Should black pass in this situation?

Question

Suppose a game of go ends up in the follow position, with black to play. (Assume everything is settled apart from the situation in the centre of the board.)

As black it seems like there's no productive move for me to make. I can't play at the point marked with a square because I'll be captured, and if I play at the triangle point I'm playing into my own territory, which loses a point (assuming Japanese rules). So it seems like I should pass.

But if I do pass, then white will play at the point marked with a square, and I'll have to play on the triangle point anyway. Then both players will pass, and the result will be the same as if I just played at the triangle to start with.

I'm still a beginner (11 kyu on OGS), so I'm wondering how this would normally be handled in a game between stronger players. Would black pass or play at the triangle point, and how would white respond?

I'm interested both in whether there's anything I've missed about this question, and in the etiquette around when to pass. I'd also be interested to learn if the difference between Japanese and Chinese rules changes anything about this situation.

Answer 1

The marked spaces are what's called dame they are empty spaces that are of no interest to either white or black because the spaces will not effect the outcome of the game and do not need to be filled to determine the winner. In a casual game, I think it is worthwhile to simply ask your opponent if they agree with your own assessment of a group of stones when you're deciding whether to pass or not.

If it was two reasonably experienced players in a situation like this, I think they would likely pass and regard the black stone and marked spaces as unclaimed. Resulting in 24 points for black and 30 points for white under the Japanese scoring system and 36 for black and 43 for white under the Chinese system (feel free to check my math for the Chinese score).

If the players could not agree that the black stone and two marked spaces are of no value, the players could keep going and play it out. Playing more stones will change the final score, but in a situation where the fate of the stones are truly already determined regardless of play, it will not have an impact on the difference between the scores. For example, if black did play a stone at the triangle space and white played at the square, then the Japanese score would be the same and the Chinese score would be 37 for black and 44 for white. Either way the gap between the scores would remain the same.

This article at Sensei Library has a section on dame and neutral spaces. It summarizes the difference between the scoring systems as:

With Territory Scoring:

There are no points in playing Dame
Playing in your own territory reduces your score.
(It covers an empty point.) 

With Area Scoring:

Playing a Dame point is worth a point
(it puts a stone of your color on the board).
Playing in your own territory doesn't affect your score. 

Answer 2

The intersection marked with a triangle is usually called a teire: an intersection within Black's territory, but which Black will have to fill before the end of the game.

The description of what precisely will happen varies depending on whether the game is played face-to-face on a physical go board, or on an internet go server.

Face-to-face with a physical go board

During a face-to-face game, you can expect Black to play at the triangle before passing, and White will reply by playing at the square.

During face-to-face games with physical go board and stones, players typically fill all the dame, even when playing with Japanese rules, because it makes counting easier. Unfilled dame are extremely distracting when counting and can easily be mistaken for territory in the counting phase, when rearranging territories into rectangles. So players always fill dame.

However, when playing with Japanese rules, the dame-filling phase is sometimes played somewhat-separately from the "real" game. For instance, if the game is played with a clock, then players might pause the clock before filling the dame, and they might also fill the dame out of order. Since Black should not play the dame marked with a square before playing at the triangle, and since White would put Black in atari if White played the dame with the square before Black connected at the triangle, Black would probably still play the triangle during the game, before the dame-filling phase, just to avoid any ambituities. And then the players would pause the clock and fill the dame, including the square.

Online play

When playing online with Japanese rules, the players most often don't bother to play dame, because counting is done automatically by the computer, and territories are typically coloured, so neutral points are not too distracting nor confusing.

However, what happens around the triangle intersection will depend on the go server and the counting algorithm used by the go server.

For instance, the go server KGS correctly detects simple teire points like the triangle, when playing with Japanese rules. So, Black would not receive a point for the triangle intersection, even if it is unfilled. If both players know this, because they have played several games on KGS already and are familiar with, and confident in, the scoring algorithm used by the server, then it's very likely that Black will pass without connecting at the triangle. Likewise, White will pass without playing the atari at the square.

However, if playing on a go server that doesn't handle teire points as well as KGS, or if the players are not entirely sure how the go server handles teire points, or if one or both of the players are driven by the habits they got when playing face-to-face games, then it is very likely that Black will play at the triangle; and if Black doesn't play at the triangle first, then White will play the atari at the square, to force Black to connect at the triangle.

So, it's a big if. The triangle point will only remain unfilled if the server correctly detects teire points when playing with Japanese rules, and both players are familiar enough with the server, and not driven by their habits from face-to-face games.