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Subject: Unsuccessful experiments in move ordering

Author: Scott Gasch

Date: 17:45:14 12/13/00


Hi,

I had an idea recently about improving the ordering of non-captures.  Up until
now I have been using a history heuristic (with 2 killers).

The idea is to try non-captures that threaton the last piece moved, flee from
the last moved piece, or whose "footprint" overlaps the footprint of the last
move before their peers.  By footprint I mean the set of squares a piece of type
T in square X can move to if nothing else is on the board.

Doing some tests on different positions I decided to throw away the "flees"
case...  I am skeptical of its soundness and it always grew the tree...
sometimes quite severly.

The other two (overlapping footprints and attacks the last moved piece) both
grow the tree anywhere from slightly to greatly.  I tried different bonus
weights, bonus + history and bonus alone, etc... and the best I ever got was
trees of equal size in _some_ positions.

Despite this fact I still think there might be some merit in this idea.  Surely
its better for move ordering to try, for example, threatoning pawn pushes before
quiet ones or moving a to support a square attacked by the opponent's last move
before moving randomly... My question to you guys is if anyone else is doing
anything similar and what have your results been like?

Thanks,
Scott



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