Author: Frederik Tack
Date: 12:24:19 11/17/05
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On November 17, 2005 at 02:31:43, Tony Werten wrote: >On November 16, 2005 at 15:18:56, Frederik Tack wrote: > >> >>I actually followed you advice and tested it out. I am surprised in the sense >>that it happens a lot less than you and me thought. >> >>In a typical opening position the result was +- 0,5% of the nodes. >>In a typical midgame position (with king still in the center of the back row) >>the result was +- 1%. >>In a typical endgame position (with the king exposed in the center of the board >>and enemy rook, bishop and knight and 3 pawns on the board) the result was +- >>3%. >> >>When i think of it, these low percentages aren't so surprising at all, since the >>king captures are always put at the end of the movelist by my move generator, so >>in most cases, they are cut-off during alpha-beta search. > >I'm puzzled. Capturing a king gives an immediate cutoff. It should be searched >first. >Searching it last means you have wasted a lot of nodes. > >When you move the kingcapture forward, and then count, you will get about 25%. >It means (since you only count kingcaptures in 3%) that in 22% you have searched >part of a tree that you could have avoided. > >To me this sounds like you basicly doubled your branchingfactor, to save you >from doing InCheck. > >But maybe I'm not getting it. > >Tony > What i meant by king captures is the king capturing a piece, not the king being captured by a piece. I use a static exchange evaluator during move generation, so if a king captures a piece but will be captured on the next move by an enemy piece, the move is put at the end of the list by the SEE. The non-capture moves i also generate in a specific order (pawn moves first, king moves last (except for castling moves, since i have tested for checks in that case)). Of course moves where a piece captures a king will be sorted at the beginning of the list. Fred
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