Compiling OpenMP Programs

All compilers installed on Brown 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

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
Fortran 77	`$ ifort -openmp myprogram.f -o myprogram`	`$ gfortran -fopenmp myprogram.f -o myprogram`
Fortran 90	`$ ifort -openmp myprogram.f90 -o myprogram`	`$ gfortran -fopenmp myprogram.f90 -o myprogram`
Fortran 95	`$ ifort -openmp myprogram.f90 -o myprogram`	`$ gfortran -fopenmp myprogram.f95 -o myprogram`
C	`$ icc -openmp myprogram.c -o myprogram`	`$ gcc -fopenmp myprogram.c -o myprogram`
C++	`$ icc -openmp myprogram.cpp -o myprogram`	`$ g++ -fopenmp myprogram.cpp -o myprogram`

The Intel and GNU compilers will not output anything for a successful compilation. Also, the Intel compiler does not recognize the suffix ".f95".

Here is some more documentation from other sources on OpenMP: