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Multi-Threaded Tabled Logic Programing

Tabling has proven to be an important addition to logic programming, and has provided a declarative way to solve problems in verification, natural language analysis, agent-based reasoning, and semantic web applications, among others. At the same time, newer multi-core computer architectures have sparked renewed research into features for multi-threading and parallelism for a number of languages including Prolog. This talk summarizes recent research, done jointly with Rui Marques and Jose Cunha of Universidade Nove de Lisboa, into multi-threaded tabled logic programming in the XSB system. Tables in XSB can be either private to a thread or shared among threads. XSB supports numerous functions for thread-private tables, including tabled negation over the well-founded semantics, call and answer subsumption, and tabled constraints. Most of these features can also be used by thread-shared tables. However, when sharing tables among threads, numerous concurrency issues arise, giving rise to new algorithms for concurrent and parallel tabling.