Author: James Swafford
Date: 04:43:13 01/29/02
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On January 29, 2002 at 00:05:01, Will Singleton wrote: >On January 28, 2002 at 23:20:45, James Swafford wrote: > >> >>Does anybody do this? I just implemented a passed pawn extension >>that extends the depth by 1 if the move was a pawn move to the >>sixth or seventh rank, and that pawn is not blocked by a pawn of >>the opposite color. >> >>The results are pretty disappointing. It really blew up my search. >>I decided to modify the implementation by saying only looking for >>pawn pushes to the seventh rank, and it still can blow up pretty >>bad. >> >>Obviously most over the board positions would not trigger this >>extension, but there are some that would blow up the search like >>mad. >> >>One thought I had is to use a fractional extension scheme. That >>may help, but I'd like to know if anybody else does this extension, >>and what mechanisms they have in place to keep the search bloat >>under control. >> >>It's interesting to note that Bruce lists five different extensions >>on his (excellent) web page; he hasn't actually written about any of >>them yet, but passed pawn isn't even listed. Hmm... >> >>Any ideas or comments? >> >>-- >>James > >Yeah, I found that extending both 6th and 7th rank was too costly in terms of >nodes. But extending just the seventh was ok, and the promo. Are you doing >passed pawns or all pawns? Depends on how "passed" is defined. My first implementation yesterday extended on any pawn move to the 6th or 7th that wasn't blocked on the same file by a pawn of the opposite color. Maybe a better idea is to look on the adjacent files as well, and not to extend if another pawn will be able to capture. -- James > >Will
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