I am using OpenMP to do multithreading with my nested loops. Since new to this stuff, I am not sure if I am using OpenMP in the correct way so that it can actually do the parallel programming. So I like to know if I can measure the performance of my C++ program that uses OpenMP so I can tell it actually works and I am on the right track? Like how many threads are running in parallel and how long it takes for each of them to finish. Thanks and regards!
#include <omp.h>
...
int target_thread_num = 4;
omp_set_num_threads(target_thread_num);
unsigned long times[target_thread_num];
// Initialize all the times
#pragma omp parallel
{
int thread_id = omp_get_thread_num();
times[thread_id] = start_time();
std::cout << "Thread number: " << omp_get_thread_num() << endl;
times[thread_id] = end_time();
}
...
Obviously you need ot provide the two timer functions, but that's the gist. The OMP functions are pretty self-explanatory. Also make sure that your environment is set up properly and that you're compiling with the proper mechanisms. g++ option is -fopenmp. On Visual Studio go to project settings, C++, Language, and enable "OpenMP Support".
You could use windows taskmanager (CTRL-SHIFT-ESC) on windows to monitor CPU usage, or top on *nix boxes.
Just check if many cores are used or not
You can use your debugger (Visual Studio if you're on Windows) to:
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