[Computer-go] Semeais

[David Fotland]

> -----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 10:12 AM
> To: computer-go at dvandva.org
> Subject: Re: [Computer-go] Semeais
> 
> On Fri, 14 Jan 2011, David Fotland wrote:
> 
> > 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.
> 
> As I understand it, the idea was that during the playout, if any move is
> made
> by the losing side within the semeai, it triggers an automatic answer to
> keep
> the semeai solved in the same way; and the winning side is forbidden to
> play in the semeai otherwise.
> (at least because of the semeai, a move chosen by proximity heuristics
> or patterns not from the semeai would be OK, I guess.)
> 
> > 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.
> 
> Sure.
> That was also why it was suggested just to bluntly finish the semeai
> before the playout, but maybe that bias is also too big.
> 
> Jonas

What do you mean by "finish the semeai".  Usually that means that neither
side should play here, since the position is settled.  Nevertheless there
are eyeless groups on the board, and by the end of the game one of the
groups will be removed.  The playouts have to deal with this.

David