How to install Wi4MPI
======================

Learning objectives
-------------------

With these hands-on exercises, participants will learn:
 
- how to configure their environment in preparation for Wi4MPI installation
- how to install Wi4MPI using the Spack package manager
- how to configure Wi4MPI in their environment to efficiently use the library

Once participants complete these exercises, they will have a working Wi4MPI environment ready to use.

Installing Wi4MPI using Spack
------------------------------

Wi4MPI is available through Spack and the Spack package is updated with each new version.

Setup
^^^^^

To install Wi4MPI, one needs to first install a compiler supporting C, C++, and Fortran, given that these compilers are needed for MPI compilation. For example:

- Debian-like distro:

.. code-block:: bash

   (sudo) apt install gcc-11 g++-11 gfortran-11

- RHEL-like distro:

.. code-block:: bash

   (sudo) yum install gcc gcc-c++ gcc-gfortran

Spack installation
^^^^^^^^^^^^^^^^^^

Then, install and configure Spack using the compilers previously installed:

.. code-block:: bash

   git clone https://github.com/spack/spack.git
   source spack/share/spack/setup-env.sh
   spack compiler find

Once Spack is configured, you can install Wi4MPI and an alternative MPI implementation:

.. code-block:: bash

   spack install wi4mpi
   spack install mpich

Wi4MPI configuration
^^^^^^^^^^^^^^^^^^^^

Once Wi4MPI and the different MPI implementations are installed, Wi4MPI needs to be configured. To do so, the paths to the available MPI implementations need to be specified:

.. code-block:: bash

   spack load wi4mpi
   echo 'OPENMPI_DEFAULT_ROOT="</path/to/openmpi/root>"' >> $WI4MPI_ROOT/etc/wi4mpi.cfg
   echo 'MPICH_DEFAULT_ROOT="</path/to/mpich/root>"' >> $WI4MPI_ROOT/etc/wi4mpi.cfg

The above paths need to be updated with the actual paths on your system.