An abstract machine to implement or-and parallel PROLOG efficiently

PEPSys (Parallel ECRC PROLOG System) is a research project started in 1984 in the Computer Architecture Group of the European Computer-Industry Research Centre (ECRC). Its general goals are to study and evaluate new and practicable solutions to the problems of parallel logic programming. The PEPSys Abstract Machine described in this paper was designed to allow an efficient implementation of the PEPSys computational model. Based on the WAM, it incorporates a number of novel features to support the management of the logical variable and the control of the search space of the PEPSys computational model. Both a parallel implementation on a multiprocessor and a simulation system of scalable multiprocessor architectures implement the PEPSys Abstract Machine and yield effective speedups in parallel computations.