Abstract of A5TOGPU Project

The ASCOT5 code is the latest core tool in the well-established ASCOT suite of fast ion modelling codes. It is already used to model NBI ions, fusion alpha particles and tritons in i.a. ITER, JET, ASDEX Upgrade, W7-X, MAST and MAST-U. It is also gaining ground as a go-to fast ion modelling tool in US and commercial fusion research organizations.

ASCOT5 is originally written for the Intel Xeon Phi MIC platform using OpenMP offloading pragmas in C. The code runs nearly fully SIMD vectorised. Multi-node parallelisation is done with MPI.

Intel has discontinued the Xeon Phi line of products, so the code needs to be adapted to the GPGPU environment. The recent OpenMP 4.5 facilitates GPGPU offloading, so the work in transitioning from Xeon Phi to GPGPU should be manageable. Indeed, first trial runs were successful. However, the work requires advanced steps, such as compiling the needed compilers and in-depth understanding of GPGPU programming. Thus, expert support from HLST should allow the code to quickly reach maximum performance on GPGPUs.