Phoebus: Performance Portable GRRMHD for Relativistic Astrophysics

TL;DR

PHOEBUS is an open-source, performance portable code for general relativistic radiation magnetohydrodynamics, enabling high-fidelity simulations of energetic astrophysical phenomena across diverse computational architectures.

Contribution

It introduces PHOEBUS, a novel GPU-first, scalable simulation code for GRRMHD with advanced radiation transport, built on the PARTHENON framework and supporting adaptive mesh refinement.

Findings

Successfully demonstrated weak scaling to over 500 GPUs.

Supports a large dynamic range in space and time.

Includes comprehensive physical and numerical modeling capabilities.

Abstract

We introduce the open source code PHOEBUS (phifty one ergs blows up a star) for astrophysical general relativistic radiation magnetohydrodynamic simulations. PHOEBUS is designed for, but not limited to, high energy astrophysical environments such as core-collapse supernovae, neutron star mergers, black-hole accretion disks, and similar phenomena. General relativistic magnetohydrodynamics are modeled in the Valencia formulation with conservative finite volume methods. Neutrino radiation transport is included with Monte Carlo and moment methods. PHOEBUS is built on the PARTHENON (Grete et al. 2022) performance portable adaptive mesh refinement framework, uses a GPU first development strategy, and is capable of modeling a large dynamic range in space and time. PHOEBUS utilizes KOKKOS for on-node parallelism and supports both CPU and GPU architectures. We describe the physical model employed in PHOEBUS, the numerical methods used, and demonstrate a suite of test problems to showcase its abilities. We demonstrate weak scaling to over 500 H100 GPUs.