Author: KarinsDad
Date: 22:36:27 07/09/99
Go up one level in this thread
On July 09, 1999 at 20:56:10, Robert Hyatt wrote: [snip] > > >None of that goes with "alpha/beta minimax depth-first". I _must_ search to >tip positions before looking at any score... And I'm not willing to bet that >searching 30+ plies deeply along selected lines will not find some way to make >this happen. Hhhmmmm. 30 plies (only 15 moves per side) would require that the pawns be relatively far advanced already or promoted to queens already. Still, it seems unlikely that if most of the pawns are already promoted to queens that the program would not have found a mate 2 ply earlier in the game when it was searching 30 ply then (or 4 ply earlier or 12 ply earlier or whatever). But, the only way to know for sure is to record it if it occurs within a given program (at least you would know that it hasn't yet occurred until it actually does). Remember minimax doesn't search "logical" lines. It searches >+all+ lines. The position I reached with 5 white queens was done instantly in >a blitz game. At the starting position both sides had _one_ queen. By the >time I did an instant 8 ply search + extensions, etc, and got to the first >call to Evaluate() I had 5 white queens, which produced a score way > +infinity >and blew me up. Hopefully, I've already taken that into account within my evaluation (the simple one, not the detailed one, see below), but I haven't tested it yet. > >I agree that it is very unlikely. But full-width searches often act like >"help-mate" searches... one side does everything right, the other side does >everything wrong, leading to very bizarre positions. I'd at least cover the >case so that it wouldn't blow up. Either by allowing 64 queens as I do now, >or by making sure no promotion is allowed if it takes me over my max limit. Always better to be safe than sorry. I have a square control mechanism which if I remember correctly, only takes into account up to 5 queens, 4 rooks, 4 bishops, 4 knights, and 2 pawns per side (the kings are considered separately). Now, since I use this for square control, obviously it is a little safer for any given square to assume this lower number of pieces (as opposed to on the entire board), but you have now gotten me thinking that maybe within a search, it is really not that safe at all. This was the square control for the non-battery square attack table, so 4 rooks max is fine, 4 bishops max is fine, and 2 pawns max is fine, but you could have upwards of 8 queens or 8 knights. I figured that this would be tough to accomplish in the search (especially the knights since not only would the program have to consider promoting to a knight, but it is real hard to maneuver a lot of knights to the proper squares so that they can all attack the same square). But, because of your example, I may have to reconsider. Thanks Robert! KarinsDad :)
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