Author: Uri Blass
Date: 07:30:11 01/09/04
Go up one level in this thread
On January 09, 2004 at 09:58:54, Robert Hyatt wrote: >On January 09, 2004 at 05:36:57, Sune Fischer wrote: > >> >>>>>I hope the 2 statements above are sound. >>>>> >>>>>The next part of my argument is I think you only 3-4 entries in the array, and >>>>>you dont need to iterate all pieces, just the first 1 or 2 captures each >>>>>(depending how you count them - and if you count the first one or not). >>>>> >>>>> >>>>>after the initial capture, the other side either has a good capture, or they >>>>>dont. To determine if there is a good capture or not, I dont see that we need to >>>>>pile a nearly unlmited number of pieces on. The minimax could would need a >>>>>slight tweak to disregard the last capture I think. >> >>You can make the sequence shorter if you only want to know if it's a winner or >>loser, but not if you want to know how much it wins or loses (AFAICT). >> >>E.g. PxQ is clearly a winner so we can stop right there, but do we lose the pawn >>or not? >> >>I had this check in at one point, you just need to see that your current gain is >>higher than the value of the last piece you captured with, so even if you stand >>to lose that you are still ahead. >> > >I do this in my q-search now. If a piece captures a piece of equal or less >value, I use SEE to analyze the expected gain/loss. If a piece captures a >piece of greater value, I just assume the gain is captured - capturing and >skip SEE to save time. > > > > >>>I also noticed that the order of using sliding pieces, say rooks can matter, and >>>crafty chooses them randomly. Say one Rook reveals no hidden attacker, and the >>>other reveals a Rook, OR, one reveals a Q, and one reveals a R, this must surely >>>have an outcome that would be different if you randomly selected the other rook >>>to start with. or maybe there is no difference, as it is unlikely to be a >>>smaller piece, which is the only case that upsets the apple cart. Larger >>>revealed pieces dont change the order at all, they go to the end of the queue, >>>even reveals pieces (rook reveal rook) dont change the order either. A Rook can >>>only reveal rooks or queen, bishops can only reveal bishops or queen, the queen >>>is the only piece that can reveal smaller pieces, and it is unlikely to have 2 >>>Queens in which that is the only case you can reveal a smaller piece. So the >>>order of queens capturing is the only place where this can go wrong. >> >>The order of captures does matter actually, Rfxc3 wins a rook while Rcxc3 is >>just an equal capture. > >How can that matter? The next cycle will use the other rook and since we are >only looking at one square, the order you use rooks is immaterial. If they >uncover a queen, the queen won't be used until _both_ rooks have been used, >no matter what gets uncovered when... It is not going to change the evaluation of Rfxc3 but it may change the evaluation one ply earlier if there is a previous capture to analyze. [D]7k/2R5/8/2r5/8/2p2r2/1K6/2R5 w - - 0 1 Rxc3 Rfxc3 wins a rook for a pawn for black when Rxc3 Rcxc3 wins a pawn for white. If you are unlucky to search Rcxc3 in your see then you may consider the capture as a good capture. Uri
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