MPI-Rockstar: a Hybrid MPI and OpenMP Parallel Implementation of the Rockstar Halo finder

TL;DR

MPI-Rockstar is a hybrid MPI and OpenMP implementation of the Rockstar halo finder, enabling analysis of over a trillion particles on large supercomputers for cosmological research.

Contribution

It introduces a hybrid parallelization approach to Rockstar, supporting large-scale analysis and new output formats for advanced cosmological simulations.

Findings

Handles more than a trillion particles efficiently

Supports HDF5 output format and additional halo properties

Scales to over 100,000 parallel processes

Abstract

MPI-Rockstar is a massively parallel halo finder based on the Rockstar phase-space temporal halo finder code, which is one of the most extensively used halo finding codes. Compared to the original code, parallelized by a primitive socket communication library, we parallelized it in a hybrid way using MPI and OpenMP, which is suitable for analysis on the hybrid shared and distributed memory environments of modern supercomputers. This implementation can easily handle the analysis of more than a trillion particles on more than 100,000 parallel processes, enabling the production of a huge dataset for the next generation of cosmological surveys. As new functions to the original Rockstar code, MPI-Rockstar supports HDF5 as an output format and can output additional halo properties such as the inertia tensor.