[Computer-go] living by two false eyes

valkyria at phmp.se valkyria at phmp.se
Wed Apr 6 09:32:47 PDT 2011


Valkyria prunes a lot of move and do a lot of computations for doing  
so. It also is faster with the code than without since games become  
shorter when stupid moves that kills groups are removed. If a large  
group is killed by light playouts on 19x19 then a light playout will  
play a lot of moves inside this area. In the worst case leading to  
even more cases...

With proper pruning and good patterns for defense playout get more  
civilized and shorter.

Valkyria also can call a function IsAlive(pos) that can tell if the  
stones near position "pos" have unconditional eyeshape. It does not  
handle all cases but some of them. Since it is only called when needed  
deep after many conditions have been fulfilled (for special patterns  
where life is likely and is important for if a move is relevant or  
not). I think it is more effective than running a fullboard eval of  
life and death after each move.

-Magnus



Quoting fastgo <fastgo at gmail.com>:

> if the region is marked as unconditionally belonging to either black or
> white, then black and white are forbidden to play inside the region.
>
> In the case we discussed, if both false eyes are identified as unconditional
> eye, then it cannot be filled. So no side will play inside in it.
>
> If a program has less blunder to fill eye, that definitely reduce the
> playout length.
>
> On Wed, Apr 6, 2011 at 12:05 PM, Brian Sheppard <sheppardco at aol.com> wrote:
>
>> How does the Benson algorithm result in shorter playouts?
>>
>> A more precise question: how does your playout apply the ability to
>> determine unconditional life to the question of which moves one should play
>> in the playout, or to determining whether to continue to play out.
>>
>> Thanks
>>
>> -----Original Message-----
>> From: computer-go-bounces at dvandva.org
>> [mailto:computer-go-bounces at dvandva.org] On Behalf Of Erik van der Werf
>> Sent: Wednesday, April 06, 2011 10:49 AM
>> To: computer-go at dvandva.org
>> Subject: Re: [Computer-go] living by two false eyes
>>
>> On Wed, Apr 6, 2011 at 4:11 PM, fastgo <fastgo at gmail.com> wrote:
>> > In StoneGrid, it has built in the Benson algorithm in the playout. It
>> does
>> > not seem to help much on overall strength. But I think it should solve
>> the
>> > case here.
>> >
>> > I think you can implement the Benson Algorithm in the late stage of the
>> > playout.
>> >
>> > It has another advantage finishing the playout in shorter length. In
>> > StoneGrid, the playout on average finishes in a little bit more than 70
>> > stones on 9x9.
>> >
>> > You need quite a lot of effort to get it fast as well as correct. So the
>> > return of the effort is low.
>>
>> I also have it in my program. The funny thing is that if I disable it
>> the program actually becomes slower because of the longer playouts...
>>
>> Erik
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