Development of the Persistent Actor Framework (PAF) version of the European Transport Simulator (ETS)

Paper in proceeding, 2025

The first version of the ETS was developed within the EFDA Work Package on Integrated Tokamak Modelling [ETS-2008, ETS-2010a, ETS2010b]. That version was essentially a Fortran workflow using Consistent Physical Objects (CPOs)[CPO-2010] to couple a number of codes providing the standard building blocks of a core plasma simulation (equilibrium codes, the calculation of sources and transport coefficients, and the transport solver). To allow for the inclusion of components in other languages, KEPLER [KEPLER-2006] was used as a coupling environment [ETS-2012, ETS-2013a, ETS-2013b, ETS-2014, ETS-2018, ETS-2019, ETS2021a], and after some years of using CPOs, these were replaced by Interface Data Structures (IDSs) [IMAS-2015] [ETS-2020, ETS-2021b, ETS-2022, ETS-2024]. This has been in use for a number of years, but the decision has been made to look at other coupling frameworks. This contribution describes the development of the ETS-PAF, which uses the MUSCLE3 framework [MUSCLE3-2020] to couple the various physics modules (mostly in fortran, C or C++), together with python modules to implement some of the workflow logic. The workflow takes the form of a number of separate programs (currently about 60) that communicate IDSs to other programs via one-way communication channels (currently about 150) sending/receiving IDSs.