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Subject: Re: Do you want to catch chess programs that cooks test suites ?

Author: Bruce Moreland

Date: 23:18:13 02/09/00

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On February 09, 2000 at 10:52:20, Andreas Stabel wrote:

>I hope somebody finds this useful

You don't explain how to use it or what conclusions to draw from any results.

It is possible that programs that do not cook test suites could produce
different results due to perfectly harmless effects.

1) l/r symmetry.  If you exchange left and right sides of the board, you can
create differences and play, because programs may handle k-side and q-side
castled positions differently, and may regard the position of the f-pawn
differently than they regard the position of the c-pawn.

2) b/w symmetry.  Changing colors could result in changes because it is possible
that a program has been tuned to play black differently than it plays white.

3) move generation order problems.  A typical chess program strategy is to
create a piece list, and generate moves in piece-list order.  The piece list has
to be constructed somehow, and the initial position of the pieces on the board
probably has something to do with this.  Also, once you get your piece list
generated, the moves have to be generated in some order, and the order may not
be the same if you reflect or rotate the board.  Meaning that a white knight on
e4 might try to move to c5 first, then d6, then f6, etc., whereas a black knight
on e5 might try to move to c6, then d7, then f7.  This will result in changes in
move generation order.  Changes in the order in which moves are generated can
result in changes in the order in which they are searched, which in turn can
cause all sorts of problems, such as forward pruning failures, history table and
killer move changes, etc.

So be careful with the conclusions you draw.

bruce



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