Voir la source de Building an MPI library

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
<syntaxhighlight lang="bash">
which mpif90
</syntaxhighlight>
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
<syntaxhighlight lang="bash">
sudo apt install libopenmpi-dev openmpi-bin
</syntaxhighlight>

== Example of personal installation of the the OpenMPI library ==
To adapt to fit your onw needs and system specificities, obviously.
In the example below the installation is done in the '''$HOME/LMDZ''' directory (for convenience this path is stored in the '''PATH_OPENMPI''' variable. 
<syntaxhighlight lang="bash">
PATH_OPENMPI=$HOME/LMDZ/
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/openmpi-1.10.3
make all install
</syntaxhighlight>
To check that the install went well check that
<syntaxhighlight lang="bash">
$PATH_OPENMPI/openmpi-1.10.3/bin/mpif90 -V
</syntaxhighlight>
returns something meaningful like
<syntaxhighlight lang="bash">
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.
</syntaxhighlight>

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 '''$HOME/myopenmpi''' you would add:
<syntaxhighlight lang="bash">
export PATH=$PATH:$HOME/myopenmpi/bin
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$HOME/myopenmpi/lib
</syntaxhighlight>


== 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
<syntaxhighlight lang="bash">
mpif90 --version
</syntaxhighlight>
* in some cases (e.g. with ifort) the Fortran wrapper is called '''mpiifort''', 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... 

05/01/2022

[[Category:HowTo]]
[[Category:WhatIs]]