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Subject: Re: MVA/LVA sorting order

Author: Bruce Moreland

Date: 08:38:44 03/12/99

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On March 12, 1999 at 02:26:49, JW de Kort wrote:

>Hi chess friends,
>
>I have a small basic question about MVA/LVA move ordering. I have come across
>this methode a few time, but i'am not sure what it accectly means?
>
>Does it mean to sort captures:
>
>1. Acoording to the difference of the capturing piece and the captured piece
>
>or
>
>2. Sort all captures first using the piece value of the most valued captured
>piece and as a second critrium use the value of the capturing piece.
>
>e.g suposse we have the following possible captures: PxN, PxR, QxR
>
>using methode 1: PxR, PxN, QxR
>using methode 2: PxR, QxR, PxN
>
>Wich one is MVA/LVA?
>
>Thanks in advance
>
>Jan Willem

Piece    Index    Value
-------  -------  -------
Pawn     0        100
Knight   1        300
Bishop   2        300
Rook     3        500
Queen    4        900
King     5        10000

MVV/LVA sorts captures as follows:

Primary key:  Value of taken piece, descending order.
Secondary key:  Index of capturing piece, ascending order.

This can be easily implemented by using a single key, which is Value(defender) -
Index(attacker), although if you do this, you'd need to use centipawns or
millipawns as values (as most people do), you couldn't use whole pawn units,
since the value term needs to dominate the index term.

This will sort captures so that the biggest captured pieces come first, but if
two pieces can capture the same type of piece, you'll try the weaker capturer
first.

bruce



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