Scalable parallel formulations of the Barnes-Hut method for n-body simulations

We present two new parallel formulations of the Barnes-Hut method. These parallel formulations are especially suited for simulations with irregular particle densities. We first present a parallel formulation that uses a static partitioning of the domain and assignment of subdomains to processors. We demonstrate that this scheme delivers acceptable load balance, and coupled with two collective communication operations, it yields good performance. We present a second parallel formulation which combines static decomposition of the domain with an assignment of subdomains to processors based on Morton ordering. This alleviates the load imbalance inherent in the first scheme. The second parallel formulation is inspired by two currently best known parallel algorithms for the Barnes-Hut method. We present an experimental evaluation of these schemes on a 256 processor nCUBE2 parallel computer for an astrophysical simulation