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Subject: Re: History Heuristic

Author: Sune Fischer

Date: 09:56:29 03/16/04

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On March 16, 2004 at 12:33:30, Robert Hyatt wrote:

>>   1> apply HH to the subtrees with that shallow (5-7 ply) remaining depth, and
>>      reset them for every other subtree, ofcourse
>>   2> apply HH to the top (5-7 ply) only
>>
>>It did not have the effect I thought it would have...
>>
>>Any ideas on the topic? Which should be doing better anyway? Or apply them both!
>>
>>Renze
>
>Neither.  At the root, before starting a brand new search (not a new iteration)
>age the counters...  IE in Crafty, in "main()" I shift the counters right 8 bits
>(divide them by 256).  This ages old history counters away over a few moves,
>without losing important values instantly...

I think it is better to rescale it once and a while if you analyze for a long
time on each move.

What happens is that the table will get filled with search information and as
the search moves into a new branch (a branch which is largely uncorrelated with
previous ones) the new search information will have to compete with the old one
and that can/will result in decreased efficiency.

If you rescale it every x nodes or so, the information keeps being fresh.

Anyway, this is what seems to produce the lowest nodes to solution numbers in my
tests.
Every man is his own best tester :)

-S.



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