P2PDC is an environment for high performance peer to peer computing that allows direct communication between peers. This environment is based on P2PSAP, a self adaptive communication protocol. P2PDC is suited to the solution of large scale numerical simulation problems via distributed iterative methods. dPerf is a performance prediction environment for parallel and distributed applications, with primary interest in programs written in C, C++, Fortran for P2PDC. The dPerf performance prediction tool makes use of static and dynamic analyses combined with trace-based simulation. In this paper, we present a decentralized version of P2PDC and show how dPerf predicts performance for the P2PDC environment. We present new features of P2PDC aimed at making it more scalable and robust. Through experiments with P2PDC and dPerf, we show how to properly choose a peer to peer computing system which can match the computing power of a cluster.