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Subject: Re: Hash replacement scheme

Author: Robert Hyatt

Date: 11:05:50 10/12/01

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On October 12, 2001 at 13:55:36, Alvaro Jose Povoa Cardoso wrote:

>I red some stuff somewhere of a hash replacement scheme that uses the node count
>of the subtree bellow the node we are considering.
>It came to my mind the following:
>At the top of the search we probe the hash table for a position and we would use
>this node count to determine if the hash position should be given credit or not.
>_But_ at the top of the search we simply don't have a node count of the subtree
>bellow this node because we didn't search anything yet.
>So my question is: How do we compare the current position (wich has no subtree
>node count) with the hash position (wich has a subtree node count)?
>Using the 'draft'  instead o f the node count we don't have this problem.
>
>Any comments, please?
>
>Regards,
>Alvaro Cardoso


You don't use the node count for matching.  you use it for _replacement_.  IE
if you go to store an entry in the table, you first ask "which has the largest
node count" and you keep the one that does.  That is similar (but not identical)
to the concept of "depth-preferred replacement" that most of us use...  we keep
the entry that represents the _deepest_ search...



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