# TSVV12 IMAS

## Fast particle and 3D equilibrium code interfaces
The goal of this task is to interface fast particle and 3D equilibrium codes. In particular, ASCOT5 and BEAMS3D should leverage IMAS-compatible data structures. Support is needed to properly define said interfaces, and help with integration of fast particle codes into the IMAS framework. In addition to this, interfacing of VMEC/GVEC into IMAS so that 3D equilibria may also be included in the framework is desirable.
BEAMS3D has an existing ability to interface to axisymmetric equilibria (EQDSK g-files). The predeceding major version of ASCOT, ASCOT4 is already part of IMAS, though in 2D. Thus, a significant intellectual effort has already been invested. However, the 3D quantities are stored in fundamentally more complex data structures for which the 2D cases are only a starting point.
This should have high to medium priority as it is a key SMART deliverable in the 2021/2022 timeframe. It is expected that 6+6=12 PM of ACH support would be required. It is also noted that this is the first time a 3D stellarator code is integrated into the IMAS framework, further motivating the high priority.

## GPU ASCOT5
The goal of this task is to complete implementation of GPU acceleration of ASCOT5 for stellarator configurations. ASCOT5 is written in C with OpenMP+MPI parallelism.
OpenMP supports also offloading to i.a. GPUs, but this is a new and developing feature with limited documentation and tool support.
The implementation and optimization of GPU offloading support of ASCOT5 has commenced in 2020 as HLST work by EPFL (same people as now moving to ACH-EPFL). Single modalities of the code have been modified to run with with GPU offloading. The key features for stellarators, 3D magnetic field and 3D wall, need adaptation work and optimization of performance.

ACH support is needed in the implementation, profiling, optimization and compiler maintenance needed for the OpenMP-offloading architecture employed in ASCOT5. This should have high priority as it is a key SMART deliverable in the 2022 timeframe. It is expected that 12 PM of ACH support would be required.