Calculate Execution Time in C ?

[infantheartlyje]

How to calculate Execution time in milliseconds?
if i use time() function i can get the result only in seconds .
What about clock function ? How to print the difference using clock_t variable?

ts=clock();
quicksort(x,0,size-1);
printf("Time elapsed: %f\n", ((double)clock() - ts) / CLOCKS_PER_SEC);

its only resulting in Seconds .

 

[bigdogguru]

To convert the Epoch into microseconds you must add both members of the structure, by first converting seconds contained in timeval.tv_sec and adding timeval.tv_usec both contained in the timeval structure.

For wall-clock time:

#include <sys/time.h>
#include <iostream>

int main(int argc, char **argv) {
    // ProcessTime example
    struct timeval startTime;
    struct timeval endTime;
    // get the current time
    // - NULL because we don't care about time zone
    gettimeofday(&startTime, NULL);
    // algorithm goes here
    what_you_want_to_time();
    // get the end time
    gettimeofday(&endTime, NULL);
    // calculate time in microseconds
    double tS = startTime.tv_sec*1000000 + (startTime.tv_usec);
    double tE = endTime.tv_sec*1000000  + (endTime.tv_usec);
    std::cout << "Total Time Taken: " << tE - tS << std::endl;
    return 0;
}

For process time:

#include <sys/time.h>
#include <iostream>
int main(int argc, char **argv) {
    // ProcessTime example
    struct timeval startTime;
    struct timeval endTime;
    //structure for rusage
    struct rusage ru;
    // get the current time
    // - RUSAGE_SELF for current process
    // - RUSAGE_CHILDREN for *terminated* subprocesses
    getrusage(RUSAGE_SELF, &ru);
    startTime = ru.ru_utime;
    // algorithm goes here
    what_you_want_to_time();
    // get the end time
    getrusage(RUSAGE_SELF, &ru);
    endTime = ru.ru_utime;
    // calculate time in microseconds
    double tS = startTime.tv_sec*1000000 + (startTime.tv_usec);
    double tE = endTime.tv_sec*1000000  + (endTime.tv_usec);
    std::cout << "Total Time Taken: " << tE - tS << std::endl;
    return 0;
}

Hope the info helps,

BigDog

 

[infantheartlyje]

For process time:

#include <sys/time.h>
#include <iostream>
int main(int argc, char **argv) {
    // ProcessTime example
    struct timeval startTime;
    struct timeval endTime;
    //structure for rusage
    struct rusage ru;
    // get the current time
    // - RUSAGE_SELF for current process
    // - RUSAGE_CHILDREN for *terminated* subprocesses
    getrusage(RUSAGE_SELF, &ru);
    startTime = ru.ru_utime;
    // algorithm goes here
    what_you_want_to_time();
    // get the end time
    getrusage(RUSAGE_SELF, &ru);
    endTime = ru.ru_utime;
    // calculate time in microseconds
    double tS = startTime.tv_sec*1000000 + (startTime.tv_usec);
    double tE = endTime.tv_sec*1000000  + (endTime.tv_usec);
    std::cout << "Total Time Taken: " << tE - tS << std::endl;
    return 0;
}

Hope the info helps,

BigDog

Am using C in GCC compiler . Not C++.
After compiling this program i got these errors.

qstchk1.c: In function ‘main’:
qstchk1.c:10:15: error: storage size of ‘ru’ isn’t known
qstchk1.c:18:11: error: ‘RUSAGE_SELF’ undeclared (first use in this function)
qstchk1.c:18:11: note: each undeclared identifier is reported only once for each function it appears in

 

[bigdogguru]

Am using C in GCC compiler . Not C++.

The only C++ features in the code are the <iostream> routines. Substitute your own "printf()" for the "cout" statements.

After compiling this program i got these errors.

qstchk1.c: In function ‘main’:
qstchk1.c:10:15: error: storage size of ‘ru’ isn’t known
qstchk1.c:18:11: error: ‘RUSAGE_SELF’ undeclared (first use in this function)
qstchk1.c:18:11: note: each undeclared identifier is reported only once for each function it appears in

Try adding the following header file:

#include <sys/resource.h>

The structure "rusage" is contained within "resource.h" on some systems.


BigDog