Author: Robert Hyatt
Date: 14:36:13 03/16/01
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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 - > >[D]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: > >[D]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: > >Analysis by Fritz 6: > >1. = (0.03): 10.e8R Rxe8 11.Rf1+ Kg6 12.Kd5 Kg5 13.Rf7 Rd8+ 14.Ke5 Re8+ >2. = (0.00): 10.Re1 >3. = (0.00): 10.Rh1 >4. = (0.00): 10.Rd1 >5. = (0.00): 10.Ke5 >6. = (0.00): 10.Kd5 > >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? > >JOHN Probably Fritz is counting a 2-fold repetition as a draw. Crafty doesn't do this quite the same way to avoid this kind of problem..
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