CAT : the Copying Approach to

The SLG-WAM can be characterized as a sharing approach to implementing tabling: the execution environments of suspended computations are intersperced in the WAM stacks. Stacks are frozen using a set of freeze registers and the WAM trail mechanism is extended so that the suspended computations can be resumed. This technique has a reasonably small execution overhead, but is not easy to implement on top of an existing Prolog system. It is also quite diicult to understand. We propose a new technique for the implementation of tabling: the Copying Approach to Tabling. CAT does not interfere with normal Prolog execution and can be introduced in an existing Prolog system orthogonally. Also, CAT is easier to understand. We have implemented CAT starting from XSB by taking out SLG-WAM and adding CAT. We describe the additions needed for adopting CAT in a WAM implementation. We show a case in which CAT performs arbitrarily worse than SLG-WAM, but on the other hand we present empirical evidence that CAT is competitive and often faster than SLG-WAM. We also brieey discuss issues related to memory management and the impact of the scheduling.-is this true ?