Difference between revisions of "Building an MPI library"

Latest revision as of 13:00, 30 September 2026

There are a few freely available MPI libraries around; among the most widely spread are the OpenMPI https://www.open-mpi.org/ and MPICH https://www.mpich.org/ libraries

Checking if you have an Fortran enabled MPI library already installed and at hand

This can easily be done by checking if the MPI wrapper mpif90 is available, i.e. that

which mpif90

returns something meaningful

using a package manager

If you have sudo privileges and are on an Ubuntu or Linux Mint machine you should be able to install the OpenMPI library with

sudo apt install libopenmpi-dev openmpi-bin

Example of personal installation of the the OpenMPI library

To adapt to fit your own needs and system specificities, obviously. In the example below the installation is done in the $HOME/myopenmpi directory (for convenience this path is stored in the PATH_OPENMPI variable.

PATH_OPENMPI=$HOME/myopenmpi/
mkdir -p $PATH_OPENMPI
cd $PATH_OPENMPI
wget https://www.open-mpi.org/software/ompi/v1.10/downloads/openmpi-1.10.3.tar.gz
gunzip openmpi-1.10.3.tar.gz 
tar xvf openmpi-1.10.3.tar 
cd openmpi-1.10.3
./configure --prefix $PATH_OPENMPI
make all install

To check that the install went well check that

$PATH_OPENMPI/bin/mpif90 -V

returns something meaningful like

GNU Fortran (Ubuntu 9.4.0-1ubuntu1~20.04.1) 9.4.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Once you have a distribution correctly installed you will need to update your environment variables PATH and LD_LIBRARY_PATH to point to the relevant locations (the bin and lib subdirectories of the distribution). In practice this is typically done in your $HOME/.bash_profile or $HOME/.bashrc file, where for instance, if your installed the library in $HOME/myopenmpi you would add:

export PATH=$PATH:$HOME/myopenmpi/bin
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$HOME/myopenmpi/lib

A simple example to test your MPI installation

If you want to double check that all is well, you can for instance test with this ultra minimal program:

program simple_mpi
  use mpi

  implicit none
  
  integer :: myMPIRank, nbMPI
  integer :: code, level_mpi_provided

  ! Initialisation for MPI
  call MPI_INIT_THREAD(MPI_THREAD_FUNNELED,level_mpi_provided,code)
  call MPI_COMM_SIZE(MPI_COMM_WORLD,nbMPI,code)
  call MPI_COMM_RANK(MPI_COMM_WORLD,myMPIRank,code)  
  
  write(*,*) "Message from MPI process:",myMPIRank," of ", nbMPI

  ! finalize MPI region
  call MPI_FINALIZE(code)

end program simple_mpi

which you can compile, assuming the source code above is in file simple_mpi.f90, with:

mpif90 simple_mpi.f90 -l mpi -o simple_mpi

And then run on a few processors, e.g. 4, with:

mpirun -np 4 simple_mpi

which will return something like (order not guaranteed as all processes are simultaneously sending their message to the screen):

 Message from MPI process:           1  of            4
 Message from MPI process:           2  of            4
 Message from MPI process:           3  of            4
 Message from MPI process:           0  of            4

A few things worth knowing about

• mpif90 is just a wrapper around a given compiler which could be gfortran, ifort, pgfortran, etc. to know more about that run

mpif90 --version

• in some cases (e.g. with ifort) the Fortran wrapper is called mpifort or mpiifort (e.g. with ifort, sometimes), not mpif90
• It is vital to use the mpirun command from the same package than the mpif90 compilation wrapper used to compile the code. Otherwise one can get some really weird results...
• Likewise, if your MPI library is installed in a non-standard location you'll need to specify the path to it in your arch.fcm file (see The Target Architecture ("arch") Files) for the PCM,; e.g. if your MPI distribution is installed in /path/to/your/mpi/library:

%MPI_FFLAGS     -I/path/to/your/mpi/library/include
...
%MPI_LD         -L/path/to/your/mpi/library/lib -lmpi

24/09/2026