here is what I use to print time in milliseconds.

void StartTimer( _int64 *pt1 )
{
   QueryPerformanceCounter( (LARGE_INTEGER*)pt1 );
}

double StopTimer( _int64 t1 )
{
   _int64 t2, ldFreq;

   QueryPerformanceCounter( (LARGE_INTEGER*)&t2 );
   QueryPerformanceFrequency( (LARGE_INTEGER*)&ldFreq );
   return ((double)( t2 - t1 ) / (double)ldFreq) * 1000.0;
}

Use it like this:

    _int64 t1;

    StartTimer( &t1 );

    // do some stuff

    printf( "Time = %.3f\n", StopTimer( t1 ));

Related Solutions

C++ – How to Calculate Time Difference

See std::clock() function.

const clock_t begin_time = clock();
// do something
std::cout << float( clock () - begin_time ) /  CLOCKS_PER_SEC;

If you want calculate execution time for self ( not for user ), it is better to do this in clock ticks ( not seconds ).

EDIT:
responsible header files - <ctime> or <time.h>

C++ Execution Time – How to Calculate?

If you have cygwin installed, from it's bash shell, run your executable, say MyProgram, using the time utility, like so:

/usr/bin/time ./MyProgram

This will report how long the execution of your program took -- the output would look something like the following:

real    0m0.792s
user    0m0.046s
sys     0m0.218s

You could also manually modify your C program to instrument it using the clock() library function, like so:

#include <time.h>
int main(void) {
    clock_t tStart = clock();
    /* Do your stuff here */
    printf("Time taken: %.2fs\n", (double)(clock() - tStart)/CLOCKS_PER_SEC);
    return 0;
}

Best Answer

Related Solutions

C++ – How to Calculate Time Difference

C++ Execution Time – How to Calculate?

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