Lessons learned in porting Fortran/PVM code to the Cray T3D

We recently developed a portable, distributed solver for systems of equations, and implemented and optimized it on the Cray T3D supercomputer. To make the optimized code more accessible to the general scientist, we encapsulated the underlying details of distribution, constructing a prototype template to take advantage of Cray´s unique interface between its host computer and the T3D, while hiding the details of implementation from the applications programmer. We provide a first-hand account of the issues in porting Fortran/ PVM code to the Cray T3D. The Cray T3D offers low-level facilities for achieving substantial performance gains, but not without extra work from the programmer. Thus, it is often necessary to consider the tradeoffs between performance gains and coding effort