The Message Passing Interface (MPI) is a standard for passing messages between multiple networked processes running a parallel program. As MPI is a standard, rather than a piece of software, there is not a single software package that you need to install. There are a few different 'flavours' of MPI, and the majority of HPC systems will have their own versions which are tuned for their specific systems. It is highly recommended that you use a system's built-in MPI libraries if they are available, but if not let's go through the process of installing an MPI library.
Requirements For this workshop you will need a multi-core machine which can run a unix-based terminal (i.e. Linux/WSL or Mac).
MPI can be easily installed with Homebrew. Check your machine has homebrew installed with
$ which brew
If this returns the location of the brew executable, then you can proceed with:
$ brew install open-mpi
An easy way to install MPI on Linux or WSL platforms is using the Spack package manager (this can also be done for MacOS but requires some additional steps).
In our case, we can install OpenMPI, which is a free and open source MPI implementation. OpenMPI can be installed in a number of different ways, but the recommended way is to use the Spack HPC package manager, which is in a class of its own in the way it handles different MPI implementations.
Spack is really simple to install, all you need to need to do is clone the Spack repository:
$ git clone --depth=100 --branch=releases/v0.21 https://github.com/spack/spack.git ~/spack
and source the included setup script:
$ source ~/spack/share/spack/setup-env.shEvery time you want to use Spack you will need to source this script, so it may be easier to add this to your shell login script, (i.e. ~/.bashrc, ~/.zshrc, etc.).
We need to let Spack find any compilers in our system, which we can do with:
$ spack compiler find
Note: This method requires you to have a working set of compilers for C and Fortran. If you don't have these on your system the simplest way to get them is to install the GNU compiler collection (GCC).
We can use Spack to install an MPI library, which will default to installing OpenMPI. If we run
$ spack spec mpi
we can see what Spack will install, and we can use
$ spack install mpi
to execute the installation. Once this is done, we can load the new mpi module with
$ spack load mpi
and check the installation with
$ which mpirun
This command tells us where the mpirun command has been installed, which is the primary way that we can launch an executable across multiple process with MPI. With the installation complete we are ready to run some programs with MPI.
Python is required for the first section of the course. If you do now have a working Python installation on your machine (you can check this with which python), you can follow the installation instructions from the CFRR Intro to Python course here.
Alternatively, Python can be installed with Spack, using a similar method to the MPI spack installation above. We need to run:
$ spack spec python
to see which version is available to be installed by default. We can then use
$ spack install python
to execute the installation. Once this is done, we can load the new Python module with
$ spack load python
and check the installation with
$ which python