Author: Tony Thomas Karippa
Date: 16:35:54 02/27/06
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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). Crafty chose the latter for lots of reasons, mostly >wrong. The king has to move to the e-file, as the g8 square is attacked by a >white bishop, and the f8 square where the king now stands is attacked by the >knight. So Crafty is pushing the black king into the center of the board. The >only problem is, queens are gone, and there is not a plethora of material >available to attack the king in the center, and in fact, with the knight stuck >at h7, nothing happens at all. This was just an evaluation error caused by >recent changes to king safety that were considered "temporary at best". I had >to reduce the king safety scores so that we could tune the other scores for >pieces and not keep seeing unusual moves that were a result of big kingsafety >swings, screwing up our ability to compare changes to see which was better. > >Another issue was that Mike/I did zero book preparation, which showed. On Sat >and again on Sunday we played a horrible Sicilian line (I think against Fruit, >then again against Glaurung) where we then played Bg7 taking the bishop out of >play, and then castling that way as well resulting in a cramped position. >Against Glaurung we actually broke the bind, but the bishop never got into the >game still and we were eventually squeezed to death. I should have warned Mike >to avoid Sicilian positions because the king safety is simply not ready yet and >it particularly gets into wild things when both sides castle opposite, which >didn't happen here. > >My next plan of attack is to take the evaluation and continue to simplify and >clean things up, and then fill in the missing holes as necessary after watching >lots of games. Crafty's endgame skills are slowly returning as other eval terms >are fixed and no longer swamp the important terms in endgames. I doubt any >parallel code will be changed unless I end up on some sort of hardware with an >unexpected "issue" that needs addressing, so until May, the Eval is going to be >the focus for the group of folks helping me work on this stuff... > >I was quite happy to not play "certain opponents" and get drowned with incessant >banter about nonsense, so that was a welcome change. :) Although we had some >of that "banter" on channel 64 frequently, but I just generally tuned channel 64 >out and enjoyed watching a couple of games along with the Crafty game... > >I believe this new version, when done, will end up being significantly stronger >than anything released in the past from the Crafty series. How it will compare >to the "front runners" will be seen in a few months, although it will >occasionally play on ICC as well. I will add that I have a "random rotation" >set up on ICC so that the most recent version does not play all the time to >avoid any tuning issues that might come up. :) I have several older versions >that now "claim" to be version 20.3, to make it more difficult to tune against >prior to the WCCC. Once the WCCC arrives, the current version will again become >public and I'll start to work on ideas for next year... That's one of the thing I like about you, you never give up, always thinks positve and continues to improve crafty. Many who started programming the same time as you have already quit, or hadnt made any progress in many years. Good luck in WCCC Professor. Tony
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