Overflowing int's in OpenMP

Question

I'm trying my hand at writing a naive indexOf function. It currently works and gets the right position. However it overflows when counting the number of comparisons. I've tried converting them all to long long ints but it doesnt seem to be making any difference. What can I do to fix this?

int hostMatch(long long int *comparisons)
{
    long int i,j,k, lastI;

    i=0;
    j=0;
    k=0;
    lastI = textLength-patternLength;
    *comparisons=0;

    int lastIi = lastI+1;
    int position = -1;

    int numberThreads = 1;
    int totalCom = 0;

    #pragma omp parallel for default(none) num_threads(numberThreads) \
        shared(totalCom, position) \
        private(i,j,k) \
        firstprivate(lastIi,patternLength, textData, patternData)
    for (i=0;i<lastIi;i++)
    {
        if (position != -1)
        {
            // found
        }
        else
        {
            k=i;
            long long int count = 0L;
            for (j=0;j<patternLength;j++)
            {
                count++;
                if (textData[k] == patternData[j])
                {
                    if (j == patternLength - 1)
                    {
                        // found
                        position = i;
                    }
                }
                else
                {
                    break;
                }
                k++;
            }
            #pragma omp critical (totalLock)
            {
                totalCom += count;
            }
        }
    }
    /* END OF PARALLEL SECTION*/
    printf("Total Comparisons = %i\n", totalCom);
    (*comparisons) = totalCom;
    return position;
}

Answer 1

The totalCom variable is an int; that is more likely to be causing the overflow. Also, you don't need #pragma omp critical to update totalCom; add reduction(+ : totalCom) into your parallel for header instead.