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Subject: Re: Why not store both a lower and an upper bound in a hashtable?

Author: Leen Ammeraal

Date: 22:32:10 12/06/00

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On December 06, 2000 at 20:43:30, J. Wesley Cleveland wrote:

>On December 06, 2000 at 12:45:30, Leen Ammeraal wrote:
>
>>I have the impression that most chess programmers
>>use their hashtables to store
>>only one evaluation value, along with a flag
>>denoting Lower, Upper, or Exact.
>>Why not store both a lower and an upper bound,
>>where lower = -inf or upper = +inf if only one
>>real bound is available? A flag is then
>>superfluous, since this follows from
>>the two bound values.
>>For example:
>>LB      UB     Flag value (not stored)
>>-inf    100    Upper
>>-20     +inf   Lower
>>30      30     Exact
>>This also offers the possibility to store
>>two different bounds at the same time, as in
>>LB = -50, UB = 70.
>
>There may be a problem here. What do you do when you have a upper bound and a
>lower bound with different depths? Crafty appears to store these in two
>different hash table entries.

Thank you. Yes, I already had the impression that something
might be wrong with the depths, but taking two different
entries solves this problem. I think I will revise my
hash table.

Leen






>
>>Leen Ammeraal



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