Compiling Fortran

Some notes on compiling a Fortran program for OpenMP under AIX.

OpenMP library access

The easiest way to make the OpenMP library declarations available to a subroutine or function is to place the following line at the start of the subroutine:

use omp_lib

Alternatively, if the subroutines are all contained within a module then this line is needed just once in main body of the module.

Compile/build command

The following command builds an OpenMP executable called 'fubar' from two source files 'fu.f90' and 'bar.f90'

xlf90_r -q64 -qsmp=omp -qsuffix=f=f90 fu.f90 bar.f90 -o fubar

The option '-q64' is to enable 64-bit mode, required if your program exceeds the memory limit in 32-bit mode. The option '-qsuffix=f=f90' tells the compiler to accept files with the .f90 extension.