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Subject: Re: Fixed

Author: Vincent Diepeveen

Date: 16:28:42 02/20/02

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On February 20, 2002 at 16:10:01, Frank Phillips wrote:

>On February 20, 2002 at 12:48:06, Steve Maughan wrote:
>
>>Thanks for the help everyone!
>>
>>I've implemented the idea I outlined and this has fixed the problem.  However
>>effectively I ignore possition where I cannot add a hash entry without
>>overwriting another.  This means that there is currently the possibility of a
>>draw not being detected.  I'll probably test a rehashing mechanism.
>>
>>Regards,
>>
>>Steve
>
>Just stick the entry in the next available slot (that has a hash signature of
>zero).  The debug tests I did never showed more than a few re-hashes - once it
>was working properly.
>
>I changed to this method from a simple array list following Bruce's description,
>because it seemed so elegant with the possibility of speeding up detection in
>the endgame - when the list approach might have many entries to check.
>
>After falling for the obvious trap of not always removing an entry when exiting
>ABsearch() early, it seems to work fine.
>
>I noticed no significant speed loss (or speed up) in the short middle game test
>I use.
>
>Frank

You measured pretty bad then depending upon hashtable size. An array
that gets read within 1 cache line and is already within L1 or L2
is kicking the hell out of this hashtable approach.



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