&ACE: The And-parallel Component of ACE (A Progress Report on ACE)

ACE is a computational model for full Prolog capable of concurrently exploiting both Or and Independent And-parallelism. In this paper we focus on the specific implementation of the And-parallel component of the system, describing its internal organization, some optimizations to the basic model, and finally presenting some performance figures. Keywords: Independent And-parallelism, Orparallelism, implementation issues. 1 Introduction The ACE (And-Or/Parallel Copying-based Execution) model [6] uses stack-copying [1] and recomputation [5] to efficiently support combined Or- and Independent And-parallel execution of logic programs. ACE represents an efficient combination of Or- and independent And-parallelism in the sense that penalties for supporting either form of parallelism are paid only when that form of parallelism is actually exploited. Thus, in the presence of only Or-parallelism, execution in ACE is exactly as in the MUSE [2] system---a stack-copying based purely Or-parallel s..