Nested Parallel Call Optimization

We present a novel optimization called Last Parallel Call Optimization (LPCO) for parallel systems. The last parallel call optimization can be regarded as a parallel extension of last call optimization found in sequential systems. While the LPCO is fairly general, we use and-parallel logic programming systems to illustrate it and to report its performance on multiprocessor systems. The last parallel call optimization leads to improved time and space performance for a majority of and-parallel programs. We also present a generalization of the Last Parallel Call Optimization called Nested Parallel Call Optimization (NPCO). A major advantage of LPCO and NPCO is that parallel systems designed for exploiting control parallelism can automatically exploit data parallelism efficiently.