Author: John Merlino
Date: 08:54:35 04/12/05
Go up one level in this thread
On April 12, 2005 at 05:15:43, chandler yergin wrote: >On April 12, 2005 at 00:23:30, John Merlino wrote: > >>On April 11, 2005 at 23:36:27, chandler yergin wrote: >> >>>On April 11, 2005 at 13:00:10, Rob Basham wrote: >>> >>>>On April 11, 2005 at 12:24:18, John Merlino wrote: >> >>>>>>New game, >>>>>>[D]2r1r2k/4R1pp/pb6/1p6/2nqN1QB/P5PP/1PB4K/5R2 w - - 0 1 >>>>>> >>>>>>Analysis by Shredder 8: <Some Analysis Snipped> >>>>>>1.Bf6 Qxf6 2.Nxf6 Bg1+ 3.Kxg1 Rg8 4.Nxg8 Nxb2 5.Qxg7# >>>>>> +- (#152) Depth: 12/42 00:00:22 7641kN >>>>>>1.Bf6 Rxe7 2.Bxd4 Rd8 3.Qh4 Ree8 4.Nc3 Re2+ 5.Nxe2 h6 6.Kh1 Rxd4 7.Rf8# >>>>>> +- (#152) Depth: 13/18 00:00:23 7840kN >>>>>>1.Bf6 Rxe7 2.Bxd4 Rd8 3.Qh4 Bxd4 4.Qxe7 Rg8 5.Rf8 Bg1+ 6.Kxg1 Nd6 7.Qxd6 b4 >>>>>>8.Rxg8+ Kxg8 9.Qd8+ Kf7 >>>>>> +- (#150) Depth: 14/40 00:00:43 15586kN >>>>>>1.Bf6 Rxe7 2.Bxd4 Rd8 3.Qh4 Bxd4 4.Qxe7 Rg8 5.Rf8 Bc5 6.Nxc5 Nd6 7.Qxd6 b4 >>>>>>8.Rxg8+ Kxg8 9.Qe6+ Kf8 10.Nd7# >>>>>> +- (#150) Depth: 15/36 00:00:43 15751kN >>>>>>1.Bf6 Rxe7 2.Bxd4 Rd8 3.Qh4 h5 4.Qxe7 Ne5 5.Qxe5 Bxd4 6.Qxh5+ Kg8 7.Bb3+ Rd5 >>>>>>8.Bxd5# >>>>>> +- (#150) Depth: 16/38 00:00:47 17089kN >>>>>>1.Bf6 Rxe7 2.Bxd4 Rce8 3.Qf5 Kg8 4.Ng5 g6 5.Qd5+ Re6 6.Rf8+ Kxf8 7.Qf3+ Ke7 >>>>>>8.Qb7+ Bc7 9.Qxc7+ Kf8 10.Qg7# >>>>>> +- (#150) Depth: 17/36 00:00:49 17858kN >>>>>> >>>>>>(, 11.04.2005) >>>>> >>>>>Shredder's output is incredibly bizarre here. The position is a Mate in 9, but >>>>>not a single PV shows mate in 9 moves (although there are mates shown in 10, 7 >>>>>and even 5 moves!??). >>>>> >>>>>Conclusion: Shredder found the best move, but did NOT conclusively find the mate >>>>>in 9. >>> >>>THe Mate in 9 is not forced; Shredder gave all the variations leading to >>>Mate after the Key Move. >>> >>>With "Best PLay" by Black it's Mate in 9. >>> >>>If Black errs.. he gets Mated sooner. >> >>I understand that, but Shredder's output still makes no sense at all. What do >>you mean by "Shredder gave all the variations leading to Mate after the Key >>Move"? > A Program evaluates every possible move at each ply depth; >that is one complete iteration. >Shredder found a Mate at ply 12, another at ply 13, another at ply 14, >another at ply 15, another at play 16 etc. > >What don't you understand? Simple -- take this PV from Shredder (which is the first one listed above): 1.Bf6 Qxf6 2.Nxf6 Bg1+ 3.Kxg1 Rg8 4.Nxg8 Nxb2 5.Qxg7# +- (#152) Depth: 12/42 00:00:22 7641kN A program should not announce a Mate for the side to move that is simply not possible with best play. If I were to stop analysis at this point and post my findings here, it would be soundly refuted by the simple fact that there is no Mate in 5 for White. It seems bizarre to me that, at depth 12, the Shredder thinks that there is a forced mate in 5 (only 9 plies away). jm
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