A Parallel Tree Code

We describe a new implementation of a parallel N-body tree code. The code is load-balanced using the method of orthogonal recursive bisection to subdivide the N-body system into independent rectangular volumes each of which is mapped to a processor on a parallel computer. On the Cray T3D, the load balance in the range of 70-90\% depending on the problem size and number of processors. The code can handle simulations with $>$ 10 million particles roughly a factor of 10 greater than allowed in vectorized tree codes.