SCYON Abstract

Received on: 01 07 2020

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

Authors:L. Wang 1,2, M. Iwasawa 2,3, K. Nitadori 2, J. Makino 2,4
Affiliations:(1) Department of Astronomy, School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan; (2) RIKEN Center for Computational Science, Chuo-ku, Kobe, Hyogo, Japan; (3) National Institute of Technology, Matsue College, Nishi-ikuma-cho, Matsue, Shimane, Japan; (4) Graduate School of Science, Kobe University, Nada-ku, Kobe, Hyogo, Japan
Accepted by: Monthly Notices of the Royal Astronomical Society

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 nuclear star clusters, becomes possible to be solved.

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