Introduction Two types of communicators exist within MPI Intra-communicators Inter -communicators This chapter will focus on intra- communicators that deal with communications among processes within individual communicators Inter-communicators on the other hand deal with communications t between intra-communicators Essentially intra-communicators are subsets of processes of MPI COMM WORLD The need for these new communicators is often driven by the need to deal subblock f a mat These communicators are often used in conjunction with a virtual topology more often than not a Cartesian topology -to facilitate implementation of parallel operations Furthermore, the use of communicators, and quite frequently together with virtual topology, generally enhances the readability and maintainability of a programIntroduction • Two types of communicators exist within MPI: – Intra-communicators – Inter-communicators. • This chapter will focus on intra-communicators that deal with communications among processes within individual communicators. • Inter-communicators, on the other hand, deal with communications between intra-communicators. • Essentially, intra-communicators are subsets of processes of MPI_COMM_WORLD. • The need for these new communicators is often driven by the need to deal with, for instance, rows, columns or subblocks of a matrix. • These communicators are often used in conjunction with a virtual topology - - more often than not a Cartesian topology -- to facilitate implementation of parallel operations. • Furthermore, the use of communicators, and quite frequently together with virtual topology, generally enhances the readability and maintainability of a program