exercise3

Lecture 4 - Exercise 3

Problem

int size = N * sizeof(float);
int wsize = (2 * RADIUS + 1) * sizeof(float);

...

float *d_weights; cudaMalloc(&d_weights, wsize);
float *d_in; cudaMalloc(&d_in, wsize);
float *d_out; cudaMalloc(&d_out, wsize);

cudaMemcpy(d_weights, weights, wsize, cudaMemcpyHostToDevice);
cudaMemcpy(d_in, in, wsize, cudaMemcpyHostToDevice);

...

cudaMemcpy(out, d_out, wsize, cudaMemcpyDeviceToHost);

Input and output arrays are allocated with the wrong size. The input and output arrays should be allocated with the size N * sizeof(float), while the weights array should be allocated with the size (2 * RADIUS + 1) * sizeof(float). Therefore wsize should be interchanged with size in the cudaMalloc and cudaMemcpy calls.

Solution

int size = N * sizeof(float);
int wsize = (2 * RADIUS + 1) * sizeof(float);

...

float *d_weights; cudaMalloc(&d_weights, wsize);
float *d_in; cudaMalloc(&d_in, size);
float *d_out; cudaMalloc(&d_out, size);

cudaMemcpy(d_weights, weights, wsize, cudaMemcpyHostToDevice);
cudaMemcpy(d_in, in, size, cudaMemcpyHostToDevice);

...

cudaMemcpy(out, d_out, size, cudaMemcpyDeviceToHost);