Compiling OpenMP Programs

All compilers installed on Anvil include OpenMP functionality for C, C++, and Fortran. An OpenMP program is a single process that takes advantage of a multi-core processor and its shared memory to achieve a form of parallel computing called multithreading. It distributes the work of a process over processor cores in a single compute node without the need for MPI communications.

OpenMP programs require including a header file:
Language	Header Files
Fortran 77	`INCLUDE 'omp_lib.h'`
Fortran 90	`use omp_lib`
Fortran 95	`use omp_lib`
C	`#include <omp.h>`
C++	`#include <omp.h>`

Sample programs illustrate task parallelism of OpenMP:

A sample program illustrates loop-level (data) parallelism of OpenMP:

omp_loop.c

To load a compiler, enter one of the following:

$ module load intel
$ module load gcc
$ module load aocc

The following table illustrates how to compile your shared-memory program. Any compiler flags accepted by ifort/icc compilers are compatible with OpenMP.
Language	Intel Compiler	GNU Compiler	AOCC Compiler
Fortran 77	`$ ifort -qopenmp myprogram.f -o myprogram`	`$ gfortran -fopenmp myprogram.f -o myprogram`	`$ flang -fopenmp program.f -o program`
Fortran 90	`$ ifort -qopenmp myprogram.f90 -o myprogram`	`$ gfortran -fopenmp myprogram.f90 -o myprogram`	`$ flang -fopenmp program.f90 -o program`
Fortran 95	`$ ifort -qopenmp myprogram.f90 -o myprogram`	`$ gfortran -fopenmp myprogram.f90 -o myprogram`	`$ flang -fopenmp program.f90 -o program`
C	`$ icc -qopenmp myprogram.c -o myprogram`	`$ gcc -fopenmp myprogram.c -o myprogram`	`$ clang -fopenmp program.c -o program`
C++	`$ icc -qopenmp myprogram.cpp -o myprogram`	`$ g++ -fopenmp myprogram.cpp -o myprogram`	`$ clang++ -fopenmp program.cpp -o program`

The Intel, GNU and AOCC compilers will not output anything for a successful compilation. Also, the Intel compiler does not recognize the suffix ".f95". You may use ".f90" to stand for any Fortran code regardless of version as it is a free-formatted form.

Here is some more documentation from other sources on OpenMP: