Problem Nr. 344 from Cho's intermediate Problems

[Marcus]

@Herman: Interesting. Now I need to figure out what I missed.

[tetron]

Always trying to refute the expert solution I thought I found the refutation.

$$c
$$ +-----------------------
$$ | . . . . 6 . 1 5 . . .
$$ | . O 2 O X X . . 3 4 .
$$ | 8 X 7 X X O X X O . .
$$ | . O X X O O . . O , .
$$ | . O O O . . . a . . .
$$ | . . . . . . . . . . .

Click Here To Show Diagram Code

[go]$$c
$$ +-----------------------
$$ | . . . . 6 . 1 5 . . .
$$ | . O 2 O X X . . 3 4 .
$$ | 8 X 7 X X O X X O . .
$$ | . O X X O O . . O , .
$$ | . O O O . . . a . . .
$$ | . . . . . . . . . . .[/go]

But, of course, it fails. W's containment is too weak. B easily walks out at a. The problem depends on W being weak around there. Correct?

This is an ancient problem. In ancient problems escape was a factor. Modern compositions tend to be self contained. Different conventions, I suppose, the ancient convention being that the unshown part of the board is empty, the modern convention being that the unshown part of the board is unknown.

I was relieved when someone suggested the shown 2 as my first instinct was that black still didn't have two eyes.

Assuming the rest of the board is unknown the white stones still haven't got two eyes either... I had been expecting a cleaner solution but I think that it is a more solution than you often see in modern problems.

I haven't played go for a very long time (if you don't count a computer program that was described on one website as the strongest free program but so many weaknesses didn't have a live stone.) and I am not sure that I would have expected the line to run to 'a'.

[jts]

I leave continuations and alternate variations to the viewer.

[Marcus]

I leave continuations and alternate variations to the viewer.

It's just my way of saying "I'm too lazy to figure out why this doesn't work", but I liked the variations I spotted, and couldn't immediately see a refutation. Silly me, I should have known there would be one ... I still haven't taken the time to look at it yet ... and, I just found it, I think, while typing this:

$$W White to kill
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . W . . . . . . . . .
$$ | . . O O O O O O . , .
$$ | O O X X . X X O . . .
$$ | X X 3 X 2 . X O . W .
$$ | X X 5 1 4 . . X . . .
$$ ----------------------

Click Here To Show Diagram Code

[go]$$W White to kill
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . W . . . . . . . . .
$$ | . . O O O O O O . , .
$$ | O O X X . X X O . . .
$$ | X X 3 X 2 . X O . W .
$$ | X X 5 1 4 . . X . . .
$$ ----------------------[/go]

Under the stones again for the win!

$$W White to kill
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . W . . . . . . . . .
$$ | . . O O O O O O . , .
$$ | O O X X . X X O . . .
$$ | X X . X 2 . X O . W .
$$ | X X a 1 4 3 b X . . .
$$ ----------------------

Click Here To Show Diagram Code

[go]$$W White to kill
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . W . . . . . . . . .
$$ | . . O O O O O O . , .
$$ | O O X X . X X O . . .
$$ | X X . X 2 . X O . W .
$$ | X X a 1 4 3 b X . . .
$$ ----------------------[/go]

a and b are miai for Black to live, if White plays a, Black can play b and count on that under the stones thing again for the 2nd eye.

[cyclops]

$$W White to kill
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . W . . . . . . . . .
$$ | . . O O O O O O . , .
$$ | O O X X . X X O . . .
$$ | X X . X . . X O . W .
$$ | X X . . . . . X . . .
$$ ----------------------

Click Here To Show Diagram Code

[go]$$W White to kill
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . W . . . . . . . . .
$$ | . . O O O O O O . , .
$$ | O O X X . X X O . . .
$$ | X X . X . . X O . W .
$$ | X X . . . . . X . . .
$$ ----------------------[/go]

@jts: That's not a modern problem! ......

http://senseis.xmp.net/?XuanxuanQijingProblem35

here a sgf of the ancient solution from Herman's link:

(;GM[1]FF[4]SZ[19]GN[]PC[http://lifein19x19.com/]AP[GoWiki:2009]DT[2011-11-01]C[Diagram from http://lifein19x19.com/

]PL[W]AB[cq][dq][fq][gq][ar][br][dr][gr][as][bs][hs]AW[bo][cp][dp][ep][fp][gp][hp][aq][bq][hq][hr][jr]CR[bo][jr];W[fs];B[eq];W[es];B[gs];W[ds];B[er];W[cr];B[cs];W[cr];B[br]
;W[bs];B[cs];W[ar];B[as];W[ir];B[fr];W[bs];B[is];W[cr];B[js]
;W[kr];B[br];W[es];B[as];W[ds];B[fs];W[bs];B[ks];W[lr];B[as]
;W[ds];B[es];W[bs];B[ls];W[cr];B[mr];W[ds];B[ms]
(;W[mq];B[nr];W[oq];B[or];W[pq];B[pr];W[qq];B[qr];W[rr];B[qs]
;W[os];B[nq];W[np];B[op];W[mp];B[rq];W[rp];B[sq];W[sr];B[qp]
;W[sp];B[rq];W[sq];B[pp];W[rq];B[qn];W[rn];B[rm];W[qo];B[po]
;W[pn];B[ro];W[oo];B[qo];W[qm];B[sn];W[so];B[rn];W[rl];B[sm]
;W[sl])
(;W[nq]C[this move also seems to work]))

[Chew Terr]

...I'll tell you, that's not the solution I expected.

