Author: Steven Edwards
Date: 06:25:08 09/18/03
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On September 18, 2003 at 04:57:02, Peter Fendrich wrote: >On September 18, 2003 at 04:18:35, Steven Edwards wrote: >>The programs Kaissa, Caps, and Paradise all had a causality facility. Such a >>feature is used for forward pruning in a manner suggestive of the human move >>selection process. The basic idea is: >> >>Given a subtree search of a position P with move M1 from P, the causality >>facility produces a causal data structure that contains the various constraints >>on the position and the move that allow the evaluation returned from the >>subsearch to be valid. Forward pruning is achieved when a move M2, a sibling of >>M1, can be applied to the causal data structure with the result that M2 doesn't >>violate any of the constraints and so doesn't need to be searched. >> >>It's not an easy problem, and some solutions may require more resources to >>calculate and probe the causal data than to do the unpruned search. >> >>Are there any current programs that have a causality facility? >During the search of M1 the program collects some values=constraints and builds >up a causal data strucuture. That structure is used during the search of M2-Mx >(siblings of M1). Right? Yes. >What kind of constraint values could that be? >How does that form a data structure? > >Do you have some example values... D] rnb1kbnr/ppp1pppp/8/3q4/8/2N5/PPPP1PPP/R1BQKBNR b KQkq - 1 3 A program is playing Black with the above root position as position "P". The first move on the list, M1, is a6. The search tries this and gets a poor score and a causal data structure. The program applies the next move M2 on the list, a5, to the data structure and sees that the constraints that produced the bad score for M1 also produce a simisar score for M2, so M2 is not searched. Some of the constraints in this case: 1. The wN/c3 remains there, unpinned, and able to capture bQ/d5 2. The bQ/d5 remains there and is undefended 3. Black has no known counterattacks or other resources within the depth of the subtree search.
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