CODEWITHSUNDEEP
cruntimeclock
zakparks31191
zakparks31191

Reputation: 937

Finding the runtime of a segment of code in C

The below code should find the runtime in seconds of the for loop. Looking at other resources this should do the trick, having an initial clock() subracted from a clock() after the for loop runs. Any ideas why the code isn't working as written?

#include <stdio.h>
#include <time.h>

//prototypes
int rfact(int n);
int temp = 0;

main()
{
    int n = 0;
    int i = 0;
    double result = 0.0;
    clock_t t;
    printf("Enter a value for n: ");
    scanf("%i", &n);

    printf("n=%i\n", n);

    //get current time
    t = clock();

    //process factorial 2 million times
    for(i=0; i<2000000; i++)
    {
        rfact(n);
    }

    printf("n=%i\n", n);

    //get total time spent in the loop
    result = (double)((clock() - t)/CLOCKS_PER_SEC);

    //print result
    printf("runtime=%d\n", result);
}

//factorial calculation
int rfact(int n)
{

    if (n<=0)
    {
        return 1;
    }
    return n * rfact(n-1);
}

Upvotes: 0

Views: 272

Answers (1)

David Schwartz
David Schwartz

Reputation: 182829

result = (double)((clock() - t)/CLOCKS_PER_SEC);

This should be:

result = ((double)(clock() - t))/CLOCKS_PER_SEC;

Otherwise, you're doing integer division and converting the result to a double, which is not what you want.

Also:

printf("runtime=%d\n", result);

Should be:

printf("runtime=%f\n", result);

Upvotes: 2

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