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Subject: Re: statistics and move ordering

Author: Steffen Jakob

Date: 09:11:59 08/10/98

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Hi Ed!

On August 10, 1998 at 07:59:15, Ed Schröder wrote:

>>I would like to tell you something about an idea which I had this
>>weekend. I talked a bit about it with Bruce at ICC and he said that it
>>might already be a known idea. I would appreciate some feedback.
>
>>Some time ago someone (KK?) posted statistics about the first moves of
>>white. This seemed rather useless for me. More interesting would be
>>the the likelihood of _any_ move played in a won game by a strong
>>player. This information e.g. could be used for a trivial move
>>ordering. My plan is to do the following:
>
>>1. Use a precalculated list of all possible moves for the move
>>   generator in your chess engine.
>>2. Add a counter to the move structure
>>3. scan a large database with only high quality games and
>>   increment the counter for each game where the winner made this
>>   move.
>
>You will find the idea in Rebel10. It will be an option as I don't know
>if it makes the program stronger or weaker. The idea goes further in
>respect that results found in the database are subject to the Rebel score.

Could please tell us a bit more about this option? Do you consider any moves of
the database or only moves in "similar" positions? There are two extremes:

(1) consider moves of any position
(2) consider moves of exact the same position

Disadvantage of (1) is that most moves which lead to a bonus or penalty dont
have anything to do with the current position of the game. Disadvantage of (2)
is obvious. Between (1) and (2) there can be done a lot. Some ideas:

- count moves of positions with the same pawn structure
- count moves of positions with the same material
- count moves of positions which match a certain (maybe CHE-like) pattern
- count moves of positions where the same number of moves were made

>For every move found in the database Rebel will give a flexible bonus or
>penalty based on the percentage and average ELO found in the database.
>
>In this way it is the database who will guide Rebel which move to play.
>Blunders are automatically filtered because the search will decide after
>all.

Do you use the bonus/penalty also for the move ordering? :-)

>>The counter could be used to perform a very simple but also cheap move
>>ordering or even for the evaluation itself. This idea could be improved
>>if you don't store only a counter but a set of (pawnstruct, counter)
>>pairs.

Greetings,
Steffen.



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