Communication Set Generation for a Special Case of Irregular Parallel Applications

Abstract

Irregular computing significantly influences the performance of large scale parallel applications.How to generate local memory access sequence and communication set efficiently for irregular array reference is an important issue in compiling a data-parallel language into a single program multiple data(SPMD) code for distributed-memory machines.By far,many researches have focused on the problem of communication set generation under regular array references in parallel loops.However,little researches give attentions to generating communication set for irregular array accesses in loop nests.In general case of irregular accesses,Inspector/Executor model is adopted to scan over array elements at Inspector phase of run time such that communication set can be constructed.This paper proposes an approach to derive an algebraic solution of communication set enumeration at compile time for the situation of irregular array references in nested loops.And this paper introduces integer lattice into alignment and cyclic(k)-distribution for global-to-local and local-to-global index translations.Then it also presents the algorithm for the corresponding SPMD code generation.When the parameters of alignments and cyclic(k) and array references are known,the SPMD code can then be completely derived at compile time such that no inspector-like run-time code will be needed to construct enumeration of the communication set.