Estimate time of execution c-function execution

[CodingStyle]

Hello all! I need help. I need to estimate function execution time in under Linux OS. I guess that it's right way to estimate code/algorithm performance. I'm trying, something like this:

#include #include #include void test(){
int i;int s=0;

for(i=1; i<1000000; i++){s+=sin(i)/i;}

}
float timedifference_msec(struct timeval t0, struct timeval t1)
{
return (t1.tv_sec - t0.tv_sec) * 1000.0f + (t1.tv_usec - t0.tv_usec) / 1000.0f;
}

int main(void)
{
struct timeval t0;
struct timeval t1;
float elapsed;
gettimeofday(&t0, 0);
f1();
gettimeofday(&t1, 0);
elapsed = timedifference_msec(t0, t1);
printf("Code executed in %f milliseconds.\n", elapsed);
return 0;
}

. But It's wall clock, I'm not sure that I can estimate performance by this way, besides, I need approach which will allow to measure time of each function which I choose. I've heard that there is approach to use CPU-time.

[Lost User]

CodingStyle wrote:

I've heard that there is approach to use CPU-time.

And there is even a man page[^] for it.

[Jochen Arndt]

For high accuray difference time measurements with Linux use clock_gettime[^] with timer ID CLOCK_MONOTONIC or CLOCK_PROCESS_CPUTIME_ID. This requires including time.h and linking with the real time library librt (link option -lrt). An example can be found at http://www.guyrutenberg.com/2007/09/22/profiling-code-using-clock_gettime/[^].

[Dr Fry]

Yeah. There is such approach like, count the number of ticks to estimate performance. I do not think that it's panacea. Richard MacCutchan and Jochen Arndt also correct. But I guess that you mean universal and independent implementation version. Look here.

[CodingStyle]

Thank you!

[Arthur V Ratz]

This is probably what you need:

#include <time.h>
#include <sys/time.h>
#include <stdio.h>
void test(){
int i;int s=0;

for(i=1; i<1000000; i++){s+=sin(i)/i;}

}

int main(void)
{
clock_t time[2], timediff;
float elapsed;
time[0] = clock();
f1();
time[1] = clock();
elapsed = ((float)abs(time[0] - time[1]))/CLOCKS_PER_SEC;
printf("Code executed in %f milliseconds.\n", elapsed);
return 0;
}