[gnugo-devel] failed 3,3 invasion defense

[Evan Berggren Daniel]

I watched in horror today as gnugo failed to defend against a very early
and slightly non-joseki 3,3 invasion.  I believe this patch to hoshi.sgf
is the easiest way to fix it.

There may be something better to do about it, but this seemed simplest,
and it clearly needs to not happen again.

This patch also corrects gnugo's preffered continuation on an empty board
to the hane at the 4,2 point (hanging connection at the other end).

I haven't found any other ways to trip up gnugo with an early 3,3.

The game in question is gnugo-3.3.10-niki-200210281349.sgf

Thanks

Evan Daniel

Index: patterns/hoshi.sgf
===================================================================
RCS file: /cvsroot/gnugo/gnugo/patterns/hoshi.sgf,v
retrieving revision 1.12
diff -u -r1.12 hoshi.sgf
--- patterns/hoshi.sgf  12 Jun 2002 15:35:06 -0000      1.12
+++ patterns/hoshi.sgf  28 Oct 2002 13:40:49 -0000
@@ -513,7 +492,8 @@

 (;W[rd]C[#Not joseki
 ]
-(;B[re]MA[nf]C[S];W[rc]MA[nf]C[S]
+(;B[re]MA[nf]C[U
+];W[rc]MA[nf]C[S]
 (;B[qf]C[j
 ]MA[ng];W[ob]MA[nf]C[S];B[nc]MA[mf]C[S];W[nb]MA[mf]C[S];
 B[mc]MA[lf]C[S])
@@ -522,10 +502,20 @@
 S
 ]
 MA[mg])
+
+(;B[ob]MA[lh]
+C[0
+#maybe possible, but gnugo screws it up with the following sequence
+]
+;W[od];B[qa];W[qe];B[pe];W[qf];B[rf];W[rg];B[qg];W[pf];B[pg];W[oe])
 )

 (;B[od]MA[nf]C[0
 ])
+
+(;B[nd]C[0
+#not joseki
+]MA[mf])
 )
 )