HPSF Conference 2025

The linear Boltzmann transport equation (BTE) is the governing equation for expressing the behaviour of neutral particles in a system such as a nuclear reactor. BTE can be solved for the flux of particles using deterministic methods whereby the equation is discretised in the phase space of is fundamental variables. This discrete equation is then usually solved using the source iteration. In this talk, we will present how the sweep algorithm which is based upon a wavefront pattern has been optimised in the context of SMP for CPU and also some preliminary results on GPU. The goal is to show how to adapt the sweep algorithm to be efficient on new supercomputer architectures.We will briefly introduce DONUT (Discrete Ordinates NeUtron Transport), a modern C++ miniapp for solving BTE based on the discrete ordinates and discontinuous Galerkin discretisations for Cartesian and honeycomb grids.