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Abstract:
Starting from a theoretical understanding of the usefulness logic of
a logic programming system with built-in tabling, and from a
collector that did not take the characteristics of a tabled abstract
machine into account we have build two heap garbage collectors (one
mark & slide, one mark & copy) for XSB on top of the CHAT
implementation model for the suspension/resumption of consumers.
Based on this experience we discuss implementation issues that are
general to heap garbage collection for the WAM and also issues that
are specific to an implementation with tabling: as such, this paper
documents our own implementation and can serve as guidance for
anyone attempting a similar feat. We report on the behaviour of the
garbage collectors on different kinds of programs. We also present
figures on the extent of internal fragmentation and the
effectiveness of early reset in Prolog systems with and without
tabling.