C++/CUDA equation printing negative for 2 positives

Question

I am currently trying to run this equation with a ton of different inputs (x+y)^2 / xy

I have noticed an issue when i get x = 46340 and y = 1

It seems to output -46341 as seen here.

__global__ void proof() {
    int x = 1;
    int y = 1;
    int multi_number = 100000;

    bool logged = false;

    while (true) {
        long eq = ((x + y) * (x + y)) / (x * y);

        if (x >= multi_number) {
            x = 1;
            y = y + 1;
        }

        if (eq < 4) {
            if (logged == true) {
                continue;
            }
            printf("\nGPU: Equation being used: (%d", x);
            printf("+%d", y);
            printf(")^2 / %d", x);
            printf("*%d", y);
            printf(" >= 4");
            printf("\nGPU: Proof Failed: %d", x);
            printf(", %d", y);
            logged = true;
            continue;
        }

        if (y >= multi_number) {
            if (x >= multi_number) {
                if (logged == true) {
                    continue;
                }
                printf("\nGPU: Proof is true for all cases.");
                logged = true;
                continue;
            }
        }

        printf("\nGPU: Equation being used: (%d", x);
        printf("+%d", y);
        printf(")^2 / %d", x);
        printf("*%d", y);
        printf(" >= 4");
        printf("\nGPU: %d", eq); // printing the equation

        x = x + 1;
    }
}

I have tried rewriting the equation and even putting the equation into a calculator. The calculator always gave a different response than the code is currently outputting, I have since double checked what I have put into the calculator and it remains the same.

I was expecting an output of 46342.

Overflow of `int`. You may wish to study how type handling occurs during arithmetic in c++. This is almost certainly a duplicate. — Robert Crovella, Dec 12 '22 at 21:05

Box · Accepted Answer · 2022-12-23T22:35:02.137

-3

int overflow, used longs instead to fix the issue.

edited Dec 23 '22 at 22:35

answered Dec 12 '22 at 21:23

Box

1
4

C++/CUDA equation printing negative for 2 positives

1 Answers1