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

• Main Authors: Lesur, G. R. J, Baghdadi, S, Wafflard-Fernandez, G, Mauxion, J, Robert, C. M. T, Bossche, M. Van den
• Format: Journal Article
• Language: English
• Published: 26-04-2023
• Subjects: Physics - High Energy Astrophysical Phenomena; Physics - Instrumentation and Methods for Astrophysics; Physics - Solar and Stellar Astrophysics
• DOI: 10.48550/arxiv.2304.13746

A&A 677, A9 (2023) Exascale super-computers now becoming available rely on hybrid
energy-efficient architectures that involve an accelerator such as Graphics
Processing Units (GPU). Leveraging the computational power of these machines
often means a significant rewrite of the numerical tools each time a new
architecture becomes available. To address these issues, 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 for the user. Idefix is based on a
Godunov finite-volume method that solves the non-relativistic HD and MHD
equations on various grid geometries. Idefix includes a wide choice of solvers
and several additional modules (constrained transport, orbital advection,
non-ideal MHD) allowing users to address complex astrophysical problems. 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 1e8 cell/s in MHD on a single NVidia V100
GPU and 3e11 cell/s on 256 Adastra nodes (1024 GPUs) with 95% parallelization
efficiency (compared to a single node). For the same problem, Idefix is up to 6
times more energy efficient on GPUs compared to Intel Cascade Lake CPUs. Idefix
is now a mature exascale-ready open-source code that can be used on a large
variety of astrophysical and fluid dynamics applications.