Author: Ulrich Tuerke
Date: 05:30:23 03/05/01
Go up one level in this thread
Based on bit testing, I do think that a lower bound is more valuable than an upper bound at the same depth. Perhaps, this is true, because in case of a lower bound you have in addition to the score also a best move stored in the hash entry. This is not possible for an upper bound (because there is no cutting move). So, we have more information in case of a lower bound. Uli 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
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