Author: Robert Hyatt
Date: 13:16:47 03/10/01
Go up one level in this thread
On March 10, 2001 at 10:41:18, Uri Blass wrote: >On March 10, 2001 at 10:05:04, Robert Hyatt wrote: > >>On March 10, 2001 at 03:34:19, Uri Blass wrote: >> >>>On March 10, 2001 at 02:55:29, Dann Corbit wrote: >>> >>>>On March 10, 2001 at 00:26:57, Michael Fuhrmann wrote: >>>> >>>>>[D] 8/8/7P/5kP1/5P2/r7/5K2/8 b - - 0 114 >>>>> >>>>> >>>>>Crafty scores this as -3.26 for white on my computer, yet it seems to be a draw. >>>>>I don't have all the 5-piece tbs. Is that the problem? >>>> >>>>I have the complete 5 piece tablebase file set. It does not seem to help much. >>>>However, it is clear that it is a draw. The output of the chase below is rather >>>>amusing. We might call it "I'll get that f4 pawn if it's the last thing I do!" >>>> >>>>Past the last actual search depth in plies, for each new search, it always ends >>>>in Kxf4. But each time we go one more ply (when we have actually examined the >>>>consequences of that horizon capture) it gets pushed out. It is clear that this >>>>is a draw. >>> >>>It seems that the problem is that Crafty does not look at the tablebases in the >>>last ply. >>>Maybe probing the tablebases everywhere can help Crafty to get more realistic >>>evaluation because it is not going to have wrong evaluation for KR vs KPP >>>endgames and evaluation for KR vs KPPP endgames is going to be closer to draw. >>> >>>Uri >> >> >>It isn't quite the "last ply". It is the first ply of the q-search, and I >>don't probe there as it is too expensive. Which means the goal of the search >>becomes "push the capture off to the q-search where I won't realize it is a >>draw." I have seen this in rare positions before... :) > >I understand the reason that you do it in the first ply of the q-search(in this >case it was also the last ply). > >I do not know if changing it in part of the cases can be an improvement. > >Some possible ideas: > >1)If the main line leads to tablebases position and if the difference between >the evaluation of this position with tablebases and without tablebases is big >enough then probe everywhere in the next iteration. > >2)compare evaluations with tablebases and without tablebases for 1 out of 100 >positions when you probe the tablebases. >If you get a big difference in significant part of the cases then probe the >tablebases everywhere. > >3)Start the game with probing the tablebases also in the qsearch. > >If the number of tablebases hits in the last iteration is not big enough then >continue probing the tablebases everywhere. > >Stop to probe the tablebases in the qsearch only when you get enough tablebases >hits so you are afraid from a significant reduction in speed. > >Uri You seem to have lots of good ideas/suggestions, all the time. Now I wish I could teach you C so that you can implement them. :)
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.