Author: Dann Corbit
Date: 10:54:03 11/22/00
Go up one level in this thread
On November 22, 2000 at 03:53:47, Alexander Davies wrote: >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. Any move leading directly to a sure checkmate is exactly as good as any other. Computers do not care how long it takes. Very few chess playing programs find the shortest mate routinely. Only chess solvers like Chest or Problemiste do that. Any move that leads directly to a verified checkmate is a best move.
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