Interesting real game problem

illluck · #1

I played the below game on goshrine last night and thought the position at the end of the game was interesting enough that I'd like to share it (I would also greatly appreciate any comments on the game itself).

Comments to follow on next post as my current laptop has issues with scrolling while writing longer posts.

Kirby · #2

It doesn't appear that you've used an SGF for the game record.

illluck · #3

Hehe, yes, apologies. Should have used preview beforehand. Working now.

It is very fortunate that DGS has a converter to diagrams - I find it slightly difficult to have a logical flow using the eidogo viewer for analysis with multiple variations.

Click Here To Show Diagram Code: [go]$$Bc $$ -------------------------------------- $$ |. . . . . . . . . . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ |. . X . O X O O . . O O O X X X X . .| $$ |. . X O . O X . . , . X O O O O X . .| $$ |. . X . . . . . X . . . . O X X X . .| $$ |. . X O . . . O O X X X X X O O O X .| $$ |. X O O . . O . . . X O X . X O . . .| $$ |. O X O . . O X X X O O O X . . O X .| $$ |. . X O O X O X X O O O X X O O X . .| $$ |. O O X X . X X O O . . . . O X . X .| $$ |. . X X . X . O X . . . X . O X . . .| $$ |. . X . O O X O X . . . . . . . . . .| $$ |. O X X X O X O . . . O . O . . . . .| $$ |. X O X O O . . . . . . . . . O O . .| $$ |. O O . . . . . . . . X . . . . X . .| $$ |. . . O . O O O . , O X . . O O X . .| $$ |. . X . . X X O X O . O X X . X X . .| $$ |. . . X . . X X O . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ --------------------------------------[/go]

This is the position at the end of the game. My opponent ran out of time here.

illluck · #4

The position is white to play, and it appears as if the turn at J7 is the only move. The reason is that any other move appears to allow white a fairly easy sente eye:

The below sequence is an example of the sequence with white L8 instead (it can be verified that white playing L9 also gives black at least an eye in sente through the same idea).

Click Here To Show Diagram Code: [go]$$Wc $$ -------------------------------------- $$ |. . . . . . . . . . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ |. . X . O X O O . . O O O X X X X . .| $$ |. . X O . O X . . , . X O O O O X . .| $$ |. . X . . . . . X . . . . O X X X . .| $$ |. . X O . . . O O X X X X X O O O X .| $$ |. X O O . . O . . . X O X . X O . . .| $$ |. O X O . . O X X X O O O X . . O X .| $$ |. . X O O X O X X O O O X X O O X . .| $$ |. O O X X . X X O O . 4 . 0 O X . X .| $$ |. . X X . X . O X 3 2 . X 8 O X . . .| $$ |. . X . O O X O X 5 1 . . 7 6 9 . . .| $$ |. O X X X O X O . . . O . O . . . . .| $$ |. X O X O O . . . . . . . . . O O . .| $$ |. O O . . . . . . . . X . . . . X . .| $$ |. . . O . O O O . , O X . . O O X . .| $$ |. . X . . X X O X O . O X X . X X . .| $$ |. . . X . . X X O . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ --------------------------------------[/go]

White has to capture or connect after black 10.

This is pretty much a one-way street. Note that black plays 4 directly rather than cutting at K8 as it leaves an additional ko threat later.

illluck · #5

Having established that there would be a sente eye if black does not play J7, we now turn to the top, where there is a potential for a gote eye.

Click Here To Show Diagram Code: [go]$$Wc $$ -------------------------------------- $$ |. . . . . . . . . . . . . . . . . . .| $$ |. . . . . d . . 4 5 . . . . . . . . .| $$ |. . X . O X O O 6 a O O O X X X X . .| $$ |. . X O . O X b . 2 3 X O O O O X . .| $$ |. . X . . . . c X . . . . O X X X . .| $$ |. . X O . . . O O X X X X X O O O X .| $$ |. X O O . . O . . . X O X . X O . . .| $$ |. O X O . . O X X X O O O X . . O X .| $$ |. . X O O X O X X O O O X X O O X . .| $$ |. O O X X . X X O O . . . . O X . X .| $$ |. . X X . X . O X . 1 . X . O X . . .| $$ |. . X . O O X O X . . . . . . . . . .| $$ |. O X X X O X O . . . O . O . . . . .| $$ |. X O X O O . . . . . . . . . O O . .| $$ |. O O . . . . . . . . X . . . . X . .| $$ |. . . O . O O O . , O X . . O O X . .| $$ |. . X . . X X O X O . O X X . X X . .| $$ |. . . X . . X X O . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ --------------------------------------[/go]

Black 2 threatens to make an eye, and white 3 is the only way for white to prevent the gote eye (which, in combination with the sente eye sequence shown below, allows black to live).

