Crosscut Then Extend / Technical Discussion

Sub-page of CrosscutThenExtend

Cross-cut? Then extend!

SAS: This is a really awful proverb. This page needs to be rewritten so that it doesn't start with something that makes it sound as if the proverb is reliable. (I've moved a different passage to the beginning now, but the page still needs a lot of work.)

Bill Spight's remark below may be correct; if the proverb were "If crosscut, consider extending", then it could be viewed as an antidote to the beginner habit of always playing atari. But see also Ishikura Noboru's remark quoted below that the proverb is only intended to apply when there are no other stones nearby --- a comparatively rare situation in practice.

Dieter: Given the evidence displayed here and elsewhere, I removed this proverb from the basic instinct page.

The following quote from Simon Goss (BGA 2-dan) is copied from another page:

Among mid-single-digit-kyus I seem to find lots examples of [...] extending out of every cross-cut, just because the proverb tells us that this is what is expected of all good citizens (read Richard Hunter's Crosscut Workshop to see just how feeble this is);

From Richard Hunter's Cross-cut Workshop (the BGJ series):

"Eh?" says Tsutsumi, "Shouldn't one extend from a cross-cut?". "No, no, no", cries Ishikura. "That's only when there are no other stones nearby."

See Strange Pro Opening 3 for a game illustrating the proverb in a situation where there are no other stones nearby.

Bill Spight: What does Richard Hunter have to say? Using Kombilo on an admittedly small database, it seems that pros atari a crosscut more often than they extend from it. Perhaps the value of the proverb lies in alerting players to the possibility of extending, rather than saying that it should be the usual response.

DaveSigaty: Bill, I had not thought of using Kombilo this way (I did not even realize it would generalize the search to this extent!). here is the result of a crosscut search on the GoGoD CD:

Pattern searched for:

Either Side Crosscuts  

I set the search without fixed color and without fixed anchor position so it looked for all games with this kind of crosscut position anywhere on the board with at least one layer of empty intersections all the way around it.
Continuations (either White or Black plays a or b):


Note that Kombilo seems to minimize the number of variations that it will report. Therefore it reuses a for example, reporting extensions as a black move at a and ataris as a white move at a.


2647 matches (2647/0), B: 53.4%, W: 43.1%

  • Ba: 779 (762) = 29%, B53.0% - W43.8%. Black extends at a in the diagram.
  • Wa: 1799 (1714) = 67%, B53.4% - W43.0%. White plays at a in the diagram, these are the atari plays that Bill mentions.
  • Bb: 59 (58), B57.6% - W39.0%. Black plays at b, away from the crosscut.
  • Wb: 2 (0), B50.0% - W50.0%. W plays at b(!), the only other spot in the search space.

Note that the numbers in parenthesis are the games where the next play in the game is the reply to the crosscut. Therefore there are 105 cases where the player with sente plays tenuki against the crosscut.

The total games searched was 13,841. Kombilo reported hits in 2379 games so about 17% of the games feature this pattern. There are more crosscuts found than games featuring them so about 10% such games have more than one crosscut.

Bill: Thanks, Dave, for doing a broader search. :-)

''(moved from LibraryLobby)

From the GoProverbs page: "Although proverbs often can help, you must always evaluate whether or not they apply in a particular situation - often there's more than one proverb which applies, sometimes they are even contradictory. Therefore, common sense must still be used." Some people seem to be in favour of discarding proverbs because, or if, they are not universally true. Bull, I say - proverbs are truths to be discovered first, rejected later, confirmed later still, etc. Basic Instinct is your baby, but personally I wouldn't remove it.

MortenPahle Hear hear. Proverbs are very much 'first options', always to be evaluated, and sometimes as antedotes to drag the focus away from a decidedly bad move which might otherwise seem natural. Go being Go, there is no universal truth. (I like that phrase, and will claim copyright to it unless someone else has said it before :^)

SAS: But what has this got to do with including "Cross-cut? Extend!" on the BasicInstinct page. If you read the introduction to that page, you'll see that it doesn't fit. Even "Cross-cut? Atari!" (which is more usually correct, if professional practice is anything to go by) would not fit. The basic instinct in reaction to a cross-cut should be to atari or extend.

MortenPahle: My 'Hear Hear' was aimed at Dieters comments on Proverbs in general. This is not the place to discuss the virtue of the 'extend from a crosscut' inclusion or not on the Basic Instincts page. You make an intersting point on professional practice which we may want to discuss, though.

Alex Weldon: Perhaps the best way to understand this proverb is negatively. That is, maybe we should create a Crosscut-Reasons to Atari page. Then we can just refer to that page, and say, "if you don't have a specific reason - such as one of these - to atari, then extension is best by the the 1-2-3 principle."

I would create the page and start listing reasons myself, but I'm in the computer lab at the university, and my class is starting in 10 minutes. I'm very busy these days, but if no one else gets to it, I'll do something later this week.

Crosscut Then Extend / Technical Discussion last edited by AlexWeldon on November 9, 2004 - 20:43
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