Stuck with a problem of kÃ´

oca · Post by **oca** » Wed Apr 02, 2014 9:01 am

Hello

I'm reading a book called "Le go pas à pas, 4 formes" by Fan Hui. (that means "go step by step, 4 shapes")

This is book consists mostly on problems, with very few text.
Solutions are provided, but without any more comments. Every thing was fine till I get to chapter 7 on Kô.
I 'm stuck still the first one and don't now what to do...

Click Here To Show Diagram Code: [go]$$Bc Black plays and kill white by ko $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . X . . . . . . . . . . $$ | . . X . . . . . . . . . $$ | . O X , . . . . . , . . $$ | . X O X X X . X . . . . $$ | X O O O O O X . . . . . $$ | . . . . . . . . . . . . $$ +------------------------[/go]

First I may tell you what I understand of kô for now...

Click Here To Show Diagram Code: [go]$$B $$ | . . . . . . . $$ | . . O O O . . $$ | O O X X O O . $$ | X X X a B O . $$ | . X . X O O . $$ +-------------[/go]

I understand that both black and white want to play at (a), black to live and white to kill...
I understand that there should be menaces (kô thearts) somewhere else on the board and that the first one who doesn't have a sufficient menace will lose
the fight and it's opponent will play at (a).

(I will hide now the rest of the post as it contains the solution, so if you want to try first, don't open now...)

peti29 · Post by **peti29** » Wed Apr 02, 2014 9:20 am

is right, it creates a KO.

White will play

at A-3 capturing your stone.

You must not play

at A-5 but somewhere else on the board (which is not shown on the diagram).
Where you play

must be a KO-threat: a move white can not afford to let unanswered.

This way if white answers your threat, then you can play

at B-3 to keep up the KO fight.
But now white will play a threat forcing you to answer so that you can't play B-5 to end the KO.

If you answer white's threat, white will again play at A-3...

This goes on and on until one of you run out of KO-threats (moves that force the opponent to answer otherwise they suffer a great loss) at which point one of the players will have "time" to end the KO.

Also note that KO threats will differ in "size". Those that threaten to take 1-2 points are easy to ignore, while those that threaten to kill entire corners are better answered.

Here the KO is much more favorable for black because if white loses the KO the whole white group will die. So it will be difficult for white to find a threat that is large enough to make black answer instead of ending the KO (by playing e.g. at B-5) and kill the white group.

I hope that I could help.

skydyr · Post by **skydyr** » Wed Apr 02, 2014 9:55 am

If you count it out, the ko is worth something in the neighborhood of 30 points, so if your opponent makes a ko threat that is worth less than 30 points when he follows up, it's better to finish the ko and give him those 20 points (for example) for a net gain of 10.

As mentioned, though, if black loses the ko, he doesn't lose much locally, maybe 4-6 points at most, but white stands to lose the whole group. As a result, black might be satisfied with a 15 point ko threat, for a 10 point gain or so, while white is struggling just to maintain the status quo. This is why the ko is favourable for black.

There are other kos where both sides stand to lose a great deal, like a group, which are much less biased in favour of one side or the other, or kos where one side needs to play a local follow up before finishing the ko, requiring them to ignore 2 ko threats to win, and counting these can get much more complicated.

Bill Spight · Post by **Bill Spight** » Wed Apr 02, 2014 10:16 am

I know the original is in French. The English is misleading.

Click Here To Show Diagram Code: [go]$$Bc Black plays and kill white by ko $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . X . . . . . . . . . . $$ | . . X . . . . . . . . . $$ | . O X , . . . . . , . . $$ | . X O X X X . X . . . . $$ | X O O O O O X . . . . . $$ | . . . . . . . . . . . . $$ +------------------------[/go]

Better would be something like this: Black to play and make ko to kill White. (Not that the ko would kill, but that it would if Black wins the fight.)

oca · Post by **oca** » Wed Apr 02, 2014 11:05 pm

@peti29

Thanks for your detailed reply, I got it now.
I was thinking that all the ko threats where on the diagram... but there are not...That what's a missed.
So it will be way more easy for me now

I will kill them all

@skydyr
Thanks, I understand that question of points, at least intellectually... For now, ko is still not part of my playing. I can still not identify them at"the right time". That's something I hope to be better at with a bit more playing.

For now I'm still answering "immediatly" the very few mistakes I saw... So I don't have that much threats to exploit (and loose sente to often ).

@Bill
The original directive in french is "Noir joue et tue Blanc par kô."
"Black to play and make ko to kill White" is really what I have to do.

Bill Spight · Post by **Bill Spight** » Wed Apr 02, 2014 11:58 pm

oca wrote: @Bill
The original directive in french is "Noir joue et tue Blanc par kô."
"Black to play and make ko to kill White" is really what I have to do.

Vive la France!

oca · Post by **oca** » Thu Apr 03, 2014 12:09 am

Actually, I'm from Switzerland.

Most part of swiss people (75%) speak german.
nearly 20% speak french.
and 5% speak italian.

A bit weird for a that small country...

Bill Spight · Post by **Bill Spight** » Thu Apr 03, 2014 5:36 am

Learn the apple piercing tesuji.

skydyr · Post by **skydyr** » Thu Apr 03, 2014 7:32 am

oca wrote: @skydyr
Thanks, I understand that question of points, at least intellectually... For now, ko is still not part of my playing. I can still not identify them at"the right time". That's something I hope to be better at with a bit more playing.

For now I'm still answering "immediatly" the very few mistakes I saw... So I don't have that much threats to exploit (and loose sente to often ).

It's definitely an acquired skill, and as you play more, you will get better at it. I think for a lot of players, until maybe mid SDK ko is something fearful and scary. After that, once you have a better handle on it, it becomes a weapon: "Sure, you can live there, but I get to take a couple free moves elsewhere in exchange" or "Go ahead, spend 3 moves killing my group. I can make it up easily". When strong players play ko, they often use sente endgame moves they wanted to play anyways as ko threats, making them do double work. When weak players (and I include myself here) play ko, they often end up playing ko threats that lose them points on the board, by removing aji or the like. For now, so long as you understand how ko works, in that one player makes a threat, then captures after it's responded to, and then the other player makes a threat, etc., you can ask people to review your games to get a more nuanced view of what was going on.

As for counting, while many people hear of it earlier, I don't know of anyone offhand who started counting seriously before the weak to mid-SDK level either. Until a certain point, games swing back and forth due to errors too much to make counting terribly useful. There's no point in knowing that X is worth 5 points and Y is worth 3 when one player accidentally kills his 20 point group, or there's a 15 point move neither player noticed on the board. It's good to be aware of, though, so that once you are ready it may pop into your head when you get to a tough situation as a way to figure out what to do.

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