Author: Brian Richardson
Date: 13:11:18 04/02/00
I have changed Tinker to update material values incrementally (instead of in the
eval function each time). This saved at most about 5%. I did this to enable
futility pruning (I think this is what it is called).
In the q-search, the net material is found from the perspective of the side on
move. Then, BEFORE doing the usual:
x=eval();
if(x>=beta) return(beta);
if(x>alpha)alpha=x;
FindCaptureMoves(); ...
I quickly check:
if ((x - 2*Pawn) >= beta) return(beta);
assuming 2 pawns is about largest positional score (LPS). And then
if ((x + 5*Pawn) <= alpha) return(alpha);
assuming that if winning a rook doesn't help more than alpha, just return.
Next, in the loop trying each capture move, before actually making the capture
move and calling x = -quiesce(-beta,-alpha), I see what the expected material
gain would be (taking into account promotions and enpassant). If that plus
3 pawns is <= alpha then skip actually doing this capture, and try the next one.
In this case, I assume the LPS is about 3 pawns. I know, it is not consistent,
but when i tried 2 pawns here, the search results would change, and I really
don't know what the LPS actually is.
Together these two "improvements" yield about 15% faster search times to a given
depth (in some cases >50%).
So, my question is does this all seem "reasonable". I know implementing a SEE
would probably be better, but I'm not up to that yet. I also tried some of
these cuts in the normal search routine, but that seemed to hurt things.
Thanks again for any feedback.
Brian
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