Author: Alexander Davies
Date: 00:53:47 11/22/00
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On November 21, 2000 at 03:38:39, Dann Corbit wrote: >On November 21, 2000 at 03:36:38, Jeremiah Penery wrote: > >>On November 21, 2000 at 03:21:54, Dann Corbit wrote: >> >>>I have a machine with lots of memory and lots of tablebase files. Running >>>ExChess 4.01 on that machine with 100 megs hash and all 5 + some 6 piece >>>tablebase files gave this: >>> >>>[D]1k6/5RP1/1P6/1K6/6r1/8/8/8 w - - bm Ka5 Kc5; id "WAC.041"; >> >>It appears that b7 is a mate in 18. >> >>19-> 1:34 Mat18 1. b7 Rg5+ 2. Kc6 Rg6+ 3. Kd5 Rg5+ >> 4. Ke6 Rg6+ 5. Kf5 Rg1 6. Rf8+ Kxb7 >> <HT> >> >>It first found mate in 23, then 21, 20, and 18. So it could go down again, but >>I doubt it. >> >>However, Ka5 seems to be a mate in 15, and Kc5 a mate in 17. >> >>15-> 1:14 Mat15 1. Ka5 Rg1 2. Rf8+ Kb7 3. g8=Q Ra1+ >> 4. Kb4 Rb1+ 5. Qb3 Rxb3+ <HT> >> >>15-> 1:06 Mat17 1. Kc5 Rg5+ 2. Kb4 Rg4+ 3. Ka5 Rg1 >> 4. Rf8+ Kb7 5. g8=Q <HT> > >In any case, b7 must be added. Any move that provably leads to checkmate is >just as good or better than any other choice. > >The EPD test suite must be amended. If your program chooses b7, that is a >correct choice. Reinfeld: "White can win with 1.b7 and then moving his King to the King-side in reply to repeated checks; or he can win by moving his King at once. He must beware of 1.Rf8+ Kb7 2.g8=Q? Rxg8 3.Rxg8 and Black is stalemated." In other words, Reinfeld gives the solution as 1.b7, 1.Ka5 or 1.Kc5. From a human point of view, they're all good - WAC was designed for players below about 1400. Reinfeld's original intention here does not apply; only a program with a bug is going to fall for the stalemate. For computers, only 1.Ka5 should be considered the correct solution, assuming it is the quickest mate. Alex Davies
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