Get started with GBS

Table of Contents

• Obtaining GBS
• Compiling GBS
  • Required libraries
    • Note for Marconi users
  • Setting up CMake
• Running GBS

This page explains how to obtain and compile the GBS code

Obtaining GBS

The GBS code is version controlled using git and the central repository is hosted on the c4science.ch platform. To access it, you must create a c4science account and then ask for access to the source code (precising your c4science username) by email to paolo.nosp@m..ric.nosp@m.ci@ep.nosp@m.fl.c.nosp@m.h.

Once you have been granted access, you can clone the GBS repository using:

git clone https://c4science.ch/source/gbs.git

or

git clone ssh://git@c4science.ch/source/gbs.git

Depending on the chosen protocol (https or ssh) you will need to setup either a VCS password or a public ssh key.

Compiling GBS

Required libraries

The GBS code relies on many different libraries. The following are mandatory:

• BLAS implementation
• MPI implementation
• HDF5

For the solvers, you can choose one of the following:

• PETSc (preferred) or MUMPS or scaLAPACK

One other in-house library, futils, is packaged with GBS and compiled automatically.

Note for Marconi users

On Marconi, there are a few extra steps to perform before being able to compile GBS using CMake. First of all, here are the modules you need to load:

module load  intel  intelmpi  mkl  szip  zlib  cmake  hdf5  petsc/3.13.3--intelmpi--2018--binary  parmetis

Note that it is important to load the PETSc module without the _complex in the name. Otherwise, it will also provide an FFTW interface, which will cause problems.

Then, add the following in your .bashrc file on Marconi:

export PKG_CONFIG_PATH=${PETSC_LIB}/pkgconfig:$PKG_CONFIGPATH
export METIS_HOME=${PETSC_HOME}; export MUMPS_HOME=${PETSC_HOME}

The first line is used to tell CMake where to find PETSc (it is a missing configuration on their module) and the second line tells CMake to use Metis and MUMPS provided by the PETSc module. For some reason, it does not work with the standalone modules provided on Marconi.

This concludes the configuration specific to Marconi. You can now proceed as explained at the beginning of Setting up CMake.

Setting up CMake

The configuration and compilation of the code is done using CMake and Make. In the GBS root directory, the following commands are used to create a directory and setting up CMake:

mkdir build
cd build
cmake ..

CMake will automatically search for the required libraries and set up a makefile. Once the configuration is done, you can either compile the code as is using

make

or customize the compilation options using

ccmake ..

This will open a GUI with a summary of the different options available for GBS

Running GBS