[gnugo-devel] evan_5_1.2

[Arend Bayer]

This patch adds, starting with,

+--------+
+........|
+........|
+.....*..|
+....X...|
+........|
+.....O..|
+........|
+........|
+
+:8,sFJ

the following variation (plus some followups):

O to move first:
+--------+
+........|
+........|
+..9.317.|
+...4X25.|
+.....86.|
+....aO..|
+........|
+........|

(X 10 on a).


I have two remarks about this:

1.) The move at * wouldn't have occurred to me. Then I checked with
kombilo (I really recommend installing kombilo to everyone interested
in joseki study -- whether for gnugo or for your own games), and I indeed
did find it in a lot of pro games. But they were all in the following
situation (or similar):

-------------+
.............|
.............|
..aX......*..|
...,.....X...|
.............|
..........O..|
.............|
.............|

In all the games, X had a stone at the hoshi on the left side, or as
in  the diagram, or at "a". What is the reason behind this?
Usually, the variation in the diagram above (without a pincer) is bad for
white. But when it's played in the situation as in the last diagram,
the black stone on the top ends up badly placed, thus leading to
a fair result overall.

2. Now if black does have a stone at the top, than its usually better
(and probably even more so for gnugo) to block on the other side
(i.e. B2 at 3 in the variation above.)

So I think the joseki needs a little more context. Maybe we should merge
the patch as it is, however, without marking W1 above as joseki.

Arend