Author: Robert Hyatt
Date: 12:17:16 10/03/01
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On October 02, 2001 at 14:05:27, Frank Schneider wrote: >On October 01, 2001 at 14:46:27, Steve Maughan wrote: > >>I've been tinkering with my engine again and delved into the move ordering. >>Currently I use pseudo SEE to order i.e. if no defenders then >>value=captured_piece_value otherwise assume that value=captured_piece_value - >>attacking_piece_value. Quite simple and quick. >> >>Now I am wanting to implement SEE. I've already done this in a program I wrote >>a couple of years ago. That implementation performed a normal search where the >>only moves played were those that captured on the specific square. This was >>slow - although not horrendous. I was thinking about trying to implement >>something a little faster. Leen Ameraal posted a simple routine that utilied a >>table of attackers and defenders. Once this table is filled the actual >>evaluation is relatively quick. I'm quite sure that this would be faster than >>my original implementation. However it is clearly not a simple task to fill >>these tables. >> >>Here's a test position. Assume that White must evaluate the score of a) bxc6 and >>then b) Rxe2 >> >>[d]6k1/1p6/2n5/1P6/B7/4p3/1R1rp2R/K7 w - - 0 1 >> >>To evaluate bxc6 correctly one needs to see that the Bishop has a valid xray >>attack. Does everyone bother with this type of situation? I would imagine that >>this is quite important so I would guess that they do. >> >>The second position is a little more subtle. To see that Rxe2 wins a pawn one >>must also see that after Black recaptures on e2, white is then, and only then, >>able to recapture on e2. This is a little more subtle as it's the Black piece >>(i.e. opponents piece) that blocks the recapture. This would be (more) >>difficult to catch in a SEE routine. How many programs would evaluate this >>correctly? >> >>I suspect most do 'a' but not 'b'. > >Gromit does both. > >Who evaluates promotions in SEE correctly? > >Frank > > I used to, but I decided it was not worth it. If the promoted pawn itself gets captured, it is a non-issue if you count it as 1 on the 8th rank and then remove it as a pawn (1) as well. If it is left, then it also doesn't really matter. If it ends up a 1 (pawn) on the 8th, then you won the series of captures most likely since pawns are used before anything else. And whether you got +3 for PxB, or +11 for PxB=Q really won't affect much... I removed that a long while back and speeded the SEE code up a couple of percent without hurting the tree that I could find... >> >>All help appreciated! >> >>Steve Maughan
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