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Subject: Re: Alpha-Beta Window

Author: Robert Hyatt

Date: 15:53:02 01/18/99

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On January 18, 1999 at 17:18:12, Pauli Misikangas wrote:

>Hi all!
>
>I'm trying to optimize the size of the alpha-beta window for my shogi program. I
>understand that if I use a small window, the search terminates faster but
>re-searches (with full window) are needed more often. On the other hand,
>re-search is not so bad because I should get some useful values from the
>transposition table, right? So, what would be a good hit/re-search balance?
>
>Do you use always the same window size or change it during the game? I've been
>thinking that when nothing crucial is happening in the game (maybe during the
>opening and early middlegame) one might get some advantage by using a very
>narrow window. When the fight really begins, one could then start using a wider
>window. Do you think that this might be worth of trying? Is anybody using
>techniques like this? Is there some cases when it is better not to use
>AB-window?
>
>All the best,
>
>Pauli Misikangas
>
>Pauli.Misikangas@cs.helsinki.fi
>http://www.cs.helsinki.fi/~pmturune/index_e.html

This is a classic question that can be answered experimentally.  There is no
'holy grail' for all programs. The iteration-to-iteration swings can cause each
program to have different.

Try it with different windows, over a large test of positions, and just pick the
window that works best (produces the fastest time-to-depth.)  One trick..  watch
your odd/even score swings (if you have them).  And if you see them in your
program, anticipate by correcting the window so that the odd/even swings don't
take you over the edge too frequently...



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