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Abstract : |
This paper describes ways of improving the performance of combined and-or parallel implementations. The model for and-or parallel execution of logic programs that we consider integrates the class of methods for exploiting or-parallelism which perform variable access and task-creation operations in constant-time (such as Binding Arrays method and Versions Vectors method) and the RAP method for independent and-parallelism. The major run-time overhead in such and-or parallel models can be traced back to the overhead incurred for or-parallelism during processor task switching. We present a number of techniques for reducing this overhead, by exploiting andparallelism and the semantics of Conditional Graph Expressions (CGEs). Essentially, we reduce the overhead by reducing the number of conditionally bound variables whose bindings need to be installed during task-switching. These techniques can be easily incorporated in a compiler, and can lead to substantial savings in execution time., |
