Author: Mike Hood
Date: 01:19:33 12/02/04
Go up one level in this thread
On December 01, 2004 at 22:07:55, P L Patodia wrote: >I put the position given by you in Chessbase 8 using Shredder 8 >Engine. I put infinite analysis and it immediately gave mate in >3. > >P L Patodia How are you performing the test? When I put Shredder 8 (default settings) on infinite analysis, Shredder stops searching after finding a mate in 5. [D] 3K1B2/2pPPp2/7R/2k2r2/7q/P2Q4/8/8 w - - 0 1 Analysis by Shredder 8: 1.Rxh4 +- (15.33) Depth: 1/1 00:00:00 1.Rxh4 +- (27.18) Depth: 1/1 00:00:00 1.Rxh4 +- (27.18) Depth: 1/1 00:00:00 1.Rxh4 Rd5 +- (27.45) Depth: 2/4 00:00:00 1.Rxh4 Rf6 +- (28.09) Depth: 2/4 00:00:00 1.Rxh4 Kb6 2.e8Q +- (29.03) Depth: 2/8 00:00:00 1.Qxf5+ Kc4 2.Rxh4+ Kb3 +- (39.48) Depth: 2/8 00:00:00 1.Qxf5+ Kc4 2.Rxh4+ Kb3 +- (39.48) Depth: 2/8 00:00:00 1.Qxf5+ Kc4 2.Rxh4+ Kb3 3.e8Q +- (39.59) Depth: 3/6 00:00:00 1.Qxf5+ Kc4 2.Rxh4+ Kb3 3.e8Q c6 +- (39.85) Depth: 4/8 00:00:00 1.Qxf5+ Kc4 2.Rxh4+ Kc3 3.e8Q c6 +- (40.12) Depth: 4/14 00:00:00 1.Qxf5+ Kc4 2.Rxh4+ Kc3 3.e8Q c6 4.Qb1 +- (40.38) Depth: 5/8 00:00:00 1.Qxf5+ Kc4 2.Rxh4+ Kb3 3.Qb1+ Kc3 4.e8Q c6 +- (40.88) Depth: 5/9 00:00:00 1.Qxf5+ Kc4 2.Kxc7 +- (40.88) Depth: 5/18 00:00:00 1.Qxf5+ Kc4 2.Rxh4+ Kc3 3.e8Q Kb3 4.Kxc7 f6 +- (41.13) Depth: 6/10 00:00:00 1.Qxf5+ Kc4 2.Rxh4+ Kc3 3.e8Q Kb2 4.Kxc7 Kb3 +- (41.63) Depth: 6/10 00:00:00 1.Qxf5+ Kc4 2.Rxh4+ Kc3 3.Qf3+ Kb2 4.Rh2+ Ka1 5.Qf1# +- (#150) Depth: 6/18 00:00:00 1.Qxf5+ Kc4 2.Rxh4+ Kc3 3.Qf3+ Kb2 4.Rh2+ Ka1 5.Qf1# +- (#5) Depth: 7/12 00:00:00 16kN 1.Qxf5+ Kc4 2.Rxh4+ Kc3 3.Qf3+ Kb2 4.Rh2+ Ka1 5.Qf1# +- (#5) Depth: 8/12 00:00:00 21kN 1.Qxf5+ Kc4 2.Rxh4+ Kc3 3.Qf3+ Kb2 4.Rh2+ Ka1 5.Qf1# +- (#5) Depth: 9/12 00:00:00 31kN On the other hand, if I use infinite analysis showing multiple lines, the mate in 3 is found, for instance: Analysis by Shredder 8: 1. +- (#3): 1.Ra6 Qd4 2.e8Q+ Kd5 3.Qee4# 2. +- (#5): 1.Rxh4 Kb6 2.Rb4+ Kc6 3.Qc3+ Kd5 4.e8Q Rf4 5.Qc5# 3. +- (#5): 1.Qxf5+ Kc4 2.Rxh4+ Kb3 3.Qf3+ Kc2 4.Rh2+ Kc1 5.Qf1# 4. +- (#5): 1.Qc2+ Kd4 2.Rxh4+ Rf4 3.e8Q Rxh4 4.Qc5+ Kd3 5.Qee3# 5. +- (#6): 1.Kxc7 Qg3+ 2.Qxg3 Kc4 3.Rc6+ Kd4 4.d8Q+ Rd5 5.e8Q f6 6.Qee3# 6. +- (#6): 1.Qc3+ Qc4 2.e8Q+ Kd5 3.Qa5+ Kd4 4.Qd2+ Qd3 5.Qee3+ Kd5 6.Qdxd3# The problem (it's arguable whether or not it's a bug) is that for some of Chessbase's major engines "infinite analysis" isn't really infinite. If only one line is being searched, the engine is still in playing mode, not analysis mode, and it stops analysing as soon as it has found a mate. This sort of behaviour is fully acceptable during a game, because "a win is a win", but it's not what you would want for an analysis.
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