Weston
On 10/22/06, Don Dailey <[EMAIL PROTECTED]> wrote:
I'm in a similar situation, I'm trying to identify classes of moves
that I can eliminate in an admissible way - which means the move I am
throwing out is either not the best move, or there are other equally
good moves.
I know that pass moves can be the best move in seki situations - and
it's non-trivial how to identify them.
I'm not good at go and this is a severe handicap for me, but here is
what I come up with so far - please add to my list if you know of
anything else:
1. Benson space - I use benson's algorithm to find pass-alive groups
and if a small "region" is enclosed completely by benson
groups, there is never a point moving inside of them for either
color (except in cleanup situations for Chinese rules)
A "region" is defined as strings of points that can consist of
any combination of enemy stones and empty intersections.
A large region can exist inside benson safe groups that allows
for life - so care must be taken that you identify the correct
regions. I don't know if I'm doing it the most efficient way,
but I'm going by region size. A region of 7 inside a benson
group cannot possibly support enemy life. So moves inside them
by either color do not improve the position.
2. I have a quick and dirty pass rule - I throw out all pass moves
in the early part of the game. I can't prove this rule is
admissible but I feel very safe with a rule like, "don't allow
pass if half the points on the board are empty."
I feel you can probably be a lot less conservative - but if anyone
knows a way to identify when to start including pass moves in a
search in a theoretically sound way - I'm all ears!
3. Unfortunately, the eye-filling rule is not admissible other than
in benson situations. The eye-filling rule I use has been
described on this group - don't move to a point surrounded on
all sides by stones of the same color - where the opponent
doesn't occupy more than 1 diagonal (different if on edge of
board.) I may or may not use this rule depending on what I'm
trying to do.
4. Don't move to any of the corner points on the first move.
Right not I'm working on a perfect solver for 5x5 - and rule 1 and 2 are
the only rules I know that are 100% admissible. I suspect rules 2 and
4 are admissible - at least on 5x5 or larger although I cannot back that
up with any theory.
Rule 4, the corner rule can probably be generalized - and I think that's
what a good pattern database might be able to do. I would like to be
able to build an admissible pattern database of the form that veto's
specific moves. But the database must be provably correct, not built
based on a humans intuition that a move is "probably" not good.
So I'm basically lost here. my solver is just a step towards the goal
of a pattern database that can admissibly remove many pointless moves
from a tree search.
- Don
On Sun, 2006-10-22 at 10:47 -0700, Phil G wrote:
> Does anyone have an example where "pass" is the best move, and not
> part of the two passes to end the game? I'm trying to determine if
> passes should ever be considered in a search for the best move, and if
> so, how to exclude them until it is really necessary.
>
>
>
> Thanks,
>
>
>
> Phil
>
>
>
>
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