Author: Bas Hamstra
Date: 05:29:28 03/05/01
Go up one level in this thread
On March 05, 2001 at 07:26:28, Leen Ammeraal wrote: >I understand that it is usual to have at most >one entry in a hashtable for a given position. >Clearly, an entry with a higher (depth) draft >should replace one with a lower draft, >while a new candidate with a lower draft >should be ignored. >Therefore, in the rest of this discussion, >let us assume that the draft >of the existing entry is equal to that of >the entry that may replace the older one. >It seems clear to me that a tighter bound (higher >value in the case of LOWER and a lower value >in the case of UPPER) should have precedence. >If a lower bound has been stored and >the new candidate is an upper bound >with the same score, then I replace the LOWER >flag with the EXACT flag. >The situation is similar with lower and upper >exchanged in the last sentence. >But what if these scores are unequal? >Is a lower bound more valuable than an >upper bound, or is it the other way round? >Remember, we are talking about equal draft, >unequal scores and one flag being LOWER and >the other UPPER. >Leen What I do in case of equal draft is simply replace the older one, without any further consideration. Almost all records are bounds. Purpose of alphabeta is to move alpha up and beta down, until they intersect. Basically it's the same thing. One important difference, though, is that LOWER type hashrecords have a useable bestmove and UPPER type not. Bas.
This page took 0.02 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.