Copying memory allocated by cudaMallocPitch

Question

Can cudaMemcpy be used for memory allocated with cudaMallocPitch? If not, can you tell, which function should be used. cudaMallocPitch returns linear memory, so I suppose that cudaMemcpy should be used.

Answer 1

You certainly could use cudaMemcpy to copy pitched device memory, but it would be more usual to use cudaMemcpy2D. An example of a pitched copy from host to device would look something like this:

#include "cuda.h"
#include <assert.h>

typedef float real;

int main(void)
{

    cudaFree(0); // Establish context

    // Host array dimensions
    const size_t dx = 300, dy = 300; 

    // For the CUDA API width and pitch are specified in bytes
    size_t width = dx * sizeof(real), height = dy;

    // Host array allocation
    real * host = new real[dx * dy];
    size_t pitch1 = dx * sizeof(real);

    // Device array allocation
    // pitch is determined by the API call
    real * device;
    size_t pitch2;
    assert( cudaMallocPitch((real **)&device, &pitch2, width, height) == cudaSuccess );

    // Sample memory copy - note source and destination pitches can be different
    assert( cudaMemcpy2D(device, pitch2, host, pitch1, width, height, cudaMemcpyHostToDevice) == cudaSuccess );

    // Destroy context
    assert( cudaDeviceReset() == cudaSuccess );

    return 0;
}

(note: untested, cavaet emptor and all that.....)