Playing in 21x21 or bigger

[Sano]

I was just wondering if anyone here has tried to play on boards bigger than 19x19. Is it fundamentally different than playing in a normal-sized board? Is it more complicated or simply somewhat different?

Edit: also, did anyone tried to play in a rectangular board (say, 19x21)? How do you think the gameplay would be affected?

[topazg]

37x37 is crazy! Apart from that, not really tried

[palapiku]

Getting territory (edge-facing stuff) becomes less valuable, getting influence (center-facing stuff) becomes more valuable, then everything follows from that.

[flOvermind]

I'm not so sure. I recall reading somewhere that the common pro opinion about 21x21 is that it emphasizes corners more and sides less. The reasoning behind that is that it's much easier to invade and much harder to attack the invasion because there is more space. If you use "normal" 19x19 joseki, you can basically first take the corners, giving away influence, and then invade the side without much problems...

I don't remember what the conclusion was about center facing influence, though.

[topazg]

I found on 37x37 the only thing you could be sure of was corner sequences. Edges were easier to claim than anything towards the middle. The center was an armageddon zone. Influence facing the center from the side wasn't that useful, it was just all a bit of a mess.

[Bill Spight]

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Click Here To Show Diagram Code

[go]$$B 21x21 Sanrensei
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The 21x21 is wide enough that sanrensei leaves room for the opponent to invade and make a two space extension. As people have pointed out, that makes a moyo game more difficult.

Every New Year's the Nihon Kiin has a 21x21 rengo. It would be interesting to see some of those games.

[hyperpape]

Another argument is that on 9 x 9 and smaller boards, opening on tengen is obviously a very good move. It may well be the best (if this is true on 19x19, we have little reason to believe it).

The argument is rather limited, but what it does show is that the importance of center influence does not monotonically increase with the size of the board.

[Monadology]

$$B 21x21 Sanrensei
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Click Here To Show Diagram Code

[go]$$B 21x21 Sanrensei
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The 21x21 is wide enough that sanrensei leaves room for the opponent to invade and make a two space extension. As people have pointed out, that makes a moyo game more difficult.

Every New Year's the Nihon Kiin has a 21x21 rengo. It would be interesting to see some of those games.

Except that since the corners and edges are worth comparatively less, it may be that the appropriate response to the invasion is different on a 21x21 board. For instance, preventing the extension but letting him live in the corner may be worth more.

EDIT: Further, for all we know making an invasion like that and giving black sente with only a nirensei opening with white might be a poor choice of play. White's side is even more open than usual, and his two point extension has done less overall damage than it would on a 19x19 board.

[hyperpape]

For all you and I know, maybe. But it's much harder to be true for all Bill knows, and his informants may know even more than he does.

[Bill Spight]

Further, for all we know making an invasion like that and giving black sente with only a nirensei opening with white might be a poor choice of play. White's side is even more open than usual, and his two point extension has done less overall damage than it would on a 19x19 board.

I was not advocating that invasion, just pointing out the extra space.

[Monadology]

Further, for all we know making an invasion like that and giving black sente with only a nirensei opening with white might be a poor choice of play. White's side is even more open than usual, and his two point extension has done less overall damage than it would on a 19x19 board.

I was not advocating that invasion, just pointing out the extra space.

I was just pointing out that I don't think it follows that the Moyo game is necessarily more difficult because there is extra space to invade, something which you did say. It might be that the extra space only makes it more difficult if you give a particular response which is standard on a 19x19 board (e.g. the kick and extend). Especially with Moyo play, I think it is rather unlikely that standard play on a 19x19 board would remain optimal on a larger board. Any analysis would have to be much more thorough and start, to some degree, from scratch.

[Solomon]

I was just wondering if anyone here has tried to play on boards bigger than 19x19.

If you're beerslayer, 37x37 is standard.

[schilds]

I played beerslayer once on a 37x37.


I have nothing to substantiate it, but I think go strategy is somewhat fractal on larger boards. Roughly speaking, if a single stone is a fence post for a small group, then small groups are fence posts for larger groups and so on.

[flOvermind]

Except that since the corners and edges are worth comparatively less, ...

Why do you think that's the case? I'm pretty sure it's the other way round, that corners are worth more in comparison to outward facing influence.

Why should e.g. a 3-3 invasion be worth less on a bigger board? It still makes exactly the same amount of territory. But the resulting outward influence is (supposedly) worth less, because it's easier to invade the bigger space.

[schilds]

Eh, I don't buy either story.

It's the same wall, it projects the same strength outwards. The only thing to question is the value of that projected strength relative to the points gained in the corner. If we simply ask ourselves how we would approach to or extend from that wall, isn't the answer the same, regardless of board size? Would you really play any closer just because the board is bigger? Assuming your answer is 'no', then you're really saying that the wall is doing the same amount of work relative to the points in the corner, whatever the board size (well, unless it's on a really small board where its influence is truncated).

That's not to say I would discount any effect of increasing board size, just that I doubt it'd be so straightforward. If I were to guess, I'd guess at cycles or oscillations. e.g. on boards just the right size such that the game ends just after the 3-3 invasion sequence (because there's no room for the invading player to play again on the other side of the wall), then I would expect the wall to become more effective with increasing board size up until the point where it becomes possible to play and live on the other side. Then it might drop dramatically and increase again up until the point where a stone claiming the other corner also happens to be the right amount to extend from the wall. Perhaps the oscillations would become smaller the larger the board size. Or to put it another way, on small boards tactical considerations might swamp any of our nice generalized go theories (i.e. those theories break down at a small scale), with those same tactical considerations having relatively less effect as board size increases, and no reason for them to have any kind of linear effect. Not that I'm pretending to have a clue, just that if I were to pick a story to believe (going on no evidence), I'd pick that kind of story .