Build OpenMPI for Fortran

While GNU Gfortran and Intel oneAPI have easy-to-use OpenMPI support pre-built for many platforms, it can be desirable to compile OpenMPI to get the latest version or to support other compilers. Compiling OpenMPI is quite easy and takes only several minutes to compile.

Download latest OpenMPI source Configure OpenMPI with Fortran compiler:

./configure --prefix=~/.local/openmpi CC=gcc CXX=g++ FC=gfortran

Don’t just use ~/.local as that spills OpenMPI files into common directories, making it hard to use multiple OpenMPI versions or multiple compilers.

Build and install OpenMPI:

make -j

make install   # no sudo

Add to ~/.profile:

export LD_LIBRARY_PATH=$HOME/.local/openmpi/lib:$LD_LIBRARY_PATH

The FindMPI CMake module allows switching between multiple OpenMPI versions installed with MPI_ROOT variable:

cmake -DMPI_ROOT=~/.local/openmpi/lib ..

As in general for CMake packages, the MPI imported target is highly recommended over the legacy discrete variables, as in this minimal CMakeLists.txt:

find_package(MPI REQUIRED COMPONENTS Fortran)

add_executable(mpivers mpivers.f90)
target_link_libraries(mpivers MPI::MPI_Fortran)

Troubleshooting:

If it doesn’t work with CMake, try ~/.local/openmpi/bin/mpif90 myprog.f90. If that works, try something like:

FC=gfortran CC=gcc cmake -DMPI_Fortran_COMPILER=~/.local/openmpi/bin/mpif90 ..

Examples: modern Fortran 2008 OpenMPI examples


Related: MPI for MinGW GCC / GFortran on Windows