OpenMP | Hello World program

Here is a simple “Hello World” program using OpenMP in C:

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

int main() {
    #pragma omp parallel
    {
        printf("Hello, World! from thread %d\n", omp_get_thread_num());
    }
    return 0;
}

Explanation:

1. #include <omp.h>: This header file is required to use OpenMP functions and directives.
2. #pragma omp parallel: This directive tells the compiler to parallelize the following block of code. Multiple threads will execute the block concurrently.
3. omp_get_thread_num(): This function returns the thread number (ID) of the current thread.

Compilation:

To compile this program, use an OpenMP-compatible compiler like gcc with the -fopenmp flag:

gcc -fopenmp hello_world.c -o hello_world

Execution:

When you run the program:

./hello_world

It will print “Hello, World!” from multiple threads, with each thread displaying its thread ID.

Example Output:

Hello, World! from thread 0
Hello, World! from thread 1
Hello, World! from thread 2
Hello, World! from thread 3

The output order may vary depending on how the threads are scheduled by the system.