Author: Robert Hyatt
Date: 05:29:56 05/30/99
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On May 29, 1999 at 23:31:38, Jeremiah Penery wrote: >On May 29, 1999 at 17:42:46, Robert Hyatt wrote: > >>On May 29, 1999 at 17:13:59, James T. Walker wrote: >> >>>Programmers, >>>How do you exit the tablebases when the next tablebase is missing? For example: >>> In KQPKQ when the pawn reaches the 8th rank and upon promotion is captured by >>>the opposing Queen. This is not in the KQPKQ tablebase so how do you force the >>>program to make the pawn move which actually drops out of the "safety" of the >>>tablebase? Since the KQQKQ tablebase was missing as was the KQK tablebase. >>>The reason I ask is I saw one program reach "Mate in 13" but played about 6 >>>moves around the mate in 13 area before pushing the pawn and making progress. >>>Jim Walker >> >> >>This is a problem. And this is why I _always_ tell anyone using my code >>that if you get a k?pk? database, you _must_ get all the promotion cases >>for that P as well. Anything less simply doesn't work. >> >>For krpkr, you need krnkr, krbkr, krrkr and kqrkr. If any are missing, >>it will screw things up. > >Someone wrote a fix for this and it was posted in the Crafty mailing list...I >haven't payed much attention to whether it works always/sometimes/never, or >whether it works very well, but it *seemed* to solve the problem. >It'll make Crafty drop out of TBs if there is a good promotion move, but there >is no TB for the promotion. > >Jeremiah It isn't simple, because I do things like stop the extra parallel threads when in a tablebase position, etc. Searching the odd promotions would take a little thought as we would want those threads back.. And the main point is, _why_? Because it will screw up the normal search since a P on the board says mate in N, but a Q on the board doesn't say mate. This means a search from a position where the promotion can be forced many plies into the tree looks like a bad move to the search. Again, get 'em all, or don't get the P database in question...
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