[gnugo-devel] new to the engine and curious

[Martin Holters]

Hi,

I have recently become interested in GnuGo and when analysing some
toy-example (with a recent CVS version) to get some understanding of
what's going on (and possibly be able to do some tuning), I have gotten
the following:

> [...] --decide-string O9
> [...]
> O9 cannot be attacked (15 variations)

The O9 group is trivially alive with two rock-solid eyes.

> [...] --decide-connection K9/O9
> [...]
> K9 and O9 can be connected at M9 (18 variations)
> K9 and O9 can be disconnected at L8 (1 variations)

This analysis is correct.

> [...] --decide-string K9
> [...]
> K9 can be attacked at L8 (3 variations)
> K9 cannot be defended (9 variations)

Now, of course K9 could be defended by above connection, which GnuGo
doesn't consider. However, when used to determine the best move
globally, GnuGo finds this connection to be best (except for non-local
moves in empty corners). Could someone give me a short explanation as of
why GnuGo doesn't consider this connection when invoked with
--decide-string? Could this be changed by adding an appropriate pattern?
If so, where? I've tried adding very specific connection patterns to
patterns.db and patterns2.db (what's the difference, btw?), without
success.

I think the above is a somewhat fundamental weirdness, so just solving
it for this example maybe is not the best solution, but for the curious,
it's basically

XXXXXO
XO...O
XO.O.O
XXXXXO

where the right-most O-string is part of an alive group.

Thanks for any feed-back
Martin