Re: [gnugo-devel] Tripod group

[bump]

> Yes, the tripod group is alive. :-)
> 
> See ld_owl:191-193 for the continuation. One variation ends in life in
> double ko.

The solution B18 given by Allan and Arend is convincing. There's
no double ko.

GNU Go prefers B19 which leads to variations looking like
the bottom right corner in tripod8.sgf. I assume the
double ko you are referring to is in this position.

+--------
|O.O..... 
|.OXX.... 
|OXXOOOOO
|.*OO.... 
|..O..... 
|..O..... 
|..O..... 

There's an actual error in GNU Go's reading, below
the owl branch depth. Here's an edited variation
tree. Note that GNU thinks the move is to the left of
*, which actually produces ko. This is at some depth
in the move tree. In the actual position GNU makes
the right move at *, but we can't say it read it out
correctly from the outset.

I think B18 is a much cleaner answer and we should tune
GNU Go to play that way.

Dan

(;GM[1]FF[3]
SZ[19]KM[0];
C[owl_attack B17: WIN C18 (attack effective)
  (24 variations)
owl_defend B17: WIN B19 (defense effective)
  (186 variations)]
AW[ca][dc][ec][fc][gc][mc][nc][oc][pc][cd][dd][pd][qd][ce][qe][re][cf][qf][cg][qg][cm][qm][cn][qn][bo][co][qo][cp][dp][pp][qp][dq][eq][fq][gq][mq][nq][oq][pq][br][or]
AB[db][qb][bc][cc][qc][rd][bp][aq][cq][qq][rq][cr][pr][qs];B[ba]
C[eat lunch at B17 (variation 1, hash ec2bdedb)
owl_attack B17: 0 (attack failed)
  (185 variations)
(next variation: 186)]
;W[bb]
C[A1319c at B17 (variation 43, hash c5ab613c)
owl_defend B17: WIN A18 (defense effective)
  (88 variations)
(next variation: 131)]
;B[ab]
C[eat lunch at B17 (variation 91, hash 3fbf5edf)
owl_attack B17: 0 (attack failed)
  (40 variations)
(next variation: 131)]
;W[aa]
C[A1206 at B17 (variation 94, hash 90da5c93)
owl_defend B17: WIN C18 (defense effective)
  (37 variations)
(next variation: 131)]
;B[cb]
C[eat lunch at B17 (variation 118, hash 36527eee)
owl_attack B17: 0 (attack failed)
  (13 variations)
(next variation: 131)]
;W[ac]
C[A1331 at C18 (variation 121, hash eb772b9)
owl_defend C18: WIN A16 (defense effective)
  (10 variations)
(next variation: 131)]
;B[ad]
C[eat lunch at C18 (variation 123, hash b9efb37a)
owl_attack C18: 0 (attack failed)
  (8 variations)
(next variation: 131)]
;W[bd]
C[A504 at C18 (variation 124, hash e2b29cc0)
owl_defend C18: WIN D19 (defense effective)
  (7 variations)
(next variation: 131)]
;B[da]
C[eat lunch at C18 (variation 125, hash a65d2265)
owl_attack C18: 0 (attack failed)
  (6 variations)
(next variation: 131)]
;W[eb]
C[A1501 at C18 (variation 126, hash 8f5f8d16)
owl_defend C18: WIN B19 (defense effective)
  (5 variations)
(next variation: 131)]
;B[ba]
C[eat lunch at C18 (variation 127, hash 61d8f9f3)
owl_attack C18: 0 (attack failed)
  (4 variations)
(next variation: 131)]
;W[tt]C[tenuki (ko threat)];B[tt]C[tenuki (answers ko threat)];W[ca]
C[tryko: VA13 (variation 128, 22c0990d)
owl_defend C18: WIN A18 (defense effective)
  (3 variations)
(next variation: 131)]
;B[ab]
C[eat lunch at C18 (variation 129, hash d146fb0b, komaster white:B19)
owl_defend C18: WIN B19 (defense effective)
  (2 variations)
find_defense B18: 0 (cached)
find_defense A19: 0 (cached)
find_defense C19: 0 (cached)
owl_attack C18: 0 (attack failed)
  (2 variations)
(next variation: 131)]
;B[ba]
C[VA44 at C18 (variation 130, hash 5126f165, komaster white border:B19)
owl_attack C18: 0 (2 or more secure eyes)
(next variation: 131)]
)