Attempt. Moves 1-10
Herman Hiddema: Hmmm, looks bad for white. Here's an attempt which results in ko...
Attempt, moves 11-20
Herman Hiddema: [90] Black can also take the ko with . White can then play
as a ko threat, and after
white retakes the ko and we get basically the same result.
zinger: [100] Egads, black is risking alot by doing this! If I were black, I would just play at
in the first diagram, then work on the center with a - it looks like enough to win. Sorry for giving a counting reply to a tsumego problem, but after all, the whole board was posted :)
[110] tderz the left side is now worth
This variation is not playable with ! (
instead of a)
[120] tderz: better immediately the ko, as White could not connect with , she would be lost.
However, this ko is so big, that only internal ko threats could be valid?
[130] tderz: perhaps something like this (if now m or c, then something like n)
and living with the lower group, or simply c as threat.
Chris Hayashida: I got the idea that this was the sequence that Zinger suggested. While he did mark a on the second diagram, I think he was referring and
on the first diagram.
I'm not sure that this would be enough for Black. a, b, and c are all big points, and White has sente. When I was playing, I counted that White was ahead if his group survived. I probably need to re-evaluate this position to see if this is still the case.
zinger: Yes, this is what I meant. I count black ahead by about 10 points on the board, but then there's komi, and it's white's turn. So maybe it's about even. Still, I would do this rather than risk everything, and rely on my endgame. Besides, it looks like white lives anyway. Chris: did you win in the end? By how much?
Chris Hayashida: This is what I played during the tournament. I don't want to list it as a solution until it stands up against scrutiny from the other deshi. If it does, I'll move it to the solution subpage.
Chris Hayashida: [10] This took me five minutes to read out (during the tournament) and I finally played this sequence. It is a similar sequence to what was posted above, but I played atari with and saved the other moves for local ko threats.
Chris Hayashida: [20] If , then White throws in at
and catches the marked black stones in oiotoshi for a second eye. This is what happened in the game.
Chris Hayashida: [30] This was the variation that I wasn't as sure about. leads to ko, but I think White has a huge number of local threats, starting with
.
tderz: [32] a and b are miai - hence White cannot live without ko and must exploit (internal) ko threats c, d, else or in combination.
Chris Hayashida: [40] If Black plays to resolve the ko, then
again catches the marked black stones in oiotoshi for the second eye.
tderz: [42] Above (over)kills a dead white group.
White lives, hence Black did not achieve much else than putting stones in his own territory.
Chris Hayashida: [50] If Black responds to White's threat with , then White will retake the ko with
. I think White can ignore almost any threat and play
. If Black ignores
, then both groups live with
. I believe this is bigger than any other threat on the board.
Chris Hayashida: [60] I think is forced. Answering the ko threat at a is not big enough, so White must play the ko with
. I don't think Black has a big enough ko threat.
Tderz Just comparing the two diagrams [10] and the one above (I did not check the game at all, which would be necessary to decide which strategy is eventually necessary), Black could (better?) consider to play this immediately in above diagram [10] (see below [70]), thereby taking much aji out of the position, capturing White and accepting the upper result , but not playing a ko about the lower..
[70] tderz Black allows White with dia. [20] to live with the bigger group, as can be seen in dia. [40]. Black doesn't want to give White such a choice and should therefore (IMO) connect directly with .
Chris Hayashida: By my count, this variation still has White ahead (including 6.5 komi.) What do you think?
tderz I didn't count - as I stated before - and I do not dare to. Perhaps I should then not give any commentary at all, and as soon as ko is involved, commenting would not make much sense.
Above I just compared two diagrams, this [70] with [20] and [30].
Analysis: seems bigger than
.
is perhaps still bigger than the white upper left corner, even if it survives by capturing two stones ([50], [60] where Black loses everything). >Hence, I wanted to conclude that capturing the bigger group makes more sense than any ko [30] where one overkills the already dead & smaller group or capturing the smaller
in exchange.
If White still is leading, so be it! Often analyzing and going through games can show many options & alternatives, but not a clear way to win. Most probably there were many options to make easier better moves earlier on.