-1

Currently I'm trying to time a process to compare with a sample program I found online that used opencl. Yet when I try to time this process I'll get very strange values as shown below.

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <CL/cl.h>
#include <time.h>

int main(void) {

    int n = 100000;
    size_t bytes = n * sizeof(double);

    double *h_a;
    double *h_b;
    double *h_c;
    h_a = (double*)malloc(bytes);
    h_b = (double*)malloc(bytes);
    h_c = (double*)malloc(bytes);

    int i;
    for(i = 0; i < n; i++)
    {
        h_a[i] = sinf(i)*sinf(i);
        h_b[i] = cosf(i)*cosf(i);
    }

    clock_t start = clock();
    for(i = 0; i < n; i++)
        h_c[i] = h_a[i] + h_b[i];
    clock_t stop = clock();
    double time = (stop - start) / CLOCKS_PER_SEC;
    printf("Clocks per Second: %E\n", CLOCKS_PER_SEC);
    printf("Clocks Taken: %E\n", stop - start);
    printf("Time Taken: %E\n", time);

    free(h_a);
    free(h_b);
    free(h_c);

    system("PAUSE");
    return 0;
}

Results:

    C:\MinGW\Work>systesttime
    Clocks per Second: 1.788208E-307
    Clocks Taken: 1.788208E-307
    Time Taken: 0.000000E+000
    Press any key to continue . . .

Its giving very strange values for everything there. I understand that it must be around 1,000,000 and I don't know why its doing this. It used to give values around 6E+256 for everything which was equally concerning.

Matty Hooper
  • 11
  • 4
  • 1
    You can reduce your example code to `printf("Clocks per Second: %E\n", CLOCKS_PER_SEC);`, which will give you the warning **format '%E' expects argument of type 'double', but argument 2 has type 'long int' [-Werror=format=]**. http://ideone.com/EYeVvg – mch Jan 26 '17 at 10:01

1 Answers1

1

It looks like your clock_t is not double, so %E is the wrong format specifier.

It's probably long. Try this:

printf("Clocks per Second: %E\n", (double)CLOCKS_PER_SEC);
Ben
  • 34,935
  • 6
  • 74
  • 113