Author: Dieter Buerssner
Date: 13:18:15 03/16/01
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On March 16, 2001 at 16:09:53, Dann Corbit wrote: >On March 16, 2001 at 16:02:20, John Hatcher wrote: > >>Here is a position arising from Rueben Fine's "Basic Chess Endings", No. 309b - >> >>r7/4P1k1/3K4/8/8/8/8/5R2 w >> >>White wins after 1. Ra1. This solution was found instantly (of course) by both >>Wcrafty-18.6 (using Winboard) and Fritz6, both using the same 5-piece Nalimov >>tablebases. >> >>But now it gets strange. What if White temporizes first with 1. Rg1+ Kf7, >>arising at this position: >> >>r7/4Pk2/3K4/8/8/8/8/6R1 w >> >>Wcrafty-18.6 instantly finds the win after 2. Rf1+ Kg7 (not 2. ...Ke8? 3. Rf8#) >>3. Ra1, transposing into the first position. However, Fritz6 doesn't see the >>win!? It's engine output reads: [...] >>How can Fritz6 see the win in the first position and not see it in the second? >>The most obvious move, 2. Rf1+, isn't even listed in the engine output!? >> >>What's going on here? Can anyone duplicate this strange output? > >That is very odd. Every engine I tested (which knows about tablebase files) >found it immediately. > >I have the 5 men files. Maybe Fritz has only the 4 men files available? I don't think, this is the reason. For the above positions current versions of Yace disable access to 5-men TBs with my set of TBs (KRPKR without any promotion cases). Nevertheless the right move is found instantly with big score. First, I would have thought, that missing promotion cases may be a problem for Fritz, but in both positions, the correct move is not a promotion move, and so this seems not a logical explaination. These position would not suffer (yet) from the well-known problem with the missing promotion cases. -- Dieter
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