Author: Gian-Carlo Pascutto
Date: 02:34:35 01/25/01
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On January 24, 2001 at 23:39:12, Robert Hyatt wrote: >pushing a passed pawn had hardly any effect, but that might be a >result of the test suite rather than a useless extension. The default >value for this is also .75 > >recapture is the most interesting case. It actually appears that removing >this _completely_ gave the best score, which is surprising since >win at chess is a tactical suite. Lowering this extension obviously >speeds up the overall search. I currently use .75 here as well. > >The most interesting thing is the recapture extension. I have used it forever, >and took the idea from Cray Blitz since I used it there as well. I am not yet >sure why it actually hurts since it seems (to me) to be a logical idea. I am >going to test this more, just for my own interest. I have hesitated for a long time to add this extension for the following reason: you should use extensions to reduce the horizon effect, or on _really_ forced moves. Neither pushpp nor recapture do that when used like you do. Always extending checks, threats and onereply doesn't hurt much because they are forced anyway. For recaptures and pushpp that just isn't true. Recapturing happens often on different squares. Transpositions of moves fool the extension. Recapturing is a normal move. If you extend them you are blowing up your search with a _very_ small chance to find anything interesting. IMHO recapture extensions should only be done when close to the leaves, in order to prevent capture/recapture sequences from pushing a threat away. But when there is enough depth left, I see no reason to extend. Try your recapture extensions with varying trigger depth also. I think the results will be interesting at least. -- GCP
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