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## Re: [gnugo-devel] eye patterns

 From: Arend Bayer Subject: Re: [gnugo-devel] eye patterns Date: Fri, 4 Apr 2003 11:01:28 -0500 (EST)

```
Gunnar wrote:

> Paul wrote:
> > - different kinds of marginal vertices supported by graph matcher
> >
> > see comments in eyes.db part of the patch for details.
>
> +# The patterns that look the same but differ in types of marginal
> +# vertices (see below) are sorted in the order "any", "neutral",
> +# "biased" from the first marginal vertex to the last.
> +#
> +# #######
> +#
> +# The semicolon lines that appear after some patterns specify the types
> +# of marginal vertices which can be matched against pattern's vertices.
> +# Allowed types are "any", "neutral" and "biased". Consider this artificial
> +# position:
> +#
> +#     XXX            Both white dragons have one eye each. However, the
> +#   OOOOOX.XOOOOO    eye to the right is safe as it stands, while the
> +#   OXXX!XX.!XXXO    one on the left needs defense immediatly. Both
> +#   OOOOOX.XOOOOO    vertices marked with '!' are marginal, but they
> +#     XXX            are clearly different. The left one is called
> +#                    "neutral" since it has alive neighbors of both
> +# colors. The right one is "biased" for it favors one of the players.
> +#
> +# "any" is of course a wildcard, it allows any marginal vertex to match
> +# against a given position in a pattern. It is the default type and when
> +# a pattern doesn't have a semicolon line, all it marginal vertices have
> +# "any" attribute set.

Wouldn't a safe_move() constraint be more useful? E.g. consider:

> +#     XXX
> +#   OOOOOX.XOOOOO
> +#   OXXX!XX.X!XXO
> +#   OOOOOX.XOOOOO
> +#     XXX
> +#

The marginal point on the right side might better be considered biased.
But as per Gunnar's examples, this treats just one more special case.

(...)

> For now we could maybe use the patch, but the question of added
> complexity in the eye database remains. Does anybody else have an
> opinion whether it pays off?

As the patch doesn't have a big immediate benefit, the main question
might be whether it makes further experiments/improvements with the eye
code more or less difficult. I guess that is for you and Paul to decide.

Arend

```