[Marcus]

...I'll tell you, that's not the solution I expected.

I know! Actually, it's a great problem for studying how many different ways black can live, if White deviates almost anywhere.

[entropi]

...I'll tell you, that's not the solution I expected.

Indeed, such an innocent looking position being the (one of the) most difficult problem(s) ever. I wonder what comes next!!!

[HermanHiddema]

...I'll tell you, that's not the solution I expected.

Indeed, such an innocent looking position being the (one of the) most difficult problem(s) ever. I wonder what comes next!!!

Well, if we're posting innocent looking positions....

$$W White to play
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . O O . O O . . .
$$ | . . . . . . O . .
$$ | . X X . . . . O .
$$ | . . . . . X . O .
$$ | . . . . . . . . .
$$ +------------------

Click Here To Show Diagram Code

[go]$$W White to play
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . O O . O O . . .
$$ | . . . . . . O . .
$$ | . X X . . . . O .
$$ | . . . . . X . O .
$$ | . . . . . . . . .
$$ +------------------[/go]

(;GM[1]FF[4]CA[UTF-8]ST[2]
RU[Japanese]SZ[9]
PB[Black]PW[White]AW[be][ce][ee][fe][gf][hg][hh]AB[bg][cg][fh]
;W[dh]C[The obvious vital point]
(;B[eg]C[necessary]
(;W[fi]C[already less obvious]
(;B[eh]C[harder and harder]
(;W[ch]C[going uphill]
(;B[di]C[actually, its a mountain]
(;W[bh]C[now, it is straightforward, except for guessing the end result]
;B[dg]
;W[bi]
;B[gi]C[preparation for chosei]
;W[gh]
(;B[ci]C[forced]
(;W[ei]C[forced again, or else]
;B[di]
;W[fi]
;B[ci]C[Chosei (eternal life) : superko (like an ordinary ko for AGA or BGA rules : this move is not allowed , and Black must find the first threat.With japanese rules, the game is voided)])
(;W[hi]
;B[ei]C[Black is alive]))
(;B[ei]
;W[ci]C[Black is already dead]))
(;W[ci]
;B[ei]
;W[bh]
(;B[bi]C[not an easy refutation]
(;W[ah]
;B[ag])
(;W[ai]
;B[ag]
;W[ah]
;B[dg]))
(;B[ah]
;W[bi]C[Black is dead])))
(;B[ei]
(;W[dg]C[the only refutation]
;B[df]
;W[ef]
;B[cf]
;W[bh]
;B[ah]
;W[bf])
(;W[bh]
;B[dg]
;W[bi]
;B[ci]
;W[ag]
;B[af]
;W[ah]
;B[di]))
(;B[bh]
;W[ag]
;B[ah]
;W[di]
(;B[ei]
;W[bi]
;B[dg]
;W[ci]
;B[gh]
;W[gi]
;B[hi]
;W[gi])
(;B[bi]
;W[ei]
;B[bf]
;W[af]
;B[ae]
;W[af])))
(;W[ei]
;B[gi]
;W[di]
;B[gh]
;W[dg]
;B[df]))
(;B[gi]
;W[dg]
;B[df]
;W[ef]
;B[cf]
;W[fg]
;B[eh]
;W[gh]
;B[ei]
;W[di])
(;B[ei]
;W[eh]
;B[gi]
;W[dg]
;B[df]
;W[ef]
;B[fg]
;W[cf]
;B[ch]
;W[de]
;B[di]
;W[df])
(;B[dg]
;W[ei]
;B[ch]
;W[di]))
(;W[gh]
;B[eh]
;W[ch]
;B[bh]))
(;B[dg]
;W[eh]
;B[eg]
;W[fg]))

[cyclops]

$$c Black to live or make a ko i suppose.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . O . O X X O O . . . . . . . . . . . |
$$ | . X . X X O X X O . . . . . . . . . . |
$$ | . O X X O O . . O , . . . . . , . . . |
$$ | . O O O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

[go]$$c Black to live or make a ko i suppose.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . O . O X X O O . . . . . . . . . . . |
$$ | . X . X X O X X O . . . . . . . . . . |
$$ | . O X X O O . . O , . . . . . , . . . |
$$ | . O O O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Herman solved this intriguing tsumego in the forward drive. How about going in reverse drive.

$$c W to move
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . a . O X X O O . . . . . . . . . . . |
$$ | . X . X X O X X O . . . . . . . . . . |
$$ | . O X X O O . . O , . . . . . , . . . |
$$ | . O O O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

[go]$$c W to move
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . a . O X X O O . . . . . . . . . . . |
$$ | . X . X X O X X O . . . . . . . . . . |
$$ | . O X X O O . . O , . . . . . , . . . |
$$ | . O O O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

It seems Wa is the only move to prevent unconditional black live. So this diagram solves the tsumego backwards. How far can we thus rewind the position?
Is reverse tsumego a respectable aberation? Or should I seek help? Had it a name already?
And then what about allowing tenuki ? ( But not two consecutive tenuki, and only if alternate reversing is impossible )