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Processes

Every process is a separate instance of a particular program that is being run on a computer.

Threads

Threads are sets of instructions that get executed by the processes that contain them. The existence of multiple threads enables a process to separate work to be performed in parallel.

Debugging Single-threaded V.S. Multi-threaded Programs

Debugging usually occurs on a single threaded program by pausing the execution at a specific line of code. While the execution is paused, the values of all the variables can be inspected. This can be helpful to closely view what is occurring between each line of code.

Debugging a multithreaded program is different from debugging a single threaded program because each thread has its own sequence of execution, meaning that the point that the execution is paused at can vary for each thread.

OpenMP Debugging in Visual Studio

Debugging in Visual Studio will be demonstrated using this code:

#include <stdio.h>
#include <omp.h>

int main() {
	int numThreads = omp_get_max_threads();
	printf("Number of threads: %d\n", numThreads);
	#pragma omp parallel
	{
		int threadNum = omp_get_thread_num() + 1;
		printf("Hello thread #%d\n", threadNum);
	}
	printf("End of program");
}