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Re[4]: [gnugo-devel] life & death (3.3.5)

From: Paul Pogonyshev
Subject: Re[4]: [gnugo-devel] life & death (3.3.5)
Date: Thu, 29 Aug 2002 00:39:55 +0300

Gunnar wrote:
>>    - check if they are connectable with moves outside eye shape (A8 and
>>      C7 can be connected by C8, A4 and C7 cannot be connected).

> This is not trivial, in the sense that we don't have a machinery in
> place for this analysis.

there's some code that analyzes probability of a dragon to escape (to
connect to another stones). can't we use a modification here?

>>    - separate the dragon into parts which must be connected (in case
>>      of attack) with moves inside eye shape (2 parts A8+C7 and A4).

> This is not clear. If black attacks at C8, doesn't white have to
> connect A8 and C7 inside the eye space as well?

yes, this can be probably analyzed the same way (if it ever works,
that's it ;)

>>    - enumerate common liberties/connections of different parts (here
>>      goes the vague part) - parts can be "connected" by A5 or B5.

> Indeed, this is quite vague.

maybe it is better to say: since A4 string has only two liberties
inside eye shape, black A5 forces B5 (maybe later, but B5 becomes a

>>    - note that black A5 forces us to play B5 sooner or later (black
>>      can just make atari).

> This is kind of a key point, but how do we carry out the analysis
> leading to the conclusion?

if we can find somehow that there's no way to connect A4 string to
anything else (or to other strings of the same dragon outside the eye
shape) and we see that it has the only liberty remaining in the eye
shape, we can conclude that the liberty is to be filled to connect A4
with the rest of the dragon.

>> [...]

>> well, this is an intricate explanation, but i think i managed to
>> formulate the main idea. maybe it would allow to impove life & death
>> code somewhat.

> It's a good start, even though it probably needs a lot of refinement.
> In any case this is an important problem to solve.

just an idea, it should be worked on a lot before coding can be
started, that's for sure.

Paul Pogonyshev

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