Re: [computer-go] Re: Re: Re: double threats

[David Fotland <fotland@xxxxxxxxxxxxxxx>]

I want to get one of 4 results from block tactical evaluation:

Tactically stable (live groups must have all blocks tactically stable)
Tactically captured (these are eyes and connection for opponent)
Tactically unsettled - captured or escapes depending on who moves first 
(good to know for miai situations for eyes or connections)
Tactically unclear - a ko, or double threat (needs some full board reading)

I find that the three searches I described give me this information.  I'd 
have to spend some time thinking
about the benefit of the 4th search.  There probably is one, but I don't 
know if it justifies the time spent.

Unfortunately, as computers get faster, and the program spends more time 
reading, more blocks end up in
the unclear category, forcing more full board reading.

Regards,

David

At 04:45 PM 1/10/2004 +0000, you wrote:
> Hello,
>
>
> Jens Lieberum wrote:
> >There remains the (maybe unlikely) case of an unsettled block where a search
> >with W to move first, B wins all kos and W must answer nearby threats would
> >return "dead". In this case the status should be "special unsettled" as
> >well. Does the additional time to determine this status exactly not
> >sufficiently pay off in playing strength?
>
>
>
> David Fotland wrote:
> >I assume that if a W group can be captured with W moving first, it will 
> also be
> >captured with B moving first.
>
>
>
> Sorry, I still did not get it and I hope that I do not write complete 
> nonsense now.
> I agree with your assumption that if W moves first and the block is dead, 
> then it will also be dead if B moves first (given the same ko winner and 
> the same defender of nearby threats). But still, after the three block 
> searches you do, the question remains open whether or not the block is 
> alive or dead under the conditions I mentioned (W moves first, B wins kos, 
> W must answer nearby threats). If it turns out to be dead, then the status 
> of the block depends on ko or nearby threats if W moves first and it is 
> dead if B moves first. This situation is possible, and it might be better 
> to treat it by global evaluations in a quiescence search. For example, 
> this case might be important, if W is behind and wants to initiate a fight 
> (or if B wants to turn down this option).
> The fourth block search would lead to four types of unsettled blocks, 
> three of them being special-unsettled (and each special case might require 
> a different treatment). The four types have a partial ordering. One type 
> is better for white, one better for black, and two uncomparable cases in 
> the middle. One of the middle cases is unsettled (not special), the other 
> middle case is the most unlikely one, but I guess that it is not 
> impossible (e.g. it might appear in situations involving a two-step-ko). 
> Of course, some good examples would be necessary to see, if it is really 
> helpful to distinguish all these cases.
> Anyway, these considerations are far too advanced for what I am trying to 
> do at the moment and I am very satisfied with the overview on possible 
> solutions I got now.
>
> Jens
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