What is OpenMP?

What is OpenMP? Let's check the definition from its official FAQ:

OpenMP is a specification for a set of compiler directives, library routines, and environment variables that can be used to specify high-level parallelism in Fortran and C/C++ programs.

The following defintion is from Wikipedia:

OpenMP (Open Multi-Processing) is an application programming interface (API) that supports multi-platform shared memory multiprocessing programming in C, C++, and Fortran, on most platforms, instruction set architectures and operating systems, including Solaris, AIX, HP-UX, Linux, macOS, and Windows. It consists of a set of compiler directives, library routines, and environment variables that influence run-time behavior.

To summarize, OpenMP defines a standard API which supports multi-thread programming on many different Operating Systems and CPU architectures. Now it can be used in 3 programming languages: C, C++ and Fortran. The OpenMP API consists of compiler directives(C/C++ begin with #pragma omp, and Fortran begins with !$omp), library routines, and environment variables.

So for applications who uses OpenMP, OpenMP hides the details of thread management, such as creating, joining, scheduling threads, etc. The applications should concentrate on the code logic, and this will save a lot of energy from developers.