Author: Andreas Guettinger
Date: 10:33:46 09/21/02
Go up one level in this thread
On September 21, 2002 at 12:20:24, scott farrell wrote:
While i looked at you code, i had th impression that you implemented MMV/LVA not
correctly. You do a pieceValue[victim] - pieceValue[attacker] for determining
your mvvlva value. Instead for mvvvlva do something like this:
value = pieceValue[victim] - attacker;
where pieceValue for example is:
queen = 900
rook = 400
bishop, night = 300
pawn = 100
(or the values you use)
but for attacker take:
pawn = 1;
knight = 2;
bishop = 3;
rook = 4;
queen = 5;
In this case, the value of a pawn capturing a queen is 900-1 = 899 an will be
prefered over a knight capturing a queen 900-2 = 898. This should improve your
sorting.
regards
Andy
>I was just fiddling with my move ordering (as we all do from time to time).
>
>I found that my MVVLVA code worsened (is that a word?) my move ordering, and
>slow my searches significantly.
>
>I altered it to just simply ordering the capture by the size of the material it
>is to take, disregarding the size of the piece to perform the capture.
>
>As far as I know current wisdom for move ordering is something like this:
>1. from hastable first
>2. killers next
>3. winning captures ordered by MVVLVA
>4. other moves
>5. losing captures
>
>My updated move ordering is:
>1. from hastable first
>2. killers next
>3. all captures, ordered by the size of the captured piece (largest first), and
>ties broken by size of attacker only
>4. other moves
>5. losing captures
>
>I havent looked into to hard just yet, but I am pretty sure its got something to
>do with search extensions, and recapture extensions. Running all the captures
>first allows the extensions to kick in quickly and cause lots of nice cutoffs.
>
>The other thing it might be is a bug in my code - and turning off the MVVLVA
>ordering of capture bypassed the bug, but its only a few lines, and I dont think
>there is any bugs.
>
>What do you all think? am I crazy, do I have a bug, or are some programs already
>doing this?
>
>Scott
>
>Here is my old code:
>
> if (moves[depthTree][i].capture > 0)
> {
> //black is capturing a white piece
> if (b.isAttacked(moves[depthTree][i].s2, Board.WHITE))
> moves[depthTree][i].searchOrder
> += (Board.pieceValues[moves[depthTree][i].capture]
> - Board.pieceValues[
> - moves[depthTree][i].piece])
> * 100000 ;
> else
> //enpris
> moves[depthTree][i].searchOrder
> += Board.pieceValues[moves[depthTree][i].capture]
> * 100000 ;
> } else if (moves[depthTree][i].capture < 0)
> {
> //white is capturing a black
> if (b.isAttacked(moves[depthTree][i].s2, Board.BLACK))
> moves[depthTree][i].searchOrder
> += (Board.pieceValues[-moves[depthTree][i].capture]
> - Board.pieceValues[moves[depthTree][i].piece])
> * 100000 ;
> else
> //enpris
> moves[depthTree][i].searchOrder
> += Board.pieceValues[-moves[depthTree][i].capture]
> * 100000 ;
> }
>
>
>and my new code that is much much better at ordering:
>
> if (moves[depthTree][i].capture > 0)
> {
> moves[depthTree][i].searchOrder
> += (Board.pieceValues[moves[depthTree][i].capture] +
>moves[depthTree][i].piece)
> * 1000;
> } else
> {
> moves[depthTree][i].searchOrder
> += (Board.pieceValues[-moves[depthTree][i].capture] -
>moves[depthTree][i].piece)
> * 1000;
> }
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