Re: [gnugo-devel] gnugo 3.4 problems

[bump]

> > W gets the ko by answering C19 with W:A14. And it isn't
> > a very good ko. W has to win it multiple times and if B
> > can't fight it, he can lose it about twice (taking
> > profit elsewhere) then chicken out and the worst that
> > can happen to him is seki. So W is fighting a very
> > uphill ko for seki. So the test should be written:
> 
> What variations are you considering? I see one where white has to
> ignore multiple ko threats to win the semeai but where black has no
> option to chicken out (white might settle with seki at some point
> though). In another variation I find black can chicken out for seki
> but then white only needs to ignore one ko threat.

Here's some variations. For B, ``chickening out'' means
playing at E19, which he has the option of doing even
after W wins the ko once or twice. After that, seki is the
most probable outcome, since W can still try to kill, but at a
price of (I think) ignoring two B tenukis, plus losing sente.
The incentive to take the sente will be too strong for W to
ignore.

If W has enough ko threats, I think seki is the most
likely outcome. However W must come up with the first
ko threat, so this is KO_B for W.

I think it is a good idea to think about this example
and to ask how it SHOULD be analyzed.

> > Maybe not, because the need for an elaborate
> > classification is strongest in the case of semeai.
> > The KO_A/KO_B scheme seems be adequate for ordinary
> > owl reading, where there is only one group in
> > question.
> 
> In my opinion we should change in all kinds of reading if we change.

I think that indirect kos are quite common in semeai situations
but less so where only one group is at stake, though there is
the complication that there could be internal ko threats. If
there is only one group, usually one fights a ko to gain an
eye. Such a ko is direct since whoever wins it can immediately
settle the issue. But if there are two groups, there is
another way kos can happen (like in this game) where one
fights a ko to keep a liberty open while one tries to fill the
opponent's liberties. These ``yose kos'' seem special to
semeai.

Do you have some examples that are not semeai where
the KO_A, KO_B scheme is inadequate?

Note: I may not have e-mail tomorrow.

Dan

(;GM[1]FF[3]
SZ[19]
GN[GNU Go 3.5.10 load and print]
DT[2004-11-20]
KM[0]RU[Japanese]AP[GNU Go:3.5.10]PL[B]
AW[ha][ab][bb][ib][mb][pb][qb][cc][ec][fc][gc][hc][ic][oc][pc][ad][cd][fd][jd][ld][be][ce][de][ee][cf][qf][mg][ph][qq][pr][rr]
AB[ba][cb][db][eb][fb][gb][hb][kb][rb][bc][dc][qc][dd][ed][gd][nd][od][pd][qd][fe][bf][ef][ff][bg][cg][jh][dj][jj][pj][pm][dp][jp][pp][qp][rp][mq][rq]
;B[ca];W[af];B[ag];W[ga];B[df];W[fa];B[ae];W[tt]
C[W makes a ko threat
];B[tt]C[B answers
];W[af]
(;B[ea]
C[This move is ``chickening out.'' The most probable outcome is seki.
It is possible for W to try to kill B but at a very high cost.
]
;W[ia];B[ae]C[
];W[tt]C[W makes a ko threat
];B[tt]C[B answers
];W[af]
C[
];B[tt]C[B tenuki.
]
(;W[ac]
C[W can try to kill B but this is unlikely to be a wise course.
];
B[ae]
(;W[bd];B[af]C[Seki.
B has one extra move outside but ends in gote.
])

(;W[tt]
C[W ko threat. If W wants to kill B he must fight ko one more time.
];
B[tt]C[B answers ko threat.
];W[af]C[Now it is a direct ko.
];B[tt]
C[B tenuki.
];W[aa]
C[W wins.
B has two extra moves outside, plus sente.
W had to make the first ko threat.
])
)

(;W[ae]
C[W can get seki, having won the ko twice and ignored one B tenuki. Or ...
B has one extra move outside, plus sente. W had to make the first ko threat.
])
)

(;B[tt]C[B tenuki.
];W[tt]C[W treats B's tenuki as a ko threat.
];
B[ae]C[
];W[tt]C[W ko threat.
];B[tt]C[B answers W's ko threat.
];
W[af]C[B tenuki.
];B[tt]
C[W can treat B's tenuki as a ko threat but eventually he must ignore B's
tenuki.
]
(;W[ea]C[This way there can be no seki
];B[ae];W[tt]C[Ko threat
];
B[tt]C[Answers ko threat
];W[af]C[
];B[tt];W[ac]
C[W wins.
B has two extra moves in the rest of the board plus sente.
W had to make the first ko threat.
])

(;W[ac]C[

];B[ae];W[bd]
(;B[aa];W[af];B[ia]C[One internal ko threat
];W[ja];B[ae];W[tt];B[bc]
C[B got an extra tenuki and still killed. W got sente.
])

(;B[ea]C[B has a sure sente if he wants it.
];W[ia];B[af]
C[Equal numbers of outside moves, W gets sente.
])
)
)

)