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Subject: Re: To Bob: Crafty, move ordering with SEE

Author: Bruce Moreland

Date: 23:58:47 09/06/99

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On September 07, 1999 at 02:41:02, Alessandro Damiani wrote:

>Hi Bob!
>
>Some time back you wrote here on CCC about the move ordering of Crafty. I don't
>want to download all archive files, so I ask you now.
>
>If I remember it right, you use a SEE to order captures in the search. The
>negative captures (SwapOff(.)<0) are placed after ALL the other moves?
>
>I thought, the "state of the art" is:
>
>1. transposition table move
>2. positive captures (MVV/LVA)
>3. killer 1
>4. killer 2
>5. counter move
>6. rest of captures (MVV/LVA)
>7. history moves
>8. rest of moves (static ordering)
>
>I define "positive capture" this way:
>Val(aggressor)<Val(victim) OR NOT Attacked(opponent, move.to).
>
>You said that the SEE gives you a better move ordering when the negative
>captures are put after number 8?
>
>Thank you!
>
>Alessandro (new E-mail address since today: adamiani@econophone.ch)

I am not Bob, but I have found independently that it does.  It is worth trying
both ways.

This orders "sacrifices" behind non-capturing moves, but most losing captures
are crap.  If you no winning captures in a position, one losing capture, and a
bunch of random moves that do nothing, you probably have a better chance at a
cutoff if you do one of the other moves.  Also, if you start capturing, you tend
to capture again at the next ply, which means you do more nodes.

Speculation on my part.

bruce




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