[Computer-go] Semeais

[David Fotland]

The static evaluation gets the correct status for the groups in the semeai.  The static evaluation thinks that white is far, far ahead.  The MCTS engine thinks black wins 60%, so the playouts don’t get it right.

It's a little frustrating that MCTS is so much stronger, even though in many simple positions it is far weaker than the static evaluation.

David

> -----Original Message-----
> From: computer-go-bounces at dvandva.org [mailto:computer-go-
> bounces at dvandva.org] On Behalf Of Aja
> Sent: Friday, January 14, 2011 10:06 AM
> To: computer-go at dvandva.org
> Subject: Re: [Computer-go] Semeais
> 
> David, can Many Faces solve this position posted by Magnus?
> 
> http://www.littlegolem.net/jsp/game/game.jsp?gid=1226980
> 
> I test this position in Erica, Erica can score/solve it correctly. But
> that
> is because I tried to handle similar positions in the past. Erica still
> fails easily if the condition is different. We really need a general
> soluation for semeai, so that we don't need to deal with so many cases of
> semeai.
> 
> Aja
> 
> 
> -----????-----
> From: David Fotland
> Sent: Saturday, January 15, 2011 1:58 AM
> To: computer-go at dvandva.org
> Subject: Re: [Computer-go] Semeais
> 
> Many Faces does something like this, and it does not work well.  Many
> Faces
> includes a static semeai solver with local search, and this is applied in
> the tree.  If anyone has many faces you can set up a semeai and ask for
> group status.  This shows you the result of the static life/death/strength
> analysis, and you can see the kind of semeai it will leave for the
> playouts.
> 
> The problem comes when the tree finds the semeai, and the correct move is
> made in the tree to resolve the semeai.  At the exit from the tree, any
> semeai on the board has been resolved (in that one side will win by
> typically one move).  The tree won't waste extra moves in the semeai, so
> at
> tree exit, the winning side is one move ahead.
> 
> Then the playout has no clue about the semeai, and lets the losing side
> win
> perhaps 40% of the time.
> 
> Semeai knowledge is required in the playout.  The tree must leave resolved
> semeai positions on the board which the playouts can't understand,
> introducing a large bias.
> 
> David
> 
> > -----Original Message-----
> > From: computer-go-bounces at dvandva.org [mailto:computer-go-
> > bounces at dvandva.org] On Behalf Of Kahn Jonas
> > Sent: Friday, January 14, 2011 9:35 AM
> > To: computer-go at dvandva.org
> > Subject: Re: [Computer-go] Semeais
> >
> > On Fri, 14 Jan 2011, terry mcintyre wrote:
> >
> > > It is expensive to solve semeai during every playout, but what if
> semeai
> > > solutions were done once per game move (or even less frequently), and
> > the
> > > information obtained were then amortized over many playouts?
> > >
> > > The top-level analysis would solve the semeai, and create a self-
> > updating
> > > set of move-response triggers. The tricky bit is that the indicated
> > > behavior must correctly adapt to all possible moves during a complete
> > > playout, in a manner which does not interfere with other simultaneous
> > > playouts.
> >
> > I think that was the most common idea. At least that's how I understand
> > Olivier's ideas, and my vague suggestion also fits that description.
> >
> > I am copying the suggestion back here to add a remark.
> > >> We may make a local tree (moves only in the zone or that take away a
> > >> liberty of one of the groups), first without tenukis, and see who
> wins.
> > >> We may then add tenukis for the winning side.
> >
> > (Tenukis mean pass move since it's a local tree.)
> >
> > >> During playouts, (we may use that during playouts rather than at the
> > >> beginning), when a move is played in the area, the winning side has
> to
> > >> follow the tree along a winning line.
> >
> > In fact, we also need to make the tree for when the other side is
> > winning: taking ko into account during playouts is out-of-reach today,
> > but by the time we leave the MCTS tree to enter the playout, there may
> > have been a move added for free in the local area (ko in the tree). And
> > then the other side is the winner for this playout.
> >
> > Jonas
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