Visual Studio 2013 OMP release mode

Question

I'm trying to use OpenMP in Visual Studio 2013.

It's working very well in Debug Mode and there is a huge performance boost, however when I switch to Release Mode I get worst results with OpenMP activated.

Printing thread number will give always 0 in Release Mode.

  printf("%d\n", omp_get_thread_num());

So obviously my question is: Does OpenMP works in Release Mode? There is already a question on StackOverlfow but nobody answered

Answer 1

I've made a little test with MSVC2013 Community Edition and it works perfectly also in release.

The probable cause of your problem is that some compiling options are dependent of the chosen build mode. So if you set some options like /openmp while in the debug mode, you have to make sure to set them again, once you've switched to release mode:

And here the small test to show that it works:

const int size = 2048;
double mytable[size];
std::map<int, int> t;

#pragma omp parallel for   
for(int n = 0; n < size; ++n) {
    double angle = 2 * 3.1415 * n / size; 
    mytable[n] = std::sin(angle) - std::pow(std::cos(angle), 2.0);
    t[omp_get_thread_num()]++; 
}
std::cout << "Number of elements processed per thread:"<<std::endl; 
for(auto &x : t)
    std::cout<< x.first<<": "<< x.second<<std::endl; 
std::cout << "Done" << std::endl;