HPC systems

The information provided in this page is for users who intend to work on High-Performance Computing (HPC) systems. These installation instructions are system-specific. X-PSI has already been used on different systems, for some of which we provide the instructions below. This information may also be translated to other systems by users looking for guidance.

Snellius (SURF)

Snellius is the Dutch National Supercomputer.


All of the following must be performed on a login node, in your $HOME file system.

Start by cleaning your home file system of existing versions of dependencies and move anything else to some archive in $HOME. Clean .bashrc and .bash_profile of anything related to this software. Clean .bashrc and .bash_profile of environment variables such as: LD_LIBRARY_PATH, LD_PRELOAD, RUN_PATH, PATH, and PYTHONPATH. Then logout and log back in order to get a clean environment.

To be additionally safe, run:

module purge

Load environment module and modify clean environment with foss toolchain information and the needed modules:

module load 2022
module load foss/2022a
module load SciPy-bundle/2022.05-foss-2022a
module load wrapt/1.15.0-foss-2022a
module load matplotlib/3.5.2-foss-2022a
module load CMake/3.23.1-GCCcore-11.3.0

Prepare a new Python virtual environment for X-PSI (named for example “xpsi_py3”) in case the possibility of having several co-existing X-PSI and/or PyMultiNest versions is wished (otherwise proceed to MultiNest installation):

mkdir venvs
python -m venv ./venvs/xpsi_py3

To access all the loaded site packages when activating the virtual environment, one needs to modify the file ./venvs/xpsi_py3/pyvenv.cfg (using e.g. vim or emacs text editor) to change “false” into “true”:

Include system site packages = true

Now the environment can be activated with

source ./venvs/xpsi_py3/bin/activate

To prepare MultiNest from $HOME:

git clone https://github.com/farhanferoz/MultiNest.git ~/multinest
cd ~/multinest/MultiNest_v3.12_CMake/multinest
mkdir build; cd build
cmake -DCMAKE_{C,CXX}_FLAGS="-O3 -march=znver2 -funroll-loops" -DCMAKE_Fortran_FLAGS="-O3 -march=znver2 -funroll-loops" ..; make
ls ../lib/

Use the last command to check for the presence of shared objects.

We also need to set the environment variable for library path to point at MultiNest:

export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$HOME/multinest/MultiNest_v3.12_CMake/multinest/lib/

Now you need the Python interface to MultiNest, starting from $HOME:

git clone https://github.com/JohannesBuchner/PyMultiNest.git ~/pymultinest
cd ~/pymultinest
python setup.py install


If not using a Python virtual environment, you should add --user flag when installing PyMultiNest.

To test the installation of MultiNest and PyMultiNest on the login node:

mpiexec -n 2 python pymultinest_demo.py

Do you obtain parameter values and evidences?


Without knowing exactly the reason, we currently get typically this message Open MPI failed an OFI Libfabric library call (fi_domain).  This is highly unusual; your job may behave unpredictably (and/or abort) after this. when doing this test. However, the test works otherwise as expected, and this message seem not to appear when submitting jobs in the cluster instead of using the login node.


We assumed above that nested sampling with MultiNest is desired. If ensemble-MCMC with emcee is desired, you need to install the Python packages emcee and schwimmbad. We assume the user can infer how to do this using the information above and on the Installation page.

For GSL we can use the default 2.5 version already provided in Snellius. Thus, to prepare X-PSI from $HOME, we only need:

git clone https://github.com/xpsi-group/xpsi.git
cd ~/xpsi
LDSHARED="gcc -shared" CC=gcc python setup.py install


If not using a Python virtual environment, you should add --user flag when installing X-PSI.

If you ever need to reinstall, first clean to recompile C files:

rm -r build dist *egg* xpsi/*/*.c xpsi/include/rayXpanda/*.o


We typically do not use the PostProcessing module, but instead rsync output files to a local system to perform plotting. This circumvents any potential backend problems and permits straightforward use of IPython for interactive plotting. However, if one wishes to use it on an HPC, it would require the installation of GetDist and Nestcheck. See Installation page for relevant details.

Batch usage

For an example job script, refer to Example job.

Lisa (SURF)

Lisa follows mostly the installation instructions as that of Snellius. Small differences in the installation procedure are still to be studied.

Helios (API)

Helios is a cluster of the Anton Pannekoek Institute for Astronomy.


