GNU Go Documentation
12.9 The Connections Database
The patterns in `conn.db' are used for helping make_dragons()
amalgamate worms into dragons and to some extent for modifying eye spaces.
The patterns in this database use the classifications `B',
`C', and `e'. `B' patterns are used for finding cutting points,
where amalgamation should not be performed, `C' patterns are used for
finding existing connections, over which amalgamation is to be done, and
`e' patterns are used for modifying eye spaces and reevaluating lunches.
There are also some patterns without classification, which use action lines to
have an impact. These are matched together with the `C' patterns. Further
details and examples can be found in See section 10. Worms and Dragons.
We will illustrate these databases by example. In this situation:
`X' cannot play safely at the cutting point, so the `O' dragons
are to be amalgamated. Two patterns are matched here:
| | Pattern CC204
O
.
O
:+,C
O
A
O
;!safe_xmove(A) && !ko(A) && !xcut(A)
Pattern CC205
XO
O.
:\,C
AO
OB
;attack(A) || (!safe_xmove(B) && !ko(B) && !xcut(B))
|
The constraints are mostly clear. For example the second
pattern should not be matched if the `X' stone cannot
be attacked and `X' can play safely at `B', or
if `B' is a ko. The constraint !xcut(B) means
that connection has not previously been inhibited by
find_cuts. For example consider this situation:
The previous pattern is matched here twice, yet `X' can push
in and break one of the connections. To fix this, we include
a pattern:
| | Pattern CB11
?OX?
O!OX
?*!O
??O?
:8,B
?OA?
OaOB
?*bO
??O?
; !attack(A) && !attack(B) && !xplay_attack(*,a,b,*) && !xplay_attack(*,b,a,*)
|
After this pattern is found, the xcut autohelper macro will return
true at any of the points `*', `a' and `b'. Thus the
patterns CB204 and CB205 will not be matched, and the dragons will
not be amalgamated.
