Linux ? Windows?? ???? ? ??? ?? ??? ???? ??

????? CPU? ??? ?? ??? ???? ?? ?????. ?? ???? ??. x86 ? x86_64 ????? ?? ???? Linux ? Windows?? ?? ???? ??? ??? ????.

?? ?? ? ??? ?? ??

???? ??? CPU ??? ????? ?? ? ???? ? ??? ??? ??? ????? ?? ??? ?????.

int startcputime, endcputime, wcts, wcte;

startcputime = cputime();
function(args);
endcputime = cputime();

std::cout << "it took " << endcputime - startcputime << " s of CPU to execute this\n";

wcts = wallclocktime();
function(args);
wcte = wallclocktime();

std::cout << "it took " << wcte - wcts << " s of real time to execute this\n";

??? ??? ????

??? ?? ?? ?? ??? ???? ??????. , ?? ??? ???? ?????? ???? ??? ??? ??? ? ??? ?????.

??

??? C? C ???? Windows ? Linux?? ???? ??? ??????.

//  Windows
#ifdef _WIN32
#include <Windows.h>
double get_wall_time(){
    LARGE_INTEGER time, freq;
    if (!QueryPerformanceFrequency(&freq)){
        //  Handle error
        return 0;
    }
    if (!QueryPerformanceCounter(&time)){
        //  Handle error
        return 0;
    }
    return (double)time.QuadPart / freq.QuadPart;
}
double get_cpu_time(){
    FILETIME a, b, c, d;
    if (GetProcessTimes(GetCurrentProcess(), &a, &b, &c, &d) != 0){
        //  Returns total user time.
        //  Can be tweaked to include kernel times as well.
        return
            (double)(d.dwLowDateTime |
            ((unsigned long long)d.dwHighDateTime << 32)) * 0.0000001;
    }else{
        //  Handle error
        return 0;
    }
}

//  Linux
#else
#include <time.h>
#include <sys/time.h>
double get_wall_time(){
    struct timeval time;
    if (gettimeofday(&time, NULL)){
        //  Handle error
        return 0;
    }
    return (double)time.tv_sec + (double)time.tv_usec * .000001;
}
double get_cpu_time(){
    return (double)clock() / CLOCKS_PER_SEC;
}
#endif

?? ??? ??:

• Windows:

  • ? ??: ?? ???
  • CPU ??: GetProcessTimes()

• Linux:

  • ? ??: gettimeofday()
  • CPU ??: clock()

??

??? ??? ???? ??? ????.

#include <math.h>
#include <iostream>
using namespace std;

int main(){

    //  Start Timers
    double wall0 = get_wall_time();
    double cpu0 = get_cpu_time();

    //  Computational task (e.g., numerical summation).
    double sum = 0;
#pragma omp parallel for reduction(+ : sum)
    for (long long i = 1; i < 10000000000; i++){
        sum += log((double)i);
    }

    //  Stop timers
    double wall1 = get_wall_time();
    double cpu1 = get_cpu_time();

    cout << "Wall Time = " << wall1 - wall0 << endl;
    cout << "CPU Time = " << cpu1 - cpu0 << endl;

    //  Prevent code elimination (optimization).
    cout << endl;
    cout << "Sum = " << sum << endl;
}

? ?? ??? ?? ?? ?? ???? CPU ??? ?????.

? ??? Linux ? Windows?? ???? ? ??? ?? ??? ???? ??? ??????? ?? ?????. ??? ??? PHP ??? ????? ?? ?? ??? ?????!