Author: Uri Blass
Date: 12:31:55 02/07/04
Go up one level in this thread
On February 07, 2004 at 03:04:51, Tim Foden wrote: >On February 06, 2004 at 22:46:15, Ricardo Gibert wrote: > >>On February 06, 2004 at 13:48:48, Jaime Benito de Valle Ruiz wrote: >> >>>This endgame study can be game following the sequence >>> >>>1.Bd1 g1Q 2.Bxa4 Qc1 3.Bxd7 h5 4.Be8 h4 5.Ba4 Line >>> >>>[d] 8/3p4/p6p/k2N3B/p7/K6p/PP4pP/8 w - - 0 1 >>> >>>Many engines (Fritz 8, Hiarcs 8, Ruffian 1.01) cannot win this endgame, probably >>>due to the well known null-move problem for extreme and rare positions such as >>>this. >> >>These programs have an obvious bug in their implementation of null move. They >>should not be using stalemate as a fail high for a null move. Stalemate is tempo >>dependent thing and null move mucks up the tempi. You can think of stalemate as >>an obvious sort of zugzwang. Note, that it doesn't matter which side gets >>stalemated after a null move. The stalemate should be treated as a fail low for >>the null moving side regardless. > >No, I agree with Uri here, its blacks queen move which is in Zugzwang which is >the problem. At c1 it's stopping the b4+ move, once it moves, black has lost. >The programs go for the stalemate because it's the best that they can see >because they don't see that the queen has to move. > >They key to this position seems to be that there is a strong king attack on >black... blacks king cannot move. And although b4+ is a long term threat for >mate. If a program sees this it should not use null move for black in this >position, and that would solve the problem. > >Cheers, Tim. > >[BTW GLC has no clue here, unless I turn null-move off :) This position goes in >my list of zugzwangs to be dealt with] Movei has no problem here because in endgame it is using verified null move pruning. Today it may have a problem in case of 2 zugzwangs but in case of only one zugzwang it has no problem. Uri
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.