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Using cudaMalloc to highlight a matrix

I use cudaMalloc and cudaMemcpy to select a matrix and copy arrays of vectors into it, for example:

float **pa;    
cudaMalloc((void***)&pa,  N*sizeof(float*)); //this seems to be ok
for(i=0; i<N; i++) {
    cudaMalloc((void**) &(pa[i]), N*sizeof(float)); //this gives seg fault
    cudaMemcpy (pa[i], A[i], N*sizeof(float), cudaMemcpyHostToDevice); // also i am not sure about this
}

What is wrong with my instructions? thanks in advance

PS A [i] - vector

Now I'm trying to copy the matrix from the device to the matrix from the host:

Suppose I have ** pc in the device and ** pgpu is in the host:

cudaMemcpy (pgpu, pc, N*sizeof(float*), cudaMemcpyDeviceToHost);
for (i=0; i<N; i++)
    cudaMemcpy(pgpu[i], pc[i], N*sizeof(float), cudaMemcpyDeviceToHost);

= wrong ....

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2 answers

pais in the device’s memory, so it &(pa[i])doesn’t do what you expect from it. It will work

float **pa;
float **pah = (float **)malloc(pah, N * sizeof(float *));    
cudaMalloc((void***)&pa,  N*sizeof(float*));
for(i=0; i<N; i++) {
    cudaMalloc((void**) &(pah[i]), N*sizeof(float));
    cudaMemcpy (pah[i], A[i], N*sizeof(float), cudaMemcpyHostToDevice);
}
cudaMemcpy (pa, pah, N*sizeof(float *), cudaMemcpyHostToDevice);

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, .

+5

? , , pa 1- . - :

float *pa;
cudaMalloc((void**)&pa, N*N*sizeof(float));

, A [i], , .

+2

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