Author: Robert Hyatt
Date: 19:11:07 02/27/06
Go up one level in this thread
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...
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