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Topic: Differences between board sizes
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t0afer

Posts: 47
Registered: Jan 7, 2021
Age: 30
Differences between board sizes
Posted: Oct 15, 2022, 7:45 PM

Does anyone have much experience with the 13x13 sized board for pente. The 19x19 size board seems extremely excessive given that the average game length is about 15 and so only involves a max of 30 stones.

That's only 8% of the board being used on average. Renju and Gomoku currently use a 15x15 sized board as a first player advantage mitigation (it turns some percentage of first player wins into draws), which doesn't really apply to pente since draws are rarer than blue moons.

I've played a few 15x15 games and it didn't seem to change much. Edge play might come up more often, but I didn't really notice.

Just wondering given my experience with the two if a 13x13 board is more reasonable a size for the game rather than borrowing Go's board.


watsu

Posts: 1,442
Registered: Dec 16, 2001
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Re: Differences between board sizes
Posted: Oct 15, 2022, 8:31 PM

13x13 boards change some standard pro openings. 15x15 might possibly change a few pro games, but would likely not have an effect on swap2.
ETA: theoretically, there may be one or more board size + variant which offers the possibility for a draw proposal with best play by both sides, but unless someone takes it on as a deep learning/supercomputer project, I doubt we'll be likely to stumble on it (them) by chance.


Message was edited by: watsu at Oct 15, 2022, 10:25 PM


Retired from TB Pente, but still playing live games & exploring variants like D, poof and boat
karlw

Posts: 968
Registered: Mar 7, 2006
From: Eugene, Oregon
Age: 32
Re: Differences between board sizes
Posted: Oct 16, 2022, 8:26 AM

In my recollection, having a 19x19 board is quite important in games that begin K10 O9 O10 (or N10). That transposition essentially moves the center of the board 4 (or 3) squares over.

watsu

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Re: Differences between board sizes
Posted: Oct 16, 2022, 5:09 PM

@ Karlw - yes, several first black moves on the 9 line often transpose the center at least 3 moves towards the edge of the board. Those include O9, N9 and M9. While it generally doesn't mean that white no longer has a winning second move, this does change standard 19x19 choices for lines.

Retired from TB Pente, but still playing live games & exploring variants like D, poof and boat
metzgerism

Posts: 17
Registered: Dec 5, 2021
From: Knoxville, TN
Re: Differences between board sizes
Posted: Oct 22, 2022, 8:08 PM

I've been trying to play as much 13x13 O-Pente as I can on BGA...as you probably remember, I was most interested in trying it on 11x11 and (after quite a few games of 9x9 and 13x13) I still feel that way. The border is a safe zone from capture, and with Keryo rules it extends a little closer to center - that's a very interesting dynamic.

watsu

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Registered: Dec 16, 2001
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Re: Differences between board sizes
Posted: Oct 23, 2022, 12:44 AM

O Pente as implemented on BGA is slightly different, since there's a built in draw situation from self captures (poof) at BGA. It's quite possible that swap2 13x13 BGA O Pente could be a drawn game with perfect play by both sides, though whether the edges or the 15-15 score would be more likely to yield drawn games I have no clue.

Retired from TB Pente, but still playing live games & exploring variants like D, poof and boat
watsu

Posts: 1,442
Registered: Dec 16, 2001
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Re: Differences between board sizes
Posted: Oct 26, 2022, 5:22 AM

What if an "ideal" board size turns out not to be an odd number, but rather an even number? 12x12 instead of 11x11 or 13x13? By "ideal" I mean something along the lines of optimally interesting and fair for both players. Let's say, for example that on an 11x11 board with swap2 opening rules the proposer has 50 possible proposals for a Pente variant which lead to a drawn game with best play by both sides. In half of those 50 proposals, the second player has multiple choices for moves at many points in the game. By contrast, if the board size is 12x12, let's say there may be only 3 distinct possible proposals which end in a draw if both sides play optimally and there are only single lines of optimal moves which result in a draw in those proposals. On a 13x13 board, one side or the other always has a win with optimal play, regardless of the initial proposal. In this hypothetical scenario, I would say that a 12x12 board size offers the most interesting and challenging game. The game Chek-ro has a 14x14 board size, I believe, with the first move being made on one of the 4 central points on the board. In swap2 proposals where the pieces can be placed anywhere on the board, having a single central point is obviously unnecessary, but Chek-ro illustrates that even with a first move in the center of the board beginning even numbered sides for board sizes are still workable.

Retired from TB Pente, but still playing live games & exploring variants like D, poof and boat
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