Compiling program on Beagle Board with Linux and profiling

sam33r said:

I am using gettimeofday function to calculate the time spent in doing particular part in program. Can someone please tell me how to convert this epoch time returned into microseconds?

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#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;
}

#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;
}

sam33r said:

Also I am using GPOF to do profiling. Are there any ways to improve the execution time of the program after doing the profiling.

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sam33r said:

I am using the function gettimeofday() to calculate time of execution of a certain function . I am running it 10000 times to get the mean, max and min values of execution time. the mean is expected but the max value is way greater then the mean execution time approximately 6-7 times the mean. Can you please tell me if there a specific reason fro this? Or it is just sporadic?

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bigdogguru said:

The variations in execution times could be the result of several factors, the most likely of which is pipelining, cache memory and other background/concurrent processes. The cache memory coupled with OS process switching can result in wide fluctuations in execution times.

Have you actually logged each execution time in a file after the 10,000 interations has completed?

BigDog

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bigdogguru said:

Where in relation to the other 9,999 execution times did this maximum execution time occur?

BigDog

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