profiling code, linux, c99

gistfile1.txt

//gcc -std=c99 -Wall -Wextra -Wpedantic -Wshadow main.c

#define _POSIX_C_SOURCE 199309L
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h> //sleep();
#include <time.h>


void printTimeDiff(struct timespec *tm_start, struct timespec *tm_stop)
{
    long nanosec_diff = tm_stop->tv_nsec - tm_start->tv_nsec;

    if ( nanosec_diff < 0 )
    {
        printf( "%ld:%09ld\n", tm_stop->tv_sec - tm_start->tv_sec - 1 , 1000000000 + nanosec_diff );
    }
    else
    {
        printf( "%ld:%09ld\n", tm_stop->tv_sec - tm_start->tv_sec, nanosec_diff );
    }

}

/*

    CLOCK_REALTIME - system-wide realtime clock.
    CLOCK_PROCESS_CPUTIME_ID - high-resolution per-process timer from the CPU.
    CLOCK_THREAD_CPUTIME_ID - thread-specific CPU-time clock.

    struct timespec time_start, time_stop;

    clock_gettime(CLOCK_REALTIME, &time_start);

    ...
    code
    ...

    clock_gettime(CLOCK_REALTIME, &time_stop);

    printTimeDiff(&time_start, &time_stop);

*/

int main()
{

    //TEST

    struct timespec time_start, time_stop;

    printf("wait 1 sec\n");

    clock_gettime(CLOCK_REALTIME, &time_start);

    sleep(1);   //1 sec

    clock_gettime(CLOCK_REALTIME, &time_stop);

    printTimeDiff(&time_start, &time_stop);



    struct timespec nsleep_time;

    //1.2 sec
    nsleep_time.tv_sec = 1;
    nsleep_time.tv_nsec = 200000000;

    printf("wait 1.2 sec\n");

    clock_gettime(CLOCK_REALTIME, &time_start);

    nanosleep(&nsleep_time, NULL);

    clock_gettime(CLOCK_REALTIME, &time_stop);

    printTimeDiff(&time_start, &time_stop);



    nsleep_time.tv_sec = 0;
    nsleep_time.tv_nsec = 0;

    printf("twenty times +0.07 sec (CLOCK_REALTIME)\n");

    for (int i = 0; i < 20; ++i)
    {
        //just for testing
        long tmp = nsleep_time.tv_nsec + 70000000;

        if ( tmp >= 1000000000 )
        {
            nsleep_time.tv_sec += 1;
            nsleep_time.tv_nsec = tmp - 1000000000;
        }
        else
        {
            nsleep_time.tv_nsec = tmp;
        }

        clock_gettime(CLOCK_REALTIME, &time_start);

        nanosleep(&nsleep_time, NULL);

        clock_gettime(CLOCK_REALTIME, &time_stop);

        printTimeDiff(&time_start, &time_stop);

    }



    printf("CLOCK_PROCESS_CPUTIME_ID\n");

    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &time_start);

    nanosleep(&nsleep_time, NULL);

    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &time_stop);

    printTimeDiff(&time_start, &time_stop);


    return 0;
}