Hierarchical decomposition: A parallel implementation of the Barnes-Hut tree algorithm

Given the coordinates of N points in D dimensions, the Barnes-Hut tree algorithm produces an ordered list so that successive pairs in the sequence are nearest neighbors, sets of four form a cluster, sets of eight form a bigger cluster, and so on. We describe a parallel implementation of this algorithm on the IBM SP2 using Fortran 77 and MPI message-passing calls, and study its performance.