Author: Omid David Tabibi
Date: 02:04:58 08/19/03
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On August 19, 2003 at 04:12:45, Tord Romstad wrote: >On August 19, 2003 at 02:48:36, Omid David Tabibi wrote: > >>It seems that some programs use Static Exchange Evaluation in order to prune >>losing captures in quiescence search. > >Not just some. Almost all strong programs do this, I think. > >>In the following position, an SEE will deem the move 1.Rxd7 a losing capture, and it might >>get pruned in quiescence. However, in fact this is a winning capture since Qf6 is attacked >>after 1.Rxd7. How do such programs solve these kind of problems? > >They don't (or at least most don't). On the other hand, the significant extra >speed gained >by not searching all captures help them find a lot of other tactics which they >otherwise >wouldn't have found. > >Try it yourself. I am almost certain that you will find that excluding losing >captures >from the qsearch is a big win. But a good SEE will be quite costly by itself. For example: [D]3r2k1/pp1r1qpp/2pb4/5p2/3R1P2/8/PPPR2PP/3Q2K1 w - - 0 1 My engine has information about all attacked squares, e.g., it knows that d6 is attacked by a white rook and defended by a black rook. However, I assume that an SEE should be able to find out that Rxd6 is a winning capture. This needs a more extensive processing of backed-up attacks (e.g., Rd4 is backed up by Rd2 which is backed up by Qd1, and Rd7 is backed up by Rd8). I'm afraid this is too costly a process. > >Tord
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