Getting started

Prerequisites

MPC has a few dependencies which must be installed prior to running the installation script. Most of them are available on most systems.

# Install dependencies on Centos
yum install -y gcc gcc-gfortran gcc-c++ patch make cmake automake libtool binutils bzip2 pkg-config curl python36 texinfo diffutils file
# Install dependencies on Debian / Ubuntu
apt install -y gcc g++ gfortran patch make cmake automake libtool binutils bzip2 pkg-config curl python3
# Install dependencies on Fedora
yum install -y gcc gcc-gfortran gcc-c++ patch make cmake bzip2 pkg-config findutils texinfo diffutils file
# Install dependencies on ArchLinux
pacman -Su gcc gcc-fortran patch make cmake bzip2 pkg-config python diffutils perl-podlators automake libtool binutils

Others dependencies are embedded with MPC source distribution and will downloaded/installed automatically.

Get MPC Source code

Two ways to retrieve MPC sources:

From a release (release page)

# Get the last tarball
curl -k https://github.com/cea-hpc/mpc/archive/refs/tags/MPC_4.3.1.tar.gz
# Extract the tarball
tar xf MPC_4.3.1.tar.gz

From the Git repository on Github

$ git clone https://github.com/cea-hpc/mpc.git

Building MPC

To ease the installation process of MPC and its dependencies, an unified installation script is provided , installmpc. You can run it from the extracted directory. Note that if MPC has been cloned from the Git repository, autoconf must be called beforehand to generate proper installation architecture (Makefile.in & configure scripts). From a release distribution, these files should be already provided.

# Considering this installation prefix (to change accordingly)
INSTALL_PREFIX=$PWD/INSTALL
# Run the install script
mkdir BUILD && cd BUILD
../installmpc --prefix=${INSTALL_PREFIX}

This will build MPC and its dependencies and may take a while, especially if the thread-based support is enabled (with --thread-based). To build MPC only in process mode (default), one may uses the --process-mode to the installmpc script. MPC supports Spack to reuse already installed packages to shorten the time to build. This behavior is the default and can be customized with --enable/disable-spack. Considering Spack is loaded to the current shell, MPC will try to find if deps (hwloc, openpa, libxml2, mpc-compiler-additions…) before building them. Additionally, MPC can install required dependencies through Spack to improve future builds by reusing them with --enable/disable-spack-build. This capability is disabled by default to avoid slowing down Spack installation with undesired packages.

Caution

Installation prefix should be set to avoid “default” installation path (usually under /usr/local) as MPC provides redefinition of few system headers (like pthread.h to intercept applications). It could lead to issues when MPC is not loaded. Additionally, MPC should be installed in a non-root environment.

Using MPC

To load MPC in the current environment, a sourcing script is made available in the install prefix:

$ source ${INSTALL_PREFIX}/mpcvars.sh

Compiling applications

MPC provides multiple entry-points to build applications. Beyond the classical mpicc, mpicxx/mpic++ and mpif* scripts, MPC comes with its own sets of compiler scripts named after the language it targets: mpc_cc, mpc_cxx & mpc_f77 (common wrapper for any Fortran standard).

The main difference between these two sets of scripts can be identified when MPC is built in thread-based mode: mpi* scripts does not privatize applications by default with a thread-based installation, while mpc_* script will privatize by default. This is intended to transparently capture applications assuming mpi* scripts without silently attempting to privatize them. This way, applications built with “conventional” MPI wrappers can be supported. To conveniently enable privatization without propagating any compilation flag, it can be done through environment variables:

# Considering a "thread-based" installation
# Compilation with automatic privatization
mpc_cc main.c
# Compilation WITHOUT automatic privatization
mpicc main.c

# All the lines below are equivalent and enables automatic privatization
mpc_cc main.c mpc_cc -fmpc-privatize main.c
mpicc -fmpc-privatize main.c MPI_PRIV=1 mpicc main.c

Without providing any further option, MPC is installed with no thread-based MPI support, implying multiple MPI processes can not live within the same UNIX process. The privatization is implied if the --thread-based installation parameter was passed.

Note

MPC can be installed in thread-based configuration by using the --thread-based option to the installmpc script.

Running applications

MPC provides two entry points for launching applications. The regular mpirun and mpcrun. The latter gives more control on many aspects of running in complex environments. Most of runtime options are available as configuration environment variables, most scenarios have a equivalent in both scripts.

Note

While mpcrun is a Bash-based Shell script, mpirun is a Python script.

The strength of MPC in thread-based mode is to allow MPI processes to run inside regular UNIX processes. For this purpose, an extra set of options is added when defining such parameter is required. Both must be set when running an application. With mpirun, one can be extrapolated from the other:

# Two MPI processes, two UNIX processes
mpirun -np 2 ./a.out

# Two MPI processes, one single UNIX processes
# Considering ./a.out as a privatized application
mpirun -np 2 -p 1 ./a.out
mpirun -n 2  -p 1 ./a.out
mpcrun -n=2  -p=1 ./a.out

# Running on multiple nodes, one UNIX process per node of two MPI processes each
mpirun -N 2 -n 4 -p 2 ./a.out

# Restrict number of cores bound to EACH process
# Note:
# * PpN = '-p' / '-N' = number of processes per node
# the number of cores required per node (PpN * '-c') must not exceed the
# maximum number of cores on a single node
mpirun -N 2 -n 4 -p 2 -c 4 ./a.out

Note

MPC is configured to run with the launcher detected during the installation phase. To list available launchers (Hydra, SLURM…): mpcrun --launch_list, to then be used with -l option.