Net versus ladder

    Keywords: Tactics

In general, capturing a stone in a net is considered better than capturing it in a ladder, because a net does not run the risk of a ladder block on the other side of the board.

There are exceptions to this rule, mostly when the extra liberty that a net gives is detrimental, in which case a ladder is quicker (the opponent is in atari until the end).

Table of contents Table of diagrams
White cuts
Net continuation
Ladder continuation
Taisha variation
Net continuation
Ladder continuation
Play firmly

Example

[Diagram]
White cuts  

When white cuts at W1, black can capture this stone in a ladder or in a net.

[Diagram]
Net continuation  

[problem- can't this net be defeated by the sequence c-d-e-f-g? sorry for poor notation.]

No, see here "White can't cut...". Black plays at g instead of f. White has no choice but to capture at f; B at h forces white to fill in at B2 and a couple more black moves capture the whole thing.

[Diagram]
Ladder continuation  

The net is better, because the ladder variation allows white to play a ladder block somewhere along the path of the ladder

Tapir: Even if there is no ladder breaker played by White, Black needs to capture at a time just in case. That is what I took from Kageyama: to capture with a ladder you need two moves, to capture with a net only one.

Example of exception

[Diagram]
Taisha variation  

In this variation of the taisha joseki. What the books say is that W7 is only playable when the ladder at a is good for White, capturing the stone B2 with the net White b and c isn't enough.

[Diagram]
Net continuation  
[Diagram]
Ladder continuation  

If the net continuation were good, White could play at W7 in the setup diagram independent of the ladder, thereby avoiding the most difficult variations.

After these plays, however, Black has a good result, and the possibility of a black peep at d remains. Also B4 forces W5. Both of these effects are there because the marked black stone is still on the board.

For comparison, see the usual result from the ladder variation. White's capture in the ladder forces B4.

(Note that the standard mistake here is White at a before W1: this loses sente and is an example of ignoring the 123 principle.)

Related concept

There is also an interesting tidbit in "Lessons in the Fundamentals of Go" by Kageyama. He states that when there are two ways to capture with one move, then the firmer is correct (choose the firmer capture).

[Diagram]
Play firmly  

In this example the two white stones can be captured with a geta by playing at a. However, according to Kageyama, the correct move is b, which has a firmer grip on the two stones.

--ArnoHollosi



Alex Weldon: There's something about this proverb that bothers me. Unless he also gives an objective definition of what "firmer" means (less liberties? That can't be it, or else a ladder would be "firmer" than a geta), I would read "firmer" to mean "with least aji." But since aji is bad potential, this just boils down to "Given a choice between two methods of capturing, the one that leaves the least bad potential is better," which is starting to sound an awful lot like a circular argument.

DJ: Alex, I think you're basically right (and I do not see any circularity...): I believe firmer does mean with good aji (see also my comments at Non local move versus a local move).

Alex Weldon: The circularity is not in defining "firmness" as "with good aji." The circularity is in stating that out of two ways of capturing a stone (or stones), the firmer way is better. On the surface, it sounds like wisdom, but it boils down to "out of two ways to capture a stone (or stones), the one with better aji is better," which is a tautology.

Gregory Wonderwheel: Unless "firmer" has a special meaning in Japanese Go jargon, at face value of the proverb, I take "firmer" to mean "with less cutting points" because that would reduce the number of possibilities for peeps before the capture, thus reducing the options for the opponent. Thus a short ladder could be firmer than a large net, and vice versa, a small net is more likely to be firmer than a long ladder.


Dieter: I believe there is this trade-off with ladders and nets.

  • Ladders have long-range aji, nets have short-range aji.
  • A ladder breaker (being the ladder aji put to use) can be answered once and the aji is gone. After a peep (the aji of a net put to use) is answered, the aji of another peep still exists.

I believe Kageyama's statement is that the long-range effect of a ladder in general is a heavier burden than the multiple short range aji of a net. As always with heuristics there are quite a few exceptions imaginable. In particular when the range of the ladder is rather short, it will most often be preferred over the net.

BTW, I would not call "the one with better aji is better" a circular statement, but I agree it just shifts the problem to the definition of good aji.


Notochord: Only if you consider aji to be the only characteristic of a position, which is stretching the definition a mite too far, I think. The point is essentially that the issue of aji, of giving those (most usually cutting) stones as little room to maneuver as possible, is often by far the most pressing concern. You should as a general rule play as tightly as possible, and avoid thinking that any move that succesfully makes a capture is just as good for the purpose of capturing as is any other move which does the same. As something of a corellary, I think that a main idea of the statement (Proverb?) is that we should not try to stretch our shape too much in capturing vital stones, in order to (for instance) reach towards some other position, and thus make our move 'less gote', since this usually creates a great deal of bad aji for the opponent to exploit which overwhelms the minor gains made from making a looser, weakly double-purpose capture.

Tactical discussion of Kageyama's example



Net versus ladder last edited by 207.138.202.112 on April 8, 2013 - 00:22
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