Effects of dynamic task distributions on the performance of a class of irregular computations

In this paper, a modified version of previously proposed quasi-barrier technique is developed. On distributed memory machines, relaxation with modified quasi-barriers can be used to perform basis computations that arise in symbolic polynomial manipulation. In this type of synchronous computation, the set of tasks is distributed across the processors. Each nonzero result of a task reduction dynamically generates a set of new tasks. The distribution of these newly generated tasks can have a significant impact on the overall execution time of the parallel computation. In this paper, four task distribution strategies, named modified block, modified sorted block, modified cyclic, and modified sorted cyclic are developed and their performances are comparatively evaluated. For the experiments performed on an 18-node IBM SP2, the modified cyclic distribution provides the best performance overall.