Re: computer-go: Searches

[David Fotland <fotland@xxxxxxxxxxxxxxx>]

This is part of the evaluation function, not a move generator.  To
evaluate a position you must first know the tactical status of
each string of stones with a small number of liberties.

I use the same ladder reader to aid in evaluating conenctions
and eyes, when the connection or eye involves the tactical
status of hypothetical stones.

An 80 ply ladder doesn't have to bounce around.  It just crosses the
board once on a long diagonal (and a little extra).  Often there
are several ply of local moves before the ladder starts, since I read
groups with up to 4 liberties.

David

At 04:46 PM 12/5/99 +0000, you wrote:
>David Fotland wrote:
>> 
>> At 11:50 AM 11/20/99 +0100, you wrote:
>> >
>> >I can think of a few different ("local") look-ahead procedures that 
>> >should exist in most programs:
>> >  - ladder reader: read as deep as it takes, but not very wide (terminate
>> >    when the running group has three liberties.
>> 
>> Many Faces reads until the group gets 5 liberties, two eyes, seki, or
>> is captured for each string/block.  Each is read 3 times to distinguish
>> unconditional vs kos, and interactions with nearby friendly groups.  
>> Results are cached to avoid rereading.  Search is deep but not wide.
>> Up to 80 ply deep.  Beyond the first few ply, only 1 or 2 cantidate
>> moves are tried, so the move generator is quite complex.  Each seach is
>> limited to about 120 unforced nodes.  I use alpha-beta depth first search
>> with a small transposition table per search.
>> 
>Is this in order to determine connectivity of groups, or is it actually
>used to determine moves? I am thinking of the proverb "only amateurs
>play clever moves". Playing a move because it starts a ladder which
>bounces around the board and works when read to 80 ply would seem like
>a clever move. Of course, computers may not have much choice BUT to make
>clever moves. 
>
>Best wishes,
>
>Julian
>
>--
>Julian Richardson                         http://www.dai.ed.ac.uk/~julianr/
>Mathematical Reasoning Group, Edinburgh University, Phone: +44 131 650 2720 
>
>