PeTar: a high-performance N-body code for modeling massive collisional stellar systems

TL;DR

PeTar is a high-performance N-body simulation code that significantly accelerates modeling of massive collisional stellar systems, enabling million- and ten-million-body simulations with high accuracy and scalability.

Contribution

The paper introduces PeTar, a novel N-body code combining Barnes-Hut, Hermite integrator, and SDAR methods, achieving high performance and scalability for large stellar system simulations.

Findings

PeTar is 11 times faster than NBODY6++GPU for million-body simulations.

PeTar accurately reproduces the evolution of global structure and binary orbits.

The code scales well on supercomputers, enabling ten-million-body simulations.

Abstract

The numerical simulations of massive collisional stellar systems, such as globular clusters (GCs), are very time-consuming. Until now, only a few realistic million-body simulations of GCs with a small fraction of binaries (5%) have been performed by using the NBODY6++GPU code. Such models took half a year computational time on a GPU based super-computer. In this work, we develop a new N-body code, PeTar, by combining the methods of Barnes-Hut tree, Hermite integrator and slow-down algorithmic regularization (SDAR). The code can accurately handle an arbitrary fraction of multiple systems (e.g. binaries, triples) while keeping a high performance by using the hybrid parallelization methods with MPI, OpenMP, SIMD instructions and GPU. A few benchmarks indicate that PeTar and NBODY6++GPU have a very good agreement on the long-term evolution of the global structure, binary orbits and escapers. On a highly configured GPU desktop computer, the performance of a million-body simulation with all stars in binaries by using PeTar is 11 times faster than that of NBODY6++GPU. Moreover, on the Cray XC50 supercomputer, PeTar well scales when number of cores increase. The ten million-body problem, which covers the region of ultra compact dwarfs and nuclearstar clusters, becomes possible to be solved.