Author: Heiner Marxen
Date: 14:46:51 04/17/01
Go up one level in this thread
On April 17, 2001 at 14:45:49, Tim Foden wrote: >On April 17, 2001 at 11:13:02, Heiner Marxen wrote: > >>On April 17, 2001 at 07:43:30, leonid wrote: >> >>>Hello! >>> >>>If you like to solve very "regular" mate position, then you have one. >>> >>>[D]R7/4P1Pq/1rR5/2pb1rnk/1Q3B2/4Nn2/1PB2Np1/2K1b1Q1 w - - >>> >>>Please, indicate your result. >>> >>>Thanks, >>>Leonid. >> >>According to Chest there are two key moves for mate in 7 moves: >> >>Qxg2 Bd2+ Qxd2 Bxc6 g8=Q Qxg8 Rxg8 Bd5 e8=Q+ Bf7 Nxf5 Nd4 Rxg5# >>Rh8 Bd2+ Qxd2 Be4 e8=Q+ Rf7 Qxf7+ Nxf7 Qd5+ Bf5 Rxh7+ Nh6 Rhxh6# > >This is worrying to me, as Green Light thinks it finds another mate in 7, which >begins with e8=Q+ That should worry you or me, since one program has a bug, but we do not yet know which program really has the bug. >As I understand it Chest finds all the mates, doesn't it? It is supposed to do so. That is its purpose, yes. >Here is a snippet of GLC's analysis (v2.14-pr7, hash 48M, Duron 880MHz): > > 8 26.25 320.983 16660k Bd1 Bd2+ Qxd2 Rxc6 Qh2+ Kg6 e8=Q+ Bf7 Qxh7+ Kxh7 > g8=Q+ Bxg8 Qxg8+ Kh6 Nxf5+ Kh5 Qxg5# > 8 51.62 320.987 38611k e8=Q+ Bf7 Qxg2 Rxc6 Qg4+ Kg6 Qxf5+ Kh5 Qexf7+ Rg6 > Qg4+ Kh6 Nf5# <ht> > 8 55.91 320.987 42689k e8=Q+ Bf7 Qxg2 Rxc6 Qg4+ Kg6 Qxf5+ Kh5 Qexf7+ Rg6 > Qg4+ Kh6 Nf5# <ht> > 9 1:00 320.987 47464k e8=Q+ Bf7 Qxg2 Rxc6 Qg4+ Kg6 Qxf5+ Kh5 Qexf7+ Rg6 > Qg4+ Kh6 Nf5# <ht> > 9 1:31 320.987 77248k e8=Q+ Bf7 Qxg2 Rxc6 Qg4+ Kg6 Qxf5+ Kh5 Qexf7+ Rg6 > Qg4+ Kh6 Nf5# <ht> > 10 1:51 320.987 96843k e8=Q+ Bf7 Qxg2 Rxc6 Qg4+ Kg6 Qxf5+ Kh5 Qexf7+ Rg6 > Qg4+ Kh6 Nf5# <ht> > >Cheers, Tim. Ok, I looked into this variant. After 1.e8=Q+ Bf7 2.Qxg2 Rxc6 we have [D]R3Q3/5bPq/2r5/2p2rnk/1Q3B2/4Nn2/1PB2NQ1/2K1b3 w - - which according to Chest indeed leaves a mate in 5, with this PV: Qg4+ Kg6 Qxf5+ Kh5 Qexf7+ Rg6 Qg4+ Kh6 Nf5# That is exactly your variant. But Chest chooses another second black move: Bd2+. After 1.e8=Q+ Bf7 2.Qxg2 Bd2+ we have [D]R3Q3/5bPq/1rR5/2p2rnk/1Q3B2/4Nn2/1PBb1NQ1/2K5 w - - and Chest does not find a mate in 5, here. Here is its refutation table: refu 1: Qxd2 Rxc6 [ 4-] solu 1: Bxe8 [ 1+] solu 2: Nxd2 [ 1+] solu 11: Nd4 [ 1+] solu 12: Ne5 [ 2+] solu 13: Ne1 [ 1+] solu 14: Ng1 [ 1+] solu 15: Qxg7 [ 1+] solu 16: Ra6 [ 1+] refu 2: Kd1 Rxc6 [ 4-] solu 3: Bxe8 [ 1+] solu 4: cxb4 [ 1+] solu 5: Bxb4 [ 1+] solu 6: Rxb4 [ 1+] solu 17: Ne4 [ 1+] solu 18: Rd5 [ 1+] solu 19: Nh3 [ 1+] solu 20: Ra6 [ 1+] refu 3: Kb1 Rxc6 [ 4-] solu 7: Bxe8 [ 1+] solu 8: cxb4 [ 1+] solu 9: Bxb4 [ 1+] solu 10: Rxb4 [ 1+] solu 21: Ne4 [ 1+] solu 22: Ra6 [ 1+] solu 23: Qxg7 [ 1+] Hope this helps you to pin this down further. If you still find a short enough mate, here, please post it, and I will answer with the variant Chest uses to refute it. In the end we will see who errs, when the mates become short enough that we poor humans see it ourselves. Heiner
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