CODEWITHSUNDEEP
c++parallel-processingopenmp
FvD
FvD

Reputation: 1375

OpenMP: Why are these omp parallel sections not executed with multiple threads?

I am trying to parallelize some code, but I am running into (presumably dumb) problems. The example code below returns "12", although I'd expect "21".

omp_get_max_threads() returns 8, omp_get_num_threads() returns 1 and omp_get_thread_num() returns 0 when I call them anywhere in this block. I guess I can conclude that it just gets executed by the master thread sequentially.

#include <omp.h>
#include <iostream>
#include <Windows.h>

using namespace std;

int main() {
    #pragma omp parallel sections num_threads(2) 
    {
        #pragma omp section 
            { Sleep(200);
              cout << "1"; }
        #pragma omp section 
            { cout << "2"; }
    }
}

What am I doing wrong? How can I force parallel processing of these sections?

For context: I am streaming data from two USB 3.0 cameras and calling the image from each sequentially is so slow that I am losing frames. I would like to basically set one thread aside for each camera to constantly demand its image.

This question has a similar title but didn't help. I'm using Visual Studio 2010.

Upvotes: 1

Views: 1532

Answers (1)

FvD
FvD

Reputation: 1375

The comments were correct: I forgot to set up OMP support in the project settings.

Remarkably, the number of frames I can transfer from the cameras dropped. Maximizing the bandwidth used is not as simple as that I suppose.

Upvotes: 1

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