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Subject: Re: The Limits of Positional Knowledge

Author: Bas Hamstra

Date: 07:15:22 11/11/99

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Hello Michael,

Very interesting subject. I can can tell you that modifying eval, even minor
changes can affect playing strength pretty much. I can beat GNU most of the
time, but when I set for example centre controle somewhat lower it walks right
over my program. It matters a lot in my opinion.

Can it play a strong game with only pawn structure, king safety and piece
advancement, for example? Just don't allow pieces on my half of the board. Well,
no. You have to do something I call "activety". Rooks connected, on open files,
no knights on edge etc. But if you go too far it takes too much cycles, and
search less deep. I'm wrestling with it too. But that a well tuned eval is very
important is out of the question for me. Now I am going to read the other
replies to your post first.

Regards,
Bas Hamstra.



On November 11, 1999 at 03:37:10, Michael Neish wrote:

>
>Hello,
>
>I sent in a question to rec.games.chess.computer a while ago about how best to
>improve a newly-written Chess program, either by sharpening up its search
>routine or by programming a better positional sense.  In reply I was recommended
>to study the available source code for ideas.
>
>This has led me to another question.  Supposing you stubbornly insist on using
>alpha-beta, and not add any of the sophisticated embellishments that everyone
>talks about (killer move, null move, etc).  How far can you expect to go just on
>programming positional sense alone?  I ask this because it seems to me (as
>someone mentioned only last week on rgcc) that positional sense in a program is
>to a large extent only window dressing, and that the strength in a program lies
>mainly in its ability to search deep.  From my meagre experience as a Chess
>programmer it seems to me that positional sense provides nothing more than
>general pointers to the program to play sensibly.
>
>To Dr. Hyatt, who was one of those who replied to me: have you ever tried
>feeding nonsensical positional variables to Crafty to see how its play is
>affected?  Okay, maybe nonsensical values will ruin the evaluation function
>completely (like a value of 5,000 for putting the Queen on a1) but what about
>different weighting values from the one you use in Crafty, but still sensible?
>Won't the values that enable Crafty to search for the right move in one position
>be useless (or detrimental) in other positions?  What difference can it make for
>the Bishop to get a score of 32 instead of 30 for landing on e4?  Wouldn't
>incurring a heavy penalty for moving, say, Pawn to h5 in a front of your castled
>King prevent Crafty from playing h5 when it would be correct to do so?  You will
>of course excuse me for not having studied every single line of Crafty's code.
>:)
>
>Thanks for your time.
>
>Mike.



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