The above sequence is again pretty much forced. Now white has a few choices. The key here is that white must live locally, as black's liberties will win any capturing race. Furthermore, the abundance of black's ko threats and the fact that any ko for life would be quite heavy means that white's life must be unconditional. To make matters worse, the aji of F17 means that white also has to be careful about not allowing black to get "a" in sente (as then black "b" makes miai of "c" and "d").

Below are some of white's possible local moves:

Click Here To Show Diagram Code: [go]$$Bc $$ -------------------------------------- $$ |. . . . . . . . . . a a . . . . . . .| $$ |. . . . . . . . X O . c . a . . . . .| $$ |. . X . O X O O X . O O O X X X X . .| $$ |. . X O . O X b . X O X O O O O X . .| $$ |. . X . . . . . X . . . . O X X X . .| $$ |. . X O . . . O O X X X X X O O O X .| $$ |. X O O . . O . . . X O X . X O . . .| $$ |. O X O . . O X X X O O O X . . O X .| $$ |. . X O O X O X X O O O X X O O X . .| $$ |. O O X X . X X O O . . . . O X . X .| $$ |. . X X . X . O X . O . X . O X . . .| $$ |. . X . O O X O X . . . . . . . . . .| $$ |. O X X X O X O . . . O . O . . . . .| $$ |. X O X O O . . . . . . . . . O O . .| $$ |. O O . . . . . . . . X . . . . X . .| $$ |. . . O . O O O . , O X . . O O X . .| $$ |. . X . . X X O X O . O X X . X X . .| $$ |. . . X . . X X O . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ --------------------------------------[/go]

First of all, any of the points marked "a" allows black K17 as sente and gives the gote eye through miai (as discussed above). Refer below for a representative sample (it can be verified that the other two points also makes K17 sente):

Click Here To Show Diagram Code: [go]$$Wc $$ -------------------------------------- $$ |. . . . . . . . . . 1 9 . 0 . . . . .| $$ |. . . . . . . . X O . 4 5 7 8 . . . .| $$ |. . X . O X O O X 2 O O O X X X X . .| $$ |. . X O . O X 3 . X O X O O O O X . .| $$ |. . X . . . . . X . . 6 . O X X X . .| $$ |. . X O . . . O O X X X X X O O O X .| $$ |. X O O . . O . . . X O X . X O . . .| $$ |. O X O . . O X X X O O O X . . O X .| $$ |. . X O O X O X X O O O X X O O X . .| $$ |. O O X X . X X O O . . . . O X . X .| $$ |. . X X . X . O X . O . X . O X . . .| $$ |. . X . O O X O X . . . . . . . . . .| $$ |. O X X X O X O . . . O . O . . . . .| $$ |. X O X O O . . . . . . . . . O O . .| $$ |. O O . . . . . . . . X . . . . X . .| $$ |. . . O . O O O . , O X . . O O X . .| $$ |. . X . . X X O X O . O X X . X X . .| $$ |. . . X . . X X O . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ --------------------------------------[/go]

The point "b" aims to remove the eye threatened by k17, but is easily refuted by black descending at O18 and killing the group.

Therefore, the point "c" is the strongest local resistance.

illluck · #6

In response to "c", black can play K17 as that forces white to remove the eye possibility. Then black atari at K19 is ko (which, given the number of moves that threats to live for black and the fact that white has to live if black wins the ko, means that black is effectively alive).

Click Here To Show Diagram Code: [go]$$Wc $$ -------------------------------------- $$ |. . . . . . . . . 4 5 . . . . . . . .| $$ |. . . . . . . . X O 6 1 . . . . . . .| $$ |. . X . O X O O X 2 O O O X X X X . .| $$ |. . X O . O X 3 . X O X O O O O X . .| $$ |. . X . . . . . X . . . . O X X X . .| $$ |. . X O . . . O O X X X X X O O O X .| $$ |. X O O . . O . . . X O X . X O . . .| $$ |. O X O . . O X X X O O O X . . O X .| $$ |. . X O O X O X X O O O X X O O X . .| $$ |. O O X X . X X O O . . . . O X . X .| $$ |. . X X . X . O X . O . X . O X . . .| $$ |. . X . O O X O X . . . . . . . . . .| $$ |. O X X X O X O . . . O . O . . . . .| $$ |. X O X O O . . . . . . . . . O O . .| $$ |. O O . . . . . . . . X . . . . X . .| $$ |. . . O . O O O . , O X . . O O X . .| $$ |. . X . . X X O X O . O X X . X X . .| $$ |. . . X . . X X O . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ --------------------------------------[/go]

Given the above variations and the fact that pretty much move is sente for black (meaning that black doesn't have to play out the sente eye near the middle first, leaving more ko threats), we can almost conclude that any white first move other than J7 fails. There are just two more possible resistances to consider:

