Author: Michael Henderson
Date: 12:38:30 08/20/04
Go up one level in this thread
On August 19, 2004 at 16:08:01, Eric Oldre wrote:
>a few nights ago i tried a idea i had for ordering quiet (non-capture) moves.
>
>here is my original ordering scheme:
>
>1) hash move
>2) winning captures (SEE > -.2: ordered by SEE)
>3) killer moves (non-captures)
>4) rest of moves, by SEE value.
>
>what i tried adding was:
>1) hash move
>2) winning captures (SEE > -.2: ordered by SEE)
>3) killer moves (non-captures)
>4) quiet moves that attack the space left behind by opponents last move (and
>don't have a bad SEE score)
>5) rest of moves, by SEE value.
>
>the code for number 4 looked something like this.
>
>//once per ply.
>chessmove lastmove = board->hist[board->moves_made_since_init-1].move_made;
>chesspiece lastpiece = MovePiece(lastmove);
>chessposition lastmovefrom = MoveFrom(lastmove);
>chessposition lastmoveto = MoveTo(lastmove);
>U64 lastmoveattacks = AttacksFromPiece(board,lastmoveto,lastpiece);
>U64 lastmoveleaves = AttacksFromPiece(board,lastmovefrom,lastpiece) &
>~lastmoveattacks;
>
>//for each non-capture that doesn't have a SEE < -.4
>U64 newattacks = AttacksFromPiece(board,moveto,movepiece);
>if(newattacks&lastmoveleaves){
> //meets criteria for search after killers
>}
>
>using this technique gave me about a 4% reduction in my tree size,
>when searching to a set depth in the first 50 positions of ECM.
>
>of course there was an overhead in the calculations, which happened to
>slow the program down just enough to make the time-to-depth measurement
>pretty much the same. less than .3% difference.
>
>for now I am going to take it out of my program and concentrate on other, bigger
>picture items.
>but I may come back to it someday...
>
>I also suspect that running the tests on a less tactical set of positions may
>improve
>the performace difference also.. any thoughts?
>
>Eric
>
>PS... for those that may have thought where i got this idea from, it was from
>watching the josh watzkin annotated games in CM9000. he seems to mention
>attacking the "space left behind" by the opponent a lot in his commentary.
I think you will get better returns at greater search depths and if you do not
use the quiet move ordering at the last ply in search.
Michael
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