Author: Robert Hyatt
Date: 13:51:06 10/12/01
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On October 12, 2001 at 16:48:32, Alvaro Jose Povoa Cardoso wrote: >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 You _still_ have to check the depth before using the score. The node count is an _additional_ piece of information you use only to control the replacement policy. Not when you use the entry...
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