Question

If I try to send to my CUDA device a struct wich is heavier than the size of memory available, will CUDA give me any kind of warning or error?

I’m asking that because my GPU has 1024 MBytes (1073414144 bytes) Total amount of global memory, but I don’t know how I should handle and eventual problem.

That’s my code:

#define VECSIZE 2250000
#define WIDTH 1500
#define HEIGHT 1500



// Matrices are stored in row-major order:
// M(row, col) = *(M.elements + row * M.width + col)
struct Matrix
{

    int width;
    int height;
    int* elements;

};


   int main()
   {


Matrix M;
M.width = WIDTH;
M.height = HEIGHT;
M.elements = (int *) calloc(VECSIZE,sizeof(int));   

int row, col;   


// define Matrix M
// Matrix generator:
for (int i = 0; i < M.height; i++)
    for(int j = 0; j < M.width; j++)
    {
    row = i;
    col = j; 

    if (i == j)
    M.elements[row * M.width + col] = INFINITY;
        else
        {
        M.elements[row * M.width + col] = (rand() % 2); // because 'rand() % 1' just does not seems to work ta all.
        if (M.elements[row * M.width + col] == 0)  // can't have zero weight.
            M.elements[row * M.width + col] = INFINITY;
            else if (M.elements[row * M.width + col] == 2)
                M.elements[row * M.width + col] = 1;    

        }

    }





// Declare & send device Matrix to Device.
Matrix d_M;
d_M.width = M.width;
d_M.height = M.height;
size_t size = M.width * M.height * sizeof(int);
cudaMalloc(&d_M.elements, size);
cudaMemcpy(d_M.elements, M.elements, size, cudaMemcpyHostToDevice);

int *d_k=  (int*) malloc(sizeof(int));
cudaMalloc((void**) &d_k, sizeof (int));



int *d_width=(int*)malloc(sizeof(int));
cudaMalloc((void**) &d_width, sizeof(int));
unsigned int *width=(unsigned int*)malloc(sizeof(unsigned int));
width[0] = M.width;
cudaMemcpy(d_width, width, sizeof(int), cudaMemcpyHostToDevice);

int *d_height=(int*)malloc(sizeof(int));
cudaMalloc((void**) &d_height, sizeof(int));
unsigned int *height=(unsigned int*)malloc(sizeof(unsigned int));
height[0] = M.height;   
cudaMemcpy(d_height, height, sizeof(int), cudaMemcpyHostToDevice);
    /*

        et cetera .. */

Answer 1

While you may not currently be sending enough data to the GPU to max out it’s memory, when you do, your cudaMalloc will return the error code cudaErrorMemoryAllocation which as per the cuda api docs, signals that the memory allocation failed. I note that in your example code you are not checking the return values of the cuda calls. These return codes need to be checked to make sure your program is running correctly. The cuda api does not throw exceptions: you must check the return codes. See this article for info on checking the errors and getting meaningful messages about the errors