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Subject: Re: questions about book learning

Author: Robert Hyatt

Date: 20:46:10 01/03/04

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On January 03, 2004 at 21:22:51, K. Burcham wrote:

>I am not sure how this book learning works for each book move.
>The value that is changed, is this only because of the loss?
>Is the program using positional values once out of book to change the learned

Here is a thumbnail of what I do.

1.  Crafty remembers the evaluations for the first 10 moves out of book,
after each search has been completed.  It uses these evaluations to detect
a "trend".  IE is the evaluation good and getting better?  Is it bad and
getting worse?  Is it good but dropping (ie it grabbed a gambit pawn and
is beginning to see that it was bad) or is it bad but getting better (IE it
offered a gambit, the opponent took it, and the score is going up).

It factors all of that together and marks the book line as good or bad.

2.  Crafty takes the result of a game when it loses, and updates the book
line so that moves tried near the end of the line simply don't get played,
and alternatives near the front of the book line get tried next.

There is more to it than that, and you can look at the crafty.doc file to
at least see what I am doing in more detail.  It is _very_ effective.

>Lets say e4 is the most solid, dependable first move.
>Lets say we lose 25 games with e4.
>now we have a learned value for something.
>Is this learned value only for e4?
>Is this learned value only for the first move, regardlesss of the line played?

For me, the entire line gets some "learning adjustment".  The closer to the
first move, the "smaller" the adjustment.

>If program A plays d4 against program B and wins 25 games.
>If program A plays d4 against program C and loses 25 games.
>If program C plays d4 against program B and loses 25 games.
>I am not sure how this helps the high level book.

The danger is that you are not learning about the "book", but about
the "engines".  That is a problem.  Fortunately, it is not that common.

>Is all this learning for only the first book move?

No.  Crafty learns for _all_ moves along a line that was played.

In fact, if you beat it with a line, you can expect to play against that
line when you change colors and play it again.  :)


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