Author: Heiner Marxen
Date: 17:09:40 08/10/01
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On August 10, 2001 at 11:44:53, leonid wrote: >Hi! > >If you like, you can solve this mate: > >[D]8/nqq1QQQ1/k1qpN2R/r1qpQ2R/bqq1N3/b3Q2Q/n3Q2K/r3QBB1 w - - > >Tthis position is actually very interesting from my point of view. On it my >initial speed (for brute force) is very bad and branching factor is worst that >usual. At least, position is not very deep to go. > >Please indicate your result. > >Thanks, >Leonid. Hello Leonid! According to Chest this is a mate in 7 moves. But for this depth it is comparatively hard to compute: 3.1 hours on a K7/600 with 30 MB hash. There are two solution moves: PV: Nxc7+ Qbxc7 Qxc7 Qxc7 Qxc7 Bc6 Nxc5+ Qxc5 Qxa7+ Qxa7 Qgxa7+ Kb5 Qaxa5# PV: Qxc7 Nc3 N6xc5+ Rxc5 Nxc5+ Qbxc5 Qxc4+ Qxc4 Bxc4+ Qcb5 Qcb6+ Qxb6 Qxb6# The EBF is rather high (>14): # 1 0.01s 0kN 0.87 1- 0 # 2 0.01s [ 1.00] 0kN 1.00 1- 0 # 3 0.09s [ 9.00] 4kN [ 18.80] 0.99 107- 0 # 4 2.29s [ 25.44] 127kN [ 34.76] 1.22 5672- 0 # 5 32.63s [ 14.25] 1758kN [ 13.86] 1.55 94813- 0 # 6 525.09s [ 16.09] 28850kN [ 16.41] 1.92 1475199- 689537 # 7 11112.36s [ 21.16] 628820kN [ 21.80] 1.87 33822787- 33036356 More hash would help the last depth, but not that much. Up to now you have posted only one position which has been nearly equally expensive at depth 7: Posted by leonid on February 09, 2001 at 06:51:15: [D]1bqQBnRn/3N2Qb/Q1QN2np/1Q1Q1qpk/4Qqbn/2B1Qrnn/2Q5/K1R5 w - - PV: Qxg5+ Nxg5 Qdxf5 Nhxf5 Qh2+ Bh3 Nf6+ Kh4 Qxh6+ Nxh6 Q4xf4+ Ng4 Qfxg5# Again, the PV contains a non-checking move. Also, in both cases, black has not much active counter play, and so the tree has a not so small EBF. That a mate in 4 costs more than 2 seconds is quite exceptional, also. That the board looks like a large "PD" is intended, I suspect :-) Does that mean something? Cheers, Heiner
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