A new ray-tracing scheme for 3D diffuse radiation transfer on highly parallel architectures

TL;DR

This paper introduces an efficient, highly parallelized 3D diffuse radiation transfer scheme using ray-tracing, optimized for modern GPU and CPU architectures, with demonstrated scalability and validated through hydrogen photo-ionization simulations.

Contribution

A novel parallel ray-tracing scheme for 3D diffuse radiation transfer that scales well on multi-core and GPU architectures, enabling efficient large-scale simulations.

Findings

Scheme scales well with CPU cores and GPUs

Performance improves with increased computational resources

Validated through hydrogen photo-ionization simulations

Abstract

We present a new numerical scheme to solve the transfer of diffuse radiation on three-dimensional mesh grids which is efficient on processors with highly parallel architecture such as recently popular GPUs and CPUs with multi- and many-core architectures. The scheme is based on the ray-tracing method and the computational cost is proportional to $N_{\rm m}^{5/3}$ where $N_{\rm m}$ is the number of mesh grids, and is devised to compute the radiation transfer along each light-ray completely in parallel with appropriate grouping of the light-rays. We find that the performance of our scheme scales well with the number of adopted CPU cores and GPUs, and also that our scheme is nicely parallelized on a multi-node system by adopting the multiple wave front scheme, and the performance scales well with the amount of the computational resources. As numerical tests to validate our scheme and to give a physical criterion for the angular resolution of our ray-tracing scheme, we perform several numerical simulations of the photo-ionization of neutral hydrogen gas by ionizing radiation sources without the "on-the-spot" approximation, in which the transfer of diffuse radiation by radiative recombination is incorporated in a self-consistent manner.