Adapting AREPO-RT for Exascale Computing: GPU Acceleration and Efficient Communication

TL;DR

This paper enhances the AREPO-RT code for exascale supercomputers by implementing GPU acceleration and optimized communication strategies, significantly improving simulation speed and scalability for astrophysical radiative transfer modeling.

Contribution

It introduces GPU-based computation and a novel node-to-node communication method to optimize AREPO-RT for exascale architectures, enabling faster and more scalable astrophysical simulations.

Findings

GPU implementation yields ~15x speedup on benchmarks.

Communication optimizations improve performance on large and small-scale systems.

Overall efficiency triples in cosmological simulations of the Epoch of Reionization.

Abstract

Radiative transfer (RT) is a crucial ingredient for self-consistent modelling of numerous astrophysical phenomena across cosmic history. However, on-the-fly integration into radiation-hydrodynamics (RHD) simulations is computationally demanding, particularly due to the stringent time-stepping conditions and increased dimensionality inherent in multi-frequency collisionless Boltzmann physics. The emergence of exascale supercomputers, equipped with extensive CPU cores and GPU accelerators, offers new opportunities for enhancing RHD simulations. We present a novel optimization of AREPO-RT explicitly tailored for such high-performance computing environments. We implement a novel node-to-node communication strategy that utilizes shared memory to substitute intra-node communication with direct memory access. Furthermore, combining multiple inter-node messages into a single message substantially enhances network bandwidth utilization and performance for large-scale simulations on modern supercomputers. The single-message node-to-node approach also improves performance on smaller-scale machines with less optimized networks. Furthermore, by transitioning all RT-related calculations to GPUs, we achieve a significant computational speedup of around 15 for standard benchmarks compared to the original CPU implementation. As a case study, we perform cosmological RHD simulations of the Epoch of Reionization, employing a similar setup as the THESAN project. In this context, RT becomes sub-dominant such that even without modifying the core AREPO codebase, there is an overall threefold improvement in efficiency. The advancements presented here have broad implications, potentially transforming the complexity and scalability of future simulations for a wide variety of astrophysical studies.