Author: Dieter Buerssner
Date: 11:22:20 01/16/02
Go up one level in this thread
On January 15, 2002 at 21:50:52, martin fierz wrote: >i have a question about repetitions, and it's only about the search itself, not >about the game history: in my checkers program, to find repetition draws i keep >track of the hash keys of the current variation, and if i find that the key for >the current position has already ocurred before in the search, i return zero >without searching further. i think this is the standard implementation?! >anyway, i am wondering about the following problem: imagine you are searching a >variation, and in the end you make a repetition. the program will stop searching >there in the tree and assign the position a value of 0. now imagine that you >have a different path of moves without a repetition which ends up at that node, >probes the hashtable and returns 0. is this just my imagination, or can this >happen and can it be bad? A discussion of this subject can also be found in Dennis Breuker's thesis under the chapter "The Graph History Interaction problem". The thesis is downloadable at: http://members.ams.chello.nl/dbreuker/thesis/index.html Another easy to implement idea, that in some cases can help with this problem (but in no way solve it in general), is to check the hash move. If the hash move yields in repetition of position, but does not have a draw score, don't allow cutoffs. Similar problems also occure, when the game approaches draw by the 50 moves rule. Regards, Dieter
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.