Author: Robert Hyatt
Date: 09:16:08 01/24/00
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On January 24, 2000 at 04:53:34, David Blackman wrote: >On January 23, 2000 at 10:07:36, Robert Hyatt wrote: > >>>>reaching a depth of 14 plies should hide most horizon effect problems from >>>>any but the very strong tactical players. But getting to 14 plies sounds >>>>impossible for a primitive program, without some sort of selectiveness... >>>>and _that_ will certainly cause tactical oversights... > >Really heavy null move pruning. That causes a few problems, both tactical and >positional. But i also saw a couple of positions where null-move was not causing >trouble, but horizon effect was. It looked like this came up about once every >three games, so in most positions, horizon effect is not causing trouble, or is >only causing trouble too deep for me to see. > >>> >>Peter McKenzie wrote: >[D]5k2/1p5r/3pp3/p2p4/1b1P1P2/qP1Q1NP1/P1P3N1/1K6 w - - >>> >>>Its obvious to a human that after Qxh7?? Bc3, white will be mated. The tricky >>>thing for a program is to wade thru. the mindless checks by the white queen, >>>and of course the null movers have a little trouble with the Qb2# threat. >>> >>>I think a vanilla 14ply null mover without any extensions would have a tough >>>time avoiding Qxh7 though - even at depth 14. >> >>I think a 14 ply search will see this. It takes Crafty 10 plies to see >>Qxh7 drop to draw, and it drops every move after that. At depth=10 Crafty >>switches to something else. I would expect a 14 ply search to get a 'sniff' >>of this... > >Looks like it's 16 ply with the black king finally finding safety on a6. Simple >check extensions fix this of course. Doing checks and check evasion in >quiescence would also help. > >For some reason, i'm finding that check extension is costing a LOT of depth at >the moment, so i don't want to put it back in until i figure out why. With older >versions of the program, check extension hardly cost anything at all, so it was >the one extension that all versions did, until December last year. > >>And yes, some positions with no extensions will look ugly... but think of all >>the good positional things a 14 ply search would see.. > >That's what i thought, until i saw it lose game after game to Crafty. But it can >certainly be tuned more ... Just make sure you know why it is losing. IE is it getting into positions where all the check extensions in the world can't save you. or are you getting int reasonable positions and then overlooking some tactical shot that you ought to find?
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