asked on

Time Elapsed

I have this code that will return in seconds between starting of the program and the time when I do a RETURN.

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main(void)
{
      time_t timer1, timer2;

      time(&timer1);
      fflush(stdin);
      getchar();

      time(&timer2);

      printf("%lf", difftime(timer2, timer1));

      return EXIT_SUCCESS;
}

I wish to return in actual millisecond. How to do that?

AlexFM

difftime returns the elapsed time in seconds.

printf("%lf", (long)((difftime(timer2, timer1))*1000.0));

ASKER CERTIFIED SOLUTION

mnashadka

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mnashadka

Sorry, that was sort of C++ style; move the variable declarations to the top of the function.

cutie2000

ASKER

what header file do i need to include for the linux code?
i tried using time.h but cannot work

cutie2000

ASKER

ok i included stdlib.h and it solve the compilation error

cutie2000

ASKER

mnashadka, this is actually what I want.

int main()
{
...
int start, end;

start = getMilliSec();

//do some processing

end = getMilliSec();

printf("Diff in milli = %d\n", b-a);

}

int getMilliSec()
{
....
}

I am unable to modify your code to do the above.
Please help

cutie2000

ASKER

Just wanna ask.
I have this code.
Am I returning the correct value?
Can someone test it out for me?

I wish to get CPU usage from the for loop in millisec.
Are my functions doing fine?

#include <stdio.h>
#include <time.h>
#include <math.h>

clock_t get_clock();
float clock_diff(clock_t c1, clock_t c2);

int main() {
      int i;
      double dummy;
      float clk_diff;
      clock_t begin, end;

      printf("\tperform some computation...\n");
      begin = get_clock();
      for ( i=0; i<10000001; i++ ) {
            dummy=i-1.0/sqrt(i);
      }
      end = get_clock();
      printf("\tcomputation done\n");

      clk_diff = clock_diff(begin, end);
      printf("Time take for computation: %f\n", clk_diff);

      return 0;
}

/* get current CPU clock time */
clock_t get_clock() {
      return clock();
}

/* get CPU clock difference */
float clock_diff(clock_t c1, clock_t c2) {
      return (float)((c2-c1)/CLOCKS_PER_SEC);
}

Please reply.
Thanks in advance

cutie2000

ASKER

Do I have to do this?
return (float)((c2-c1)/CLOCKS_PER_SEC/1000);

mnashadka

My example does give you the milliseconds that are different. I think that's the best way to go, since if you do it in milliseconds and store it in an int or long, it's possible to go out of range of an int or long. Of course, you could use an unsigned long long. But to convert it to milliseconds, it would look like:

int milliseconds = (end.tv_usec / 1000) + (end.tv_sec * 1000);

Good luck.

Ajar

#include <sys/timeb.h>
int main(void)
{
struct timeb t1,t2;
ftime (&t1);
fflush(stdin);
getchar();
ftime (&t2);
printf("MILLISECONDS ELAPSED ARE %d\n", (t2.time +1000*t2.millitm) -(t1.time +1000*t1.millitm));
return EXIT_SUCCESS;
}

mnashadka

From the man pages of ftime:
BUGS
This function is obsolete. Don't use it. If the time in seconds suf-
fices, time(2) can be used; gettimeofday(2) gives microseconds;
clock_gettime(3) gives nanoseconds but is not yet widely available.