Author: Tord Romstad
Date: 05:33:49 11/04/03
Go up one level in this thread
On November 04, 2003 at 06:42:56, scott farrell wrote: >Consider the position below, just moving into the qSearch my engine tries the 2 >checks, and RxP. > >The checks lead to a qsearch for white that looses the rook. Does this mean that you search checks like Rb1+ and Ra2+ in your qsearch? I did this before, but removing checks which lose material from the qsearch was a big improvement for me. >The RxP leads to a qsearch for white of the promotion. > >Clearly it doesnt like any of these moves, so it just takes the stand-pat at the >node it is at. As such it is horizoning the fatalities in the qsearch. > >Is this correct? Yes, I think so. >How many people use stand-pat ala crafty? Who uses what else? My engine does like Crafty. >even though my engine has the pawn promotion in the qSearch, the stand-pat >stops it from playing it. I try to solve such problems with my evaluation function. A passed pawn on the 7th which can safely advance and promote (I check this by calling my SEE from within the evaluation function) is given a huge bonus. My engine will not want to stand pat in the position you use as an example, because the static eval returns a very bad score (-5.43). > >A 1 depth search from this node, gives me 75 nodes, and the score drops by 5 for >black. > >One solution I can see is to staticly evaluate the rook as lost, so it wont >stand-pat at the node. My evaluate function doesnt really consider who's move it >is, to see the rook is undefended and under attack, and sideToMove is going to >allow its capture. I have some eval code for pinned pieces and enpris and the >like, but low values - it would seem to me here I could statically say the Rook >is lost. I don't think this is a good idea. That black's rook is hanging is not really very relevant here. You could move the black rook to almost any other square on the board, and black would still be lost. >The only other solution I can think is to let the other side make its qsearch >moves anyway, sort of like null-move, and given they all fail-high for white, >dont allow the stand pat or something (sort of like dont allow stand-pat during >checks). I haven't tried this, but it sounds rather expensive. The best idea might be to take a close look at your passed pawn evaluation. Two connected passed pawns on the 7th rank should be evaluated as being worth more than a rook, IMHO. Tord
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