TRUST: the HPC open-source CFD platform – from CPU to GPU

Since 1993, the CEA has developed <ns0:monospace>TRUST</ns0:monospace>, an open-source CFD software platform designed to address a wide range of thermohydraulic problems. Initially focused on nuclear applications, the platform has progressively evolved to support incompressible single-phase flows, low-Mach-number reactive flows, and fully compressible multi-phase flows. <ns0:monospace>TRUST</ns0:monospace> incorporates a variety of numerical schemes and supports multiple mesh types, making it suitable for both academic and industrial applications, as well as for deployment on standard computing systems and high-performance computing (HPC) clusters. Notably, it has enabled one of the largest Direct Numerical Simulations (DNS) to date for hydrogen risk assessment, involving over 2 billion cells and more than 50,000 <ns0:monospace>MPI</ns0:monospace> processors. Recently, the development team has begun integrating GPU-based computing technologies–such as <ns0:monospace>AmgX</ns0:monospace>, <ns0:monospace>rocALUTION</ns0:monospace>, <ns0:monospace>AMGCL</ns0:monospace> and <ns0:monospace>Kokkos</ns0:monospace>–to develop a hybrid CPU/GPU version of the code capable of delivering high performance across diverse architectures. This article presents an overview of the <ns0:monospace>TRUST</ns0:monospace> platform, reviews the largest simulation performed to date with the CPU version, outlines the ongoing GPU integration strategy, and highlights selected results.