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Subject: Re: how large should a pawn hashtable be?

Author: Tord Romstad

Date: 01:30:39 02/12/04

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On February 11, 2004 at 18:13:25, Dann Corbit wrote:

>On February 11, 2004 at 18:01:44, martin fierz wrote:
>[snip]
>>hi dann,
>>
>>i am quite aware that a normal hashtable works as you say - store a key and a
>>score. but really, i think that is a much too simplistic view of pawn structure.
>>pawns interact with pieces in complex ways, and i basically would like to store
>>the information i think important about pawns in the pawn hashtable, to retrieve
>>them quickly later. i can also imagine storing a "baseline score" for the given
>>pawn configuration. but i really want interactions with pieces too, and as i
>>can't hash scores for that, i'd have to save intermediate computations (such as
>>connected passers, or potential levers etc) in the pawn hashtable, and then use
>>them for the interaction terms.
>
>I bet it will be more expensive to store all that stuff in the hash table and
>try to reuse it than to recalulate it.

Not in my experience.  My pawn hash table contains lots of stuff similar
to what Martin describes.  I don't store any scores, just lots of pawn
structure related information which is used elsewhere in the evaluation
function.  By the way, I don't hash the position of the kings in the
pawn hash table.

Using a pawn hash table gives me a huge speedup compared to computing
everything from scratch in every single node.  See this post for some
numbers to illustrate the speedup I get with different pawn hash table
sizes:

http://chessprogramming.org/cccsearch/ccc.php?art_id=317762

Tord




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