problem with time function

Hey guys i am doing a basic swap program with generic pointers and I am trying to time it but I keep getting 0. Any idea why?

Code:

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 #include <iostream>
 #include <iomanip>
#include <ctime>
 using namespace std;

 void q(void *a, void *b, int n) {

clock_t c0, c1;

unsigned char *ca = (unsigned char *)a;
unsigned char *cb = (unsigned char *)b;
unsigned char c;

c0 = clock();


    for (int i = 0; i < n; i++) {
        c    = ca[i];
        ca[i] = cb[i];
        cb[i] = c;
    }

c1 = clock();

cout << "Process time is " <<
      (double)(c1-c0)/CLOCKS_PER_SEC
      << " secs" << endl;



 }

 int main() {

    int a = 4, b = 7;
    float x = 2.5f, y = 3.5f;

    q(&a, &b, sizeof(int));
    q(&x, &y, sizeof(float));

    cout << setprecision(1) << fixed;
    cout << "(a,b) = (" << a << ',' << b << ')' << endl;
    cout << "(x,y) = (" << x << ',' << y << ')' << endl;
 }

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Probably because what you are timing completes faster than the resolution of the timer :)

By the way, you should indent your code better ;)

is there anything i can change so i can get a time?

Well if you're on windows, then read QueryPerformanceCounter function (Windows)
Or state what machine/OS/Compiler you're using.

hey make your process to take more time for eg. put some sleep(2000) in for loop then you will get the time as 1.99999 like this...

Quote:

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Originally Posted by ushacy

hey make your process to take more time for eg. put some sleep(2000) in for loop then you will get the time as 1.99999 like this...

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Doesn't really solve his problem as the OP was looking to check how long it took for his sort to work.

Another good idea might to run the algorithm for X iterations and time it. Then divide your time with the number of iterations and voila - you get a result. An average even, which is better statistically than a single iteration.

basically what I want to do is take that swap function and make it happen 1000 times. I believe if I do that I should get a time value. I tried replacing n with 1000 but then it would just mess up the swap all together, so I have to keep sizeof.

Is there anyway I could make the swap happen 1000 times while still using the sizeof I am sending in?

Where did 1000 come from?

Elysia suggested this

Code:

---

- clock
-- for ( i = 0 ; i < 100000 ; i++ )
--- q(&a, &b, sizeof(int));
-- end for
- clock
- print time for 1M swaps of an int

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Move the clock code from the function under test and put it in main.