SWAN Tutorial

Wakis introduction and hands-on examples prepared to run on CERN's SWAN Service: https://swan.web.cern.ch/swan/:

Involving all our in-house python-packages of the impedance assessment workflow:

• Wakis for the 3D electromagnetic wakefield simulations,
• IDDEFIX for partially decayed wake extrapolation,
• BIHC for impedance-induced beam power loss, and
• neffint for impedance to wake function conversion for beam dynamics simulations.

SWAN confoguration

The suggested configuration for running Wakis on SWAN is to profit from the GPU resources available: Tesla T4(15 Gb) and A100 partition (40 Gb):

We suggest using the JupyterLab interface for easy access to the terminal for monitoring and better display of on-the-fly generated plots.

• ☑️ Try the new JupyterLab interface (experimental) - Recommended

To use Wakis on SWAN -or any user installed packages-, the following checkbox should be ticked:

• ☑️ Use Python packages installed on CERNBox - Needed

Installation

The installation on SWAN is done from the terminal (it can be opened from the launcher) and the pip install-ed packages are stored in your EOS:

• /eos/user/u/username/.local/bin Also, you can install wakis from GitHub to have the latest changes into your conda environment:

pip install wakis['notebook']
pip install bihc neffint iddefix # optional satellite packages

# To get the latest version from Github (non-deployed)
pip uninstall wakis -y
pip install git+https://github.com/ImpedanCEI/wakis.git

To generate 3D PyVista plots on SWAN, since it does not run an X-server, an extra step is needed to use OSMesa offscreen:

pip uninstall vtk -y
pip install --extra-index-url https://wheels.vtk.org vtk-osmesa

The 3D plots will be saved as an HTML scene that can be embedded with IFrame in the notebook. If the pyvista plots fail to make interactive plots and instead are stuck in static mode, it might be necessary to install or update trame:

pip install trame
pip install --upgrade trame-vdom trame-client trame-server trame-vuetify

To run mpi simulations in notebook 003, we need to update the ipyparallel package avialable in SWAN and install mpi4py:

pip install ipyparallel==9.0.1
pip install mpi4py

To work with Wakis on Swan in an elegant editor setup, navigate to the outer wakis folder (this folder was cloned previously from Git) with $\textbf{cd wakis}$ and go:

pip install -e .

Ops! Issues with importing the pip install-ed packages in the EOS have been experienced in this editor mode on Swan. Same applies to importing modules in the wakis package such as SolverFIT3D, even when changing the system path with sys.append(). However, these issues only occured when running notebooks located outside the Wakis root directory.