SPMD image processing on Beowulf clusters: directives and libraries

Most image processing algorithms can be parallelized by splitting parallel loops and by using very few communication patterns. Code parallelization using MPI still involves much programming overhead. In order to reduce these overheads, we first developed a small SPMD library (SPMDlib) on top of MPI. The programmer can use the library routines themselves, because they are easy to learn and to apply, even without knowing MPI. However, in order to increase user friendliness, we also develop a small set of parallelization and communication directives/pragmas (SPMDdir), together with a parser that converts these into library calls. SPMDdir is used to develop a new version of SPMDlib. This new version contains much less but generic routines that can be optimized for different network topologies. Extensions for Fortran 90/95 and C are discussed, as well as communication optimizations.