Re: Problem Nr. 344 from Cho's intermediate Problems
Posted: Tue Nov 01, 2011 11:43 am
by Marcus
@Herman: Interesting. Now I need to figure out what I missed.
Re: Problem Nr. 344 from Cho's intermediate Problems
Posted: Tue Nov 01, 2011 12:14 pm
by tetron
Bill Spight wrote:
cyclops wrote: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 , . $$ | . O O O . . . a . . . $$ | . . . . . . . . . . .
[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'.
Re: Problem Nr. 344 from Cho's intermediate Problems
Posted: Tue Nov 01, 2011 1:00 pm
by jts
Marcus wrote:I leave continuations and alternate variations to the viewer.
Re: Problem Nr. 344 from Cho's intermediate Problems
Posted: Tue Nov 01, 2011 1:12 pm
by Marcus
jts wrote:
Marcus wrote: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 . . . $$ ----------------------
[go]$$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 . . . $$ ----------------------
[go]$$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.
Re: Problem Nr. 344 from Cho's intermediate Problems
Posted: Tue Nov 01, 2011 4:33 pm
by cyclops
jts wrote:
$$W White to kill $$ | . . . . . . . . . . . $$ | . . . . . . . . . . . $$ | . W . . . . . . . . . $$ | . . O O O O O O . , . $$ | O O X X . X X O . . . $$ | X X . X . . X O . W . $$ | X X . . . . . X . . . $$ ----------------------
[go]$$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]
HermanHiddema wrote:@jts: That's not a modern problem! ......
[go]$$W White to play $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . . . . . . . . . $$ | . O O . O O . . . $$ | . . . . . . O . . $$ | . X X . . . . O . $$ | . . . . . X . O . $$ | . . . . . . . . . $$ +------------------[/go]
(;GM[1]FF[4]CA[UTF-8]ST[2] RU[Japanese]SZ[9] PB[Black]PW[White]AW[be][ce][ee][fe][gf][hg][hh]AB[bg][cg][fh] ;W[dh]C[The obvious vital point] (;B[eg]C[necessary] (;W[fi]C[already less obvious] (;B[eh]C[harder and harder] (;W[ch]C[going uphill] (;B[di]C[actually, its a mountain] (;W[bh]C[now, it is straightforward, except for guessing the end result] ;B[dg] ;W[bi] ;B[gi]C[preparation for chosei] ;W[gh] (;B[ci]C[forced] (;W[ei]C[forced again, or else] ;B[di] ;W[fi] ;B[ci]C[Chosei (eternal life) : superko (like an ordinary ko for AGA or BGA rules : this move is not allowed , and Black must find the first threat.With japanese rules, the game is voided)]) (;W[hi] ;B[ei]C[Black is alive])) (;B[ei] ;W[ci]C[Black is already dead])) (;W[ci] ;B[ei] ;W[bh] (;B[bi]C[not an easy refutation] (;W[ah] ;B[ag]) (;W[ai] ;B[ag] ;W[ah] ;B[dg])) (;B[ah] ;W[bi]C[Black is dead]))) (;B[ei] (;W[dg]C[the only refutation] ;B[df] ;W[ef] ;B[cf] ;W[bh] ;B[ah] ;W[bf]) (;W[bh] ;B[dg] ;W[bi] ;B[ci] ;W[ag] ;B[af] ;W[ah] ;B[di])) (;B[bh] ;W[ag] ;B[ah] ;W[di] (;B[ei] ;W[bi] ;B[dg] ;W[ci] ;B[gh] ;W[gi] ;B[hi] ;W[gi]) (;B[bi] ;W[ei] ;B[bf] ;W[af] ;B[ae] ;W[af]))) (;W[ei] ;B[gi] ;W[di] ;B[gh] ;W[dg] ;B[df])) (;B[gi] ;W[dg] ;B[df] ;W[ef] ;B[cf] ;W[fg] ;B[eh] ;W[gh] ;B[ei] ;W[di]) (;B[ei] ;W[eh] ;B[gi] ;W[dg] ;B[df] ;W[ef] ;B[fg] ;W[cf] ;B[ch] ;W[de] ;B[di] ;W[df]) (;B[dg] ;W[ei] ;B[ch] ;W[di])) (;W[gh] ;B[eh] ;W[ch] ;B[bh])) (;B[dg] ;W[eh] ;B[eg] ;W[fg]))
reverse tsumego
Posted: Sun Nov 06, 2011 6:37 pm
by cyclops
Nagilum wrote:
$$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]$$c Black to live or make a ko i suppose. $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . 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 . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------
[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 )
......
Had it a name already?