Author: Alvaro Jose Povoa Cardoso
Date: 13:48:32 10/12/01
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On October 12, 2001 at 14:05:50, Robert Hyatt wrote: >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... I understand the replacement part. What I meant was: when I read from the hash table at the top of the search and if the hash position match the current position I still want to check if the hash position is worth being considered. In the depth-preferred scheme I do this by checking if the hash draft is greater than the current draft. But in the subtree node count scheme I simply don't have the current subtree node count because I haven't searched anything yet. It is this part that puzzles me. Alvaro Cardoso
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