openmp - OpenGenus IQ: Computing Expertise & Legacy

[Fixed] undefined reference to omp_get_max_threads / omp_get_thread_num

In this article, we have presented the fix for the OpenMP error undefined reference to omp_get_max_threads / omp_get_thread_num / omp_get_num_threads. The issue is with the compilation command.

C++

#pragma omp master [explained with example]

In this article, we have explained the concept of #pragma omp master, when it is used and compared omp master with omp single.

C++

#pragma omp single [explained with example]

In this article, we have explained the concept of #pragma omp single, when it is used and compared omp single with omp critical and omp master.

C++

#pragma omp parallel [explained with example]

In this article, we have explored the concept of the OpenMP directive #pragma omp parallel along with C++ code examples.

C++

#pragma omp parallel for

In this article, we have explained the concept behind `#`pragma omp parallel and presented the idea with C++ code examples. We have explained how it is different from pragma omp parallel and pragma omp for.

C++

#pragma omp critical [explained with example]

In this article, we have explained the concept of #pragma omp critical with a C++ code example, when it is used and the difference between omp critical and omp single and atomic.

Software Engineering

Get introduced to using OpenMP to parallelize a C++ code

In this article, we will take a look at some of the basic ways we can use OpenMP to parallelize a C++ code. OpenMP is a feature of the compiler like GCC

openmp

Install OpenMP from source

In this guide, we will walk you through the installation steps of OpenMP from source. Open Multi-Processing is a library that is used to make programs execute in a parallel fashion. It supports multi-platform shared memory multiprocessing programming in C, C++, and Fortran on most platforms

openmp

OpenMP clauses: firstprivate, lastprivate, ordered

There are three basic OpenMP clauses namely firstprivate, lastprivate and ordered. firstprivate clause is used to initialize a variable from the serial part of the code and private clause doesn't initialize the variable

openmp

Basic OpenMP functions

There are 3 basic functions in OpenMP namely omp_get_thread_num, omp_set_num_threads (nthreads) and omp_get_num_threads. We have given a basic C/ C++ example to demonstrate the use of the function and the observation of the output as well

openmp

When to use OpenMP directives?

If some section of your code can be parallelized and you have more than one processor, you should definitely speed up the execution of your program using OpenMP directives. We have demonstrated how to use Amdahl's law to calculate the expected speed up and profiling to find which section takes time

openmp

Introduction to OpenMP

OpenMP is an open source library which is used for multi-threaded parallel processing and shared-memory multi-processor (core) computers. In OpenMP, part of program is a single thread and part is multi-threaded We have given advantages, disadvantages, industry use example, approach of OpenMP library