light ko

  Difficulty: Intermediate   Keywords: Ko, Go term

In game commentaries, one can read the phrase "this ko is light for Black". This means that losing the ko does not make a big difference for Black in this stage of the game, it is mostly a matter of points and not of strategic importance.

If a ko is light for both players, it means that the ko is simply small, such as a one point endgame ko. In such a context the term is seldom used. Mostly the context is one where the ko is light for one player, but heavy for the other.

Bill: This last paragraph sounds like a guess. As does a lot of this page. Jim Yu, I am sure, did a faithful translation, but this terminology is not generally used in English.

A ko is heavy for a player, if he can hardly afford to lose it. It has strategic conseuqences, such as a submissive follow up, which is not compensated by the ko-threat and its execution. For a clearly unilaterally favourable ko, we speak about a flower viewing ko.

If the ko is heavy for both players, then we speak about a game deciding ko

(Examples to be added - found regular usage of these terms, hence many examples in the "Analyzed Games of Go Seigen")

Dieter: Okay Bill, but it is used in the book. And I found it more intuitive than the whole komaster treatment. Sure a better job needs to be done describing these terms.

Bill: I am not objecting to the terminology, but I don't think that we can say much about its general usage in English. As for Chinese, I can't say anything at all. ;) I look forward to the examples, which should shed some light. :)

unkx80: This usage seems consistent in Chinese literature. As far as I understand, the "light" and "heavy" in "light ko" and "heavy ko" have the meanings as described in light and heavy respectively, i.e., one that can be easily sacrificed and one that cannot be easily sacrificed.

Bill: Very interesting, unkx80! :) Thanks. IIUC, a small ko is not necessarily light, then. Is that right?

unkx80: I guess, most small kos are light. My understanding is that the following applies to the Chinese as well:

If a ko is light for both players, it means that the ko is simply small, such as a one point endgame ko. In such a context the term is seldom used.

On the other hand, nobody would describe a game-deciding 1/3-point ko as "light".


Example

[Diagram]

Go Seigen - Fujisawa Kuranosuke - 1952 (141-148)

From Jim Yu's Analyzed games of Go Seigen?, Chapter 3. Go Seigen is White, Fujisawa Kuranosuke is Black.

"B141 suddenly throws out a violent attack. W is in a deeper trouble. W142 is the only move to find a way to escape.

B147 To here are sure moves by both sides. It has developed to such a situation that it seems impossible for W to unconditionally escape (without paying anything, that is).

W148: W is alrealy in extremely danger, but when W148 atari, ...

B149 connects without hesitation at white+circle. If this move were to connect at a, saving the B149 point as a ko, then it would be a light ko for Black. Thus the situation would be simplied, and White would be almost hopeless."



From the same game, a few moves later, an example of a heavy ko.

[Diagram]

Go Seigen - Fujisawa Kuranosuke - 1952 (157-148)

B161 @ black+circle

"B157: to cut this way is dangerous. Black a to connect, insisting to make a worry-free ko (light ko, --Dieter), is the most solid move. Now (...), this ko becomes heavy. That is, if B will lose the ko, he will have to pay."

(and in a variation Jim Yu explains why W160 must be played ...)

[Diagram]

Go Seigen - Fujisawa Kuranosuke - 1952 (157-148)

(in summary) If W160 captures black+circle, then the bottom left lives in ko, but it is a light ko for Black, so this is not an option for White.

(and attempting to clarify something which is confusingly stated in Yu's text) The ko is light on Black, because he has the options open to cut off the four stones on the left, with a, so the life of his group is never at stake.

[Diagram]

Variation

On the other hand, If Black plays B159 here, then White's capture tilts the balance of thickness into his favour. I can imagine a large scale cut & connect move at W162 which would next threaten both a and b.

--Dieter

Bill: Great work, Dieter! Thanks so much. :)

BTW, my guess is that a worry-free ko is the same thing as a flower viewing ko, which is the extreme form of a light ko.


This is a copy of the living page "light ko" at Sensei's Library.
(OC) 2011 the Authors, published under the OpenContent License V1.0.
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