An Extension to MPI for Distributed Computing on MPPs

We present a tool that allows to run an MPI application on several MPPs without having to change the application code. PACX (PArallel Computer eXtension) provides to the user a distributed MPI environment with most of the important functionality of standard MPI. It is therefore well suited for usage in metacomputing. We are going to show how two MPPs are conngured by PACX into a single virtual machine. The underlying communication management that makes use of highly optimized MPI for internal communication and uses standard protocols for external communication is presented. The performance of PACX for several basic message-passing calls is described. This covers latency, bandwidth, synchronization and global communication.