Let’s start by loading the necessary modules and creating a conda environment. At the moment, the installation is known to be working only for the specific python 3.10.6 version, and when conda installing the required python packages separately, as followed:

module load anaconda3/2021-05
module load openmpi/3.1.6
git clone https://github.com/xpsi-group/xpsi.git
cd xpsi
conda create -n xpsi_py3 python=3.10.6
conda activate xpsi_py3
conda install -c conda-forge mpi4py
conda install cython~=0.29
conda install scipy
conda install matplotlib
conda install wrapt

Let’s then test if mpi4py works:

cd; wget https://github.com/mpi4py/mpi4py/releases/download/3.1.5/mpi4py-3.1.5.tar.gz
tar zxvf mpi4py-3.1.5.tar.gz
cd mpi4py-3.1.5
mpiexec -n 4 python demo/helloworld.py

Let’s then install MultiNest and PyMultiNest:

cd; git clone https://github.com/farhanferoz/MultiNest.git multinest
cd multinest/MultiNest_v3.12_CMake/multinest
mkdir build
cd build
CC=gcc FC=/zfs/helios/filer0/sw-astro/api/openmpi/3.1.6/bin/mpif90 CXX=g++ cmake -DCMAKE_{C,CXX}_FLAGS="-O3 -march=native -funroll-loops" -DCMAKE_Fortran_FLAGS="-O3 -march=native -funroll-loops" ..
cd; git clone https://github.com/JohannesBuchner/PyMultiNest.git pymultinest
cd pymultinest
python setup.py install

We can then check, if the PyMultiNest installation works:

export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$HOME/multinest/MultiNest_v3.12_CMake/multinest/lib/
mpiexec -n 2 python pymultinest_demo.py

Let’s then install GSL:

cd; wget -v http://mirror.koddos.net/gnu/gsl/gsl-latest.tar.gz
tar -xzvf gsl-latest.tar.gz
cd gsl-{latest}
./configure CC=gcc --prefix=$HOME/gsl
make check
make install
make installcheck
make clean
export PATH=$HOME/gsl/bin:$PATH

where gsl-{latest} should be replaced with the latest version number. Let’s then finally install X-PSI and test that it works:

cd; cd xpsi;
CC=gcc python setup.py install
cd examples/examples_fast/Modules/
python main.py

Batch usage

For example job scripts, see the Helios example in Example job.


CALMIP is the supercomputer of Université Fédérale de Toulouse


In your $HOME file system, from the login node, start by loading the necessary modules:

module purge
module load conda
module load cmake
module load intel/18.2.199
module load intelmpi/18.2
module load gsl/2.5-icc

Then, create the conda environnnement and Install python packages with conda (or pip):

conda create -n xpsi --clone base
conda activate xpsi
conda install numpy scipy matplotlib wrapt
conda install cython~=0.29
conda install h5py
conda install -c conda-forge fgivenx
pip install schwimmbad --user

Point to the Intel compilers

export FC=ifort
export CC=icc
export CXX=icpc

Install mpi4py in your $HOME (e.g. in ~/Softwares):

mkdir Softwares
cd Softwares
wget https://github.com/mpi4py/mpi4py/releases/download/3.1.5/mpi4py-3.1.5.tar.gz
tar zxvf mpi4py-3.1.5.tar.gz
cd mpi4py-3.1.5
python setup.py build
python setup.py install
# Test on login node:
mpiexec -n 4 python demo/helloworld.py

Download and Install the MultiNest package in your $HOME (e.g. in ~/Softwares:

cd ~/Softwares
git clone https://github.com/farhanferoz/MultiNest.git  ./MultiNest
cd MultiNest/MultiNest_v3.12_CMake/multinest/
mkdir build
cd build
cmake -DCMAKE_INSTALL_PREFIX=~/Softwares/MultiNest \
            -DCMAKE_{C,CXX}_FLAGS="-O3 -xCORE-AVX512 -mkl" \
            -DCMAKE_Fortran_FLAGS="-O3 -xCORE-AVX512 -mkl" \
            -DCMAKE_C_COMPILER=mpiicc    \
            -DCMAKE_CXX_COMPILER=mpiicpc \
            -DCMAKE_Fortran_COMPILER=mpiifort  ..

## Check that libraries have been compiled and are present
ls ../lib

Install pymultinest in your $HOME (e.g. in ~/Softwares:

cd ~/Softwares
git clone https://github.com/JohannesBuchner/PyMultiNest.git ./pymultinest
cd pymultinest
python setup.py install

# Add MultiNest to Library Path to test PyMultiNest (action to do for every job to run)
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$HOME/Softwares/MultiNest/MultiNest_v3.12_CMake/multinest/lib

# Test pymultinest
mpiexec -n 2 python pymultinest_demo.py

Clone and Install X-PSI in ~/Softwares/

cd ~/Softwares
git clone https://github.com/xpsi-group/xpsi.git
cd xpsi/
LDSHARED="icc -shared" CC=icc python setup.py install

# Test installation
cd ~/
python -c "import xpsi"

## Ignore the warnings about GetDist, NestCheck, CornerPlotter
##  which are only for PostProcessing (not usually performed on HPC systems).

Set up your library paths:

export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$HOME/Softwares/MultiNest/MultiNest_v3.12_CMake/multinest/lib
export LD_PRELOAD=$MKLROOT/lib/intel64/libmkl_core.so:$MKLROOT/lib/intel64/libmkl_sequential.so

Note that the module commands, and the library path commands above will have to be added in your SBATCH script (see Example job) to execute a run.