How does OpenMP handle nested loops?

Question

Does the following code just parallelize the first (outer) loops, or it parallelize the entire nested loops?

    #pragma omp parallel for
    for (int i=0;i&         


        

Answer 1

The lines you have written will parallelize only the outer loop. To parallelize both you need to add a collapse clause:

#pragma omp parallel for collapse(2)
    for (int i=0;i

You may want to check OpenMP 3.1 specifications (sec 2.5.1) for more details.