IDEFIX: A versatile performance-portable Godunov code for astrophysical flows

Abstract

Context. The exascale super-computers becoming available rely on hybrid energy-efficient architectures that involve an accelerator such as a graphics processing unit (GPU). Leveraging the computational power of these machines often means a significant rewrite of the numerical tools each time a new architecture becomes available. Aims. We present IDEFIX, a new code for astrophysical flows that relies on the KOKKOS meta-programming library to guarantee performance portability on a wide variety of architectures while keeping the code as simple as possible to the user. Methods. IDEFIX is based on a Godunov finite-volume method that solves the nonrelativistic hydrodynamical (HD) and magnetohy-drodynamical (MHD) equations on various grid geometries. IDEFIX includes a large choice of solvers and several additional modules (constrained transport, orbital advection, nonideal MHD), allowing users to address complex astrophysical problems. Results. IDEFIX has been successfully tested on Intel and AMD CPUs (up to 131 072 CPU cores on Irene-Rome at TGCC) as well as NVidia and AMD GPUs (up to 1024 GPUs on Adastra at CINES). IDEFIX achieves more than 108 cell s−1 in MHD on a single NVidia V100 GPU and 3 × 1011 cell s−1 on 256 Adastra nodes (1024 GPUs) with 95% parallelization efficiency (compared to single node). For the same problem, IDEFIX is up to six times more energy efficient on GPUs compared to Intel Cascade Lake CPUs. Conclusions. IDEFIX is now a mature exascale-ready open-source code that can be used on a large variety of astrophysical and fluid dynamics applications.