A High Performance Prolog Processor With Multiple Function Units

We describe the Parallel Unification Machine (PLUM), a Prolog processor that exploits fine grain parallelism using multiple function units executing in parallel. In most cases the execution of bookkeeping instructions is almost completely overlapped by unification, and the performance of the processor is limited only by the available unification parallelism. We present measurements from a register transfer level simulator of PLUM. These results show that PLUM with 3 Unification Units achieves an average speedup of approximately 3.4 over the Berkeley VLSI- PLM, which is usually regarded as the current highest performance special purpose, pipelined Prolog processor. Measurements that show the effects of multiple Unification Units and memory access time on performance are also presented.