Author: chandler yergin
Date: 12:20:35 04/12/05
Go up one level in this thread
On April 12, 2005 at 11:54:35, John Merlino wrote: >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 The Program did what a Program is supposed to do! I "clipped" the analysis. Do you have any doubt, that if I had let it run,. that it would stabalize on the Mate in 9 with a deeper search?
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