Click Here To Show Diagram Code: [go]$$Wc $$ -------------------------------------- $$ |. . . . . . . . . . . . . . . . . . .| $$ |. . . a . b . . X O . . . . . . . . .| $$ |. . X . O X O O X . O O O X X X X . .| $$ |. . X O . O X . . X O X O O O O X . .| $$ |. . X . . . . . X . . . . O X X X . .| $$ |. . X O . . . O O X X X X X O O O X .| $$ |. X O O . . O . . . X O X . X O . . .| $$ |. O X O . . O X X X O O O X . . O X .| $$ |. . X O O X O X X O O O X X O O X . .| $$ |. O O X X . X X O O . . . . O X . X .| $$ |. . X X . X . O X . O . X . O X . . .| $$ |. . X . O O X O X . . . . . . . . . .| $$ |. O X X X O X O . . . O . O . . . . .| $$ |. X O X O O . . . . . . . . . O O . .| $$ |. O O . . . . . . . . X . . . . X . .| $$ |. . . O . O O O . , O X . . O O X . .| $$ |. . X . . X X O X O . O X X . X X . .| $$ |. . . X . . X X O . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ --------------------------------------[/go]

First of all, "a" is sente against the top left (if black tenuki, white kills by jumping into the corner). However, it seems like "a" is too far to affect the situation. It can be verified that it doesn't even make H16 harder to deal with as the descent at K19 is still not threat to connect. Furthermore, black does not have to answer as killing the top is worth more than the corner (i.e. already better compared to white allowing the gote eye in terms of points, not to mention that white now ends in sente as black has to kill corner).

"b" is a bit more interesting compared to H16 as it DOES make K19 sente, but white still ends up a move short:

Click Here To Show Diagram Code: [go]$$Wc $$ -------------------------------------- $$ |. . . . . . . . 4 3 . 6 . . . . . . .| $$ |. . . . . 1 . . X O . . . 2 . . . . .| $$ |. . X . O X O O X . O O O X X X X . .| $$ |. . X O . O X . . X O X O O O O X . .| $$ |. . X . . . . . X . . 5 . O X X X . .| $$ |. . X O . . . O O X X X X X O O O X .| $$ |. X O O . . O . . . X O X . X O . . .| $$ |. O X O . . O X X X O O O X . . O X .| $$ |. . X O O X O X X O O O X X O O X . .| $$ |. O O X X . X X O O . . . . O X . X .| $$ |. . X X . X . O X . O . X . O X . . .| $$ |. . X . O O X O X . . . . . . . . . .| $$ |. O X X X O X O . . . O . O . . . . .| $$ |. X O X O O . . . . . . . . . O O . .| $$ |. O O . . . . . . . . X . . . . X . .| $$ |. . . O . O O O . , O X . . O O X . .| $$ |. . X . . X X O X O . O X X . X X . .| $$ |. . . X . . X X O . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ --------------------------------------[/go]

So, after examining all the above variations, I believe it's safe to conclude that J7 is the only move for white.

illluck · #7

We are finally getting to the main sequence.

Unfortunately, at this point I realize that I made a horrible mistake - the sente eye sequence works still even if white plays J7, making all my reading (and my joy at finding the "tesuji") moot.

Click Here To Show Diagram Code: [go]$$Wc $$ -------------------------------------- $$ |. . . . . . . . . . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ |. . X . O X O O . . O O O X X X X . .| $$ |. . X O . O X . . , . X O O O O X . .| $$ |. . X . . . . . X . . . . O X X X . .| $$ |. . X O . . . O O X X X X X O O O X .| $$ |. X O O . . O . . . X O X . X O . . .| $$ |. O X O . . O X X X O O O X . . O X .| $$ |. . X O O X O X X O O O X X O O X . .| $$ |. O O X X . X X O O . 4 . . O X . X .| $$ |. . X X . X . O X 3 2 . X . O X . . .| $$ |. . X . O O X O X 5 . . . . 6 . . . .| $$ |. O X X X O X O 1 . . O . O . . . . .| $$ |. X O X O O . . . . . . . . . O O . .| $$ |. O O . . . . . . . . X . . . . X . .| $$ |. . . O . O O O . , O X . . O O X . .| $$ |. . X . . X X O X O . O X X . X X . .| $$ |. . . X . . X X O . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ --------------------------------------[/go]

In case anyone is curious, the below is my original intent during the game:

