Question

(This is NOT a homework help question)

I was asked by my professor to write a simple program for computing the dot product of two linear arrays. That was the easy part, so I thought. When I build and run the program in NetBeans IDE 7.0, my print statement at the end of the function reads:

The dot product is 1246

RUN FAILED (exit value 25, total time: 68ms)

But when I run it in debug mode, my output window shows:

The dot product is 1240

This program serves as a precursor to two other programs I must build on top of it (using Pthreads and OpenMP), so it’s important to me that I get it working correctly and I don’t have any surprise outcomes.

Any help would be appreciated. I just don’t get why this is happening. Everything looks right to me but a new pair of eyes wouldn’t hurt.

#include <stdio.h>
#include <stdlib.h>

#define NN 16  //Len of array

main()
{
    int a[NN], b[NN], iVal, dPro;
    int i;
    iVal = 0;
    for(i=0; i<NN; i++) //Loop for building the arrays
    {
        a[i]=1.0*(i);
        b[i]=1.0*(i);
    }
    for(i=0; i<NN; i++) //Loop for computing the dot product
    {
        dPro += a[i]*b[i];
    }

    printf("The dot product is %d \n", dPro);

}

Answer 1

You add values to dPro, but you never set its start value.