Programming

I have a bottleneck in one of my applications...I have a loop that goes through a few thousand interations, but does quite a few things (digs info out of a database, sends the data to another application, etc...). I want to put in some debugging to determine what function calls are taking the most time to execute. I thought about marking times with the time() function, but that only gives a measurment in seconds. Are there any functions that can give more precise measurments (maybe milliseconds)?

use clock()

that would return in microseconds precision,

Code:

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

int main()
{
  int i;
  clock_t time_start;
  clock_t time_end;
  time_start=clock();
  for(i=0; i<100000; i++);
  time_end=clock();
  fprintf(stderr, "DIFF: %ld microseconds\n", time_end - time_start);
  return 0;
}
~

Thanks! I think that will do it.

clock() has a problem depending on the implementation. The granularity of the result is only guaranteed to be per second by the C99 standard. It can be finer. You can certainly try it.

gettimeofday returns the timeval struct which does have better resolution guranteed.

Do you know about cc -g -p myfile.c - o myfile ? profiling
You can then run your code, then look at the profiling output. gprof or prof will do this for you. It gives total times and number of calls for each function.

i accept the point with respect to the granularity of the clock command
(time resolution is only .01 second )
but it is ANSI standard and it is easily portable

on the other, gettimeofday() applicable to SVr4 and BSD4.3 standards,
so most likely it should support other versions.
and one main drawback is lesser OS donot support it...

Use GNU tools like gprof/gcov to analyse ur program.

John Arackal

You might want to sleep() at the end of each iteration to lower a bit cpu load and observer if the bottleneck is still there ...