Click Here To Show Diagram Code: [go]$$Wc $$ -------------------------------------- $$ |. . . . . . . . . . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ |. . X . O X O O . . O O O X X X X . .| $$ |. . X O . O X . . , . X O O O O X . .| $$ |. . X . . . . . X . . . . O X X X . .| $$ |. . X O . . . O O X X X X X O O O X .| $$ |. X O O . . O . . . X O X . X O . . .| $$ |. O X O . . O X X X O O O X . . O X .| $$ |. . X O O X O X X O O O X X O O X . .| $$ |. O O X X . X X O O . . . . O X . X .| $$ |. . X X . X . O X . . . X . O X . . .| $$ |. . X . O O X O X . . . . . . . . . .| $$ |. O X X X O X O 1 . . O 2 O . . . . .| $$ |. X O X O O . . . . . . . . . O O . .| $$ |. O O . . . . . . . . X . . . . X . .| $$ |. . . O . O O O . , O X . . O O X . .| $$ |. . X . . X X O X O . O X X . X X . .| $$ |. . . X . . X X O . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ --------------------------------------[/go]

Black connects if white doesn't atari, and has the below sequence if white plays the atari above:

Click Here To Show Diagram Code: [go]$$Wc $$ -------------------------------------- $$ |. . . . . . . . . . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ |. . X . O X O O . . O O O X X X X . .| $$ |. . X O . O X . . , . X O O O O X . .| $$ |. . X . . . . . X . . . . O X X X . .| $$ |. . X O . . . O O X X X X X O O O X .| $$ |. X O O . . O . . . X O X . X O . . .| $$ |. O X O . . O X X X O O O X . . O X .| $$ |. . X O O X O X X O O O X X O O X . .| $$ |. O O X X . X X O O . 6 . . O X . X .| $$ |. . X X . X . O X . 7 . X 9 O X . . .| $$ |. . X . O O X O X . . 5 3 4 8 0 . . .| $$ |. O X X X O X O 1 . . O 2 O . . . . .| $$ |. X O X O O . . . . . . . . . O O . .| $$ |. O O . . . . . . . . X . . . . X . .| $$ |. . . O . O O O . , O X . . O O X . .| $$ |. . X . . X X O X O . O X X . X X . .| $$ |. . . X . . X X O . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ --------------------------------------[/go]

Therefore, black has no choice but to atari from below, and white can then at least live with the same sente eye sequence. (White should get the top eye trade in first so that black can't resist with ko at the top):

Click Here To Show Diagram Code: [go]$$Wc $$ -------------------------------------- $$ |. . . . . . . . . . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ |. . X . O X O O . . O O O X X X X . .| $$ |. . X O . O X . . , . X O O O O X . .| $$ |. . X . . . . . X . . . . O X X X . .| $$ |. . X O . . . O O X X X X X O O O X .| $$ |. X O O . . O . . . X O X . X O . . .| $$ |. O X O . . O X X X O O O X . . O X .| $$ |. . X O O X O X X O O O X X O O X . .| $$ |. O O X X . X X O O . 8 . . O X . X .| $$ |. . X X . X . O X 7 6 . X . O X . . .| $$ |. . X . O O X O X 9 . . 4 . 0 . . . .| $$ |. O X X X O X O 1 . . O 2 O . . . . .| $$ |. X O X O O . . . . . . 3 5 . O O . .| $$ |. O O . . . . . . . . X . . . . X . .| $$ |. . . O . O O O . , O X . . O O X . .| $$ |. . X . . X X O X O . O X X . X X . .| $$ |. . . X . . X X O . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ --------------------------------------[/go]

If 5 doesn't protect the cut on the right side, black lives rather easily.

Click Here To Show Diagram Code: [go]$$Wc $$ -------------------------------------- $$ |. . . . . . . . . . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ |. . X . O X O O . . O O O X X X X . .| $$ |. . X O . O X . . , . X O O O O X . .| $$ |. . X . . . . . X . . . . O X X X . .| $$ |. . X O . . . O O X X X X X O O O X .| $$ |. X O O . . O . . . X O X . X O . . .| $$ |. O X O . . O X X X O O O X b . O X .| $$ |. . X O O X O X X O O O X X O O X . .| $$ |. O O X X . X X O O . . . . O X . X .| $$ |. . X X . X . O X . . . X 8 O X . . .| $$ |. . X . O O X O X . . . 4 7 6 9 . . .| $$ |. O X X X O X O 1 . . O 2 O 0 . . . .| $$ |. X O X O O . . . . . 5 3 a . O O . .| $$ |. O O . . . . . . . . X . . . . X . .| $$ |. . . O . O O O . , O X . . O O X . .| $$ |. . X . . X X O X O . O X X . X X . .| $$ |. . . X . . X X O . . . . . . . . . .| $$ |. . . . . . . . . . . . . . . . . . .| $$ --------------------------------------[/go]

Black captures with "b" after white "a".

SmoothOper · #8

That is interesting. Recently I have had a number of wins on time playing san-san, have you noticed this phenomena too? I suspect it is the nature of some of the variations leading to low scoring complicated games that causes this. Here move 102 didn't work, I could have made life instead, however I was watching the clock and I knew they wouldn't be able to read it out in time.

Interesting real game problem

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