PI Programming Environment for IBM SPl/SP2

In this paper we discuss an implementation of the M essage Passing I nterface standard (MPI) for the IBM Scalable Power PARALLEL 1 and 2 (SPl, SP2). Key to a reliable and efficient implementation of a message passing library on these machines is the careful design of a UNIX-Socket like layer in the u ser space with controlled access to the communication adapters and with adequate recovery and flow control. The performance of this i mplementation is at the s ame level as the IBMproprietary message passing library (MPL). We also show t hat in the IBM SPl and SP2 we achieve integrated tracing ability, where both system events, such as context switches and page fault etc., and MPI related activities are traced, with minimal overhead to the application program, thus presenting application programmers the trace of all the events that ultimately affect efficiency of a parallel program.