Author: Robert Hyatt
Date: 18:57:15 03/10/01
Go up one level in this thread
On March 10, 2001 at 17:07:33, Uri Blass wrote: >On March 10, 2001 at 16:16:47, Robert Hyatt wrote: > >>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. :) > >I learned C but I never wrote big programs in C of more than some hundreds >lines. > >Uri Break out the C book and get busy. :)
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