PeTar [github]

PeTar is a direct N-body code that integrates collisional stellar systems with more than one million particles without gravitational softening. PeTar uses a tree algorithm with a second-order leapfrog integrator for long-range forces but a fourth-order Hermite integrator with individual timesteps for short-range forces. In addition, the slow-down algorithmic regularization (SDAR) method is used for multiple systems such as hard binaries, triples, and hyperbolic encounters. PeTar also includes single/binary stellar evolution.

Wang et al. (2020) MNRAS [ADS]