Set Operations for Orthogonal Processor Groups

We consider a generalization of the SPMDpro gramming model for distributed memory machines based on orthogonal processor groups. In this model different partitions of the processors into disjoint processor groups exist and can be used simultaneously in a single parallel implementation. Set operations on orthogonal groups are used to express group-SPMDc omputations on different partitions of the processors. The set operations are implemented in MPI.