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Subject: Re: evaluation tuning tricks

Author: Fabien Letouzey

Date: 08:13:28 03/17/04

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On March 17, 2004 at 11:08:24, Uri Blass wrote:

>On March 17, 2004 at 11:04:20, Fabien Letouzey wrote:
>
>>On March 17, 2004 at 10:27:34, Tom Likens wrote:
>>
>>>On March 17, 2004 at 09:52:27, Tord Romstad wrote:
>>>
>>>>On March 17, 2004 at 04:58:06, Peter Alloysius wrote:
>>>>
>>>>>what are tricks for evaluation tuning so that it could
>>>>>search less nodes?
>>>>
>>>>An easy way to reduce your tree size enormously is to evaluate all
>>>>positions to the value 0.  You will get beta cutoffs at the first move
>>>>everywhere in the tree, therefore the tree will be extremely small.  Your
>>>>move ordering will always be perfect, and the simple evaluation function
>>>>will certainly boost your nodes/second count.  :-)
>>>>
>>>>Seriously, I don't think tuning the evaluation is the right way to go
>>>>in order to reduce the tree size.  You should rather concentrate on
>>>>making the evaluation function as accurate as possible, and look for
>>>>improvements in your search and move ordering when trying to reduce the
>>>>size of your tree.
>>>>
>>>>Tord
>>>
>>>Ah ha!!  I knew there was a final *secret* you weren't sharing Tord, but now the
>>>cat is out of
>>>the bag.  After reading this I've replaced my evaluation function completely
>>>with...
>>>
>>>return 0;
>>>
>>>and it has *never* been faster.
>>>
>>>--tom
>>>
>>
>>
>>That's only the beginning.
>>
>>Now that the first move always gives the best score, you don't need to search
>>the other ones anymore ...
>>
>>There are many secrets you did not know about apparently!
>>
>>Fabien.
>
>There is only one problem
>
>evaluating mate position as 0.00 is not a very good idea for results and if your
>0.00 is for every position except mates then you cannot be sure that the first
>move always give the best score.
>
>Uri


I know Uri (you can check in my search_mate.cpp), but the joke would not work
anymore if I had to explain that special case.

Fabien.




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