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From: vdhaar@natlab.research.philips.com (Haar vd P.)
Subject: Re: Writing Othello game, please advise.
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Date: Wed, 6 Mar 1996 07:50:48 GMT
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William Robert Night (wnight@vanbc.wimsey.com) wrote:

: : int strength[INDEXHI+1][INDEXHI+1] =
: : {{ 1024,    2,  256,   16,   16,  256,    2, 1024},
: :  {    2,    1,    8,    4,    4,    8,    1,    2},
: :  {  256,    8,  128,   32,   32,  128,    8,  256},
: :  {   16,    4,   32,  128,  128,   32,    4,   16},
: :  {   16,    4,   32,  128,  128,   32,    4,   16},
: :  {  256,    8,  128,   32,   32,  128,    8,  256},
: :  {    2,    1,    8,    4,    4,    8,    1,    2},
: :  { 1024,    2,  256,   16,   16,  256,    2, 1024}};

: Did you develop these weightings on your own, or are they from a book? 
: (they are similar to mine, but my weightings don't give such a high value 
: to the corner, because it tends to encourage the program to play stupidly 
: to get it.)

The first Othello program I saw and played was in Basic and had an array
that contained in ordered sequence all locations. It just chose the first
playable location in the array. Despite its simplicity, it beat me the
first few games (I was a novice at Othello at that moment). But soon I
got the hang of it and decided to write an Othello myself.

At that point, one option was to copy that method and to use the index
of the first playable location in that array as an evaluation for a move.
I guessed this would be useless as it would still require a board evaluation
to determine strategic issues. I therefore opted for a strength table
that is more extensible, but when working one ply deep would act as if
just the first playable one in an ordered list of locations were selected.

I have to agree with Patrick Leung that these strength arrays may have
limited success. I guess that the only reason it outsmarts me is that
in the last 8 moves, it does an exhaustive 8 ply deep analysis counting
stones only (I think I'll leave this in).
For the opening and middle game though, I'm thinking about revising my
evaluation, relying more on strategy.

A few issues that popped up already were
- favour pieces near corners when occupied (William Robert Night)
- stable pieces (Patrick Leung)
- frontier pieces (Patrick Leung)
- opening book (Peter van de Haar)
- increase mobility (Peter van de Haar)
- main diagonal control (Peter van de Haar)
- few pieces during opening and middle game -quiet moves- (Patrick Leung)

Anyone care to come up with more?

Peter...

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 _______________________________________
|           Peter van de Haar           |
|  vdhaar@natlab.research.philips.com   |
|_______________________________________|
|  Standard disclaimer:  All opinions   |
|  expressed are  mine,  mine,  mine!!  |
|_______________________________________|
