Author: Robert Hyatt
Date: 06:47:14 02/28/06
Go up one level in this thread
On February 27, 2006 at 23:05:09, Uri Blass wrote: >On February 27, 2006 at 22:11:07, Robert Hyatt wrote: > >>On February 27, 2006 at 20:09:57, Uri Blass wrote: >> >>>On February 27, 2006 at 14:53:26, Robert Hyatt wrote: >>> >>>>This will be relatively short and sweet. >>>> >>>>As most know, I've been doing some major revisions to Crafty, preparing for the >>>>next WCCC event. These revisions are affecting the evaluation code which has >>>>been really ripped asunder and partially restored to sanity, and the search >>>>which includes some new reduction code replacing the older futility pruning done >>>>near the frontier, where the reduction stuff is done almost everywhere. >>>> >>>>I knew there would be a few eval issues as king safety has mainly been >>>>simplified with a couple of glaring holes left open for later work. I was >>>>really interested in the new search code because the speed/depth looked very >>>>good. >>>> >>>>So I'll start there, briefly. I've tested the new code in lots of nunn-type >>>>matches, as well as in test suites. So far, the new search solves every >>>>tactical suite I have tried in less total time than previous versions, which was >>>>surprising since the late move reduction idea often delays tactical solutions by >>>>hiding some strange threat moves that get reduced and therefore look >>>>ineffective. But happily, it has gotten better tactically in the same time >>>>frame. Yes it might take an extra ply or two to find the key move, but it is >>>>getting those 1-2 extra plies done more quickly so that the key move is _still_ >>>>found faster than the older versions. So that looks good (so far). >>>> >>>>Another thing I watched for was for a sudden "fail low" to pop up unexpectedly >>>>in a game, and I didn't see a one. Yes we had fail lows, but they were >>>>progressive and were the result of bad positions getting worse, not being +1 and >>>>suddenly seeing -3 after our opponent made an unexpected move. So for the >>>>moment, the current search appears to be solid. I have spent a ton of time on >>>>it in past weeks running test matches against older versions, running test >>>>suites and going over the output carefully, etc. >>>> >>>>Now I'm back to finishing up the eval. >>>> >>>>If you look at the Rascal game (round 8 I think) Crafty played a really lousy >>>>move 28. Nh7+. After looking at this a bit, white has two choices. The knight >>>>must move (attacked by pawn) and it can retreat to f3 (sane) or check on h7 and >>>>get trapped (insane). >>> >>> >>>I agree that 28.Nh7+ was probably not good but the knight does not get >>>trapped(it only cannot move from that square but black has no way to capture >>>it). >>> >>>I see no forced line that win material for black and crafty drew the game. >>> >>>Many programs including commercial programs have positive score for white after >>>Nh7+. >>> >>>Note that I say that Nh7+ is probably not good because I am not sure about it >>>and it is possible that there is something that I do not see and deep search can >>>get the knight out of h7. >>> >>>Uri >> >>The problem is that the move is simply lousy. White now becomes preoccupied >>with not losing the knight, and dissipates the rather significant positional >>edge he had before doing that... One doesn't have to lose material for a move >>to be lousy, one can also simply create a bind that was avoidable, as happened >>here. Things would have been oh so much simpler if the knight was in the game, >>rather than being the game... > >I agree that the move seems bad to me and I expect no human even at 1600 level >to play it(It is not a proof that it is bad because there may be a tactical >reason that it is good that both me and chess programs do not see but of course >I assume it is bad unless something else is proved). > >I respond mainly because of the word trapped: >"or check on h7 and get trapped (insane)". > >It may be misunderstanding of the english language but my understanding of the >word trapped is that it is impossible to save it and it is not clear that white >is losing the knight(maybe it is the case based on a very deep search but it is >not clear). > >Uri I think the two terms you are somewhat confusing are "trapped" and "lost". trapped means somehow the piece can't "get out" and participate. lost means it will be captured eventually. I don't know whether there is a long-range plan to win the knight once it reaches h7, as I haven't studied it that intensively. However, there is no real tactical reason to play it, other than to drive the king to the e-file, and with so little material left on the board, an attack is not going to work, so that is futile...
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