CODEWITHSUNDEEP
c++openmp
lookingglass
lookingglass

Reputation: 39

openMP for loop Segmentation fault (core dumped)

I recently started learning openMP and I am trying to parallelize my code for convolution. Once I added #pragma to the for loop which is initializing the image array and there's no data dependency, the code broke and threw Segmentation fault (core dumped). I couldn't figure out what's wrong. Please help!

  // map values from original image to padded image
#pragma omp parallel for schedule(static)  
  for (size_t j = 0; j < n * n; j++) {
    size_t row = (j / n) + padding;
    size_t col = (j % n) + padding;
    size_t pos = (n + (padding * 2)) * row + col;
    padded_image[pos] = image[j];
  }

Upvotes: 0

Views: 506

Answers (1)

J&#233;r&#244;me Richard
J&#233;r&#244;me Richard

Reputation: 50278

The computed indices does not match with the allocated size. Indeed, the size of the allocated array padded_image does not depend on n while the accesses to the same in the targeted loop does. Regarding the loop, the size of the array should probably be: (n + (padding * 2)) * (n + (padding * 2)).

Please note that padded_image is not deleted. Moreover, modulus are very slow, please consider using two loops with an OpenMP clause collapse(2).

Upvotes: 1

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