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Topic: Black Wins in Boat-Pente Wedge Opening? Rare instance found.
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zoeyk

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Registered: Mar 4, 2007
From: San Francisco
Age: 43
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Black Wins in Boat-Pente Wedge Opening? Rare instance found.
Posted: Nov 15, 2008, 9:28 AM

So there has been some talk on the tables I've heard.
Players theorizing that black might be able to force a win in Boat~Pente by using the "Wedge Opening".

A search for the "Holy Grail Opening" to crack the code of Boat~Pente,.. forever becoming a P2 victory.

While me and Up2ng attempted,..we stumbled onto a Rare instance.

No we didn't find the holy~grail opening,..but check the end of this..

Black has a Pente,..Black also has 5 Captures,..
But White Wins by Pente.





Scire hostis animum - Intelligere ludum - Nosce te ipsum - Prima moventur conciliat - Nolite errare


watsu

Posts: 1,270
Registered: Dec 16, 2001
Re: Black Wins in Boat-Pente Wedge Opening? Rare instance found.
Posted: Nov 16, 2008, 2:19 AM

Very cool. In ninuki that position would be a drawn game.

Retired from TB Pente, but still playing live games & exploring variants like D, poof and boat
up2ng

Posts: 542
Registered: May 9, 2002
From: Northeast USA
Re: Black Wins in Boat-Pente Wedge Opening? Rare instance found.
Posted: Nov 17, 2008, 5:24 AM

Yes, we made that very comment at the time that this would be a draw in ninuki (actually, we weren't sure what the exact rule was in ninuki, I know that if someone makes a 5th capture which creates a perfect 5 for your opponent, it's a draw -- in this case black makes a 5th capture AND a 5 -- although I guess it's not a perfect 5 -- but if it were, is this still a draw in ninuki? watsu knows the rules better than we do so I assume he's correct that this would be a draw).

Now, in Boat-Pente, a "perfect" overline also wins, so this was a situation where that final cap was forced because white had just made a pente, and as I understand the Boat-Pente rules, the pente has to be broken on the very next move (right?). However, we weren't exactly sure what would happen -- and we weren't exactly sure what SHOULD happen!

So, in this case, white made an unperfect pente, 6-in-a-row. At this point we half assumed the game would end, but it did not! Look at the board after white's 18th move. White actually does have 5 unbreakable stones in a row (G2 - L6) but it is part of an overline that has a capturable pair hanging off it. Should the game have continued? What is the Boat-Pente rule for this situation? Next, black captures accross this overline leaving white with (still) an unbreakable 5 and black with 5 captures AND a breakable 5. The win was awarded to white after this move -- was this correct? Are there ties in Boat-Pente or not? What if black had created an UNbreakable pente along with white's unbreakable pente with this move? Who wins then?

I'm not sure who the expert in Boat-Pente rules is around here but let's have someone who knows for sure weigh in on this and let us know what SHOULD have happened in this situation and if it turns out that it's different than what did happen, Dweebo should be made aware of this bug in the code.

zoeyk

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Re: Black Wins in Boat-Pente Wedge Opening? Rare instance found.
Posted: Nov 17, 2008, 10:01 AM

well,...my step dad Jay E. Hoff invented Boat~Pente over 25 years ago. So i suppose "he" should choose the answer to this,..I'll give him a call and ask him to read this and come to a decision on the matter.

at which point dweebo will need to update the Boat~Pente Rules in the F.A.Q. Game Rules section/
and possibly "re-code" the game's rules.



~zoeyk

Scire hostis animum - Intelligere ludum - Nosce te ipsum - Prima moventur conciliat - Nolite errare
watsu

Posts: 1,270
Registered: Dec 16, 2001
Re: Black Wins in Boat-Pente Wedge Opening? Rare instance found.
Posted: Nov 18, 2008, 2:56 AM

well, I haven't seen anything in the rules of ninuki which covers the making of a five in addition to the fifth pair capture while making a six into a five. In such ambiguous rule situations, I think we have to come up with codeable logic which seems to best reflect the situation...
As a heirarchy, I would propose the following for such situations in boat/ninuki.
Not fifth capture, but makes imperfect five and perfect five for opponent- loss
Fifth capture makes perfect five for opponent- draw
Fifth capture + imperfect five makes perfect five for opponent- draw
Fifth capture + perfect five makes perfect five for opponent- either win or draw- win would balance out the loss while making a five on the other end, but OTOH, winning with a five and a fifth capture still only wins the game once in terms of rating points, so should this count extra or not?

An alternate solution would be something like what we have in poof pente, where a move which simultaneously creates an equal winning position for both players doesn't end game play- play continues until one player or the other establishes a winning position.

It can be a hard decision to reach as to what makes the most sense in these ambiguous situations- my initial sense for poof pente was that the game should end as a draw, but after further consideration I decided against that. Anyway, it'll be interesting to find out how it turns out for Boat. As for ninuki, I doubt there's an official rulekeeper for that game, so we'll have to decide by consensus, I suppose, for cases such as the three listed above which I haven't found covered in ninuki rules and also one which I noticed recently- if a capture from a six creates an imperfect five, does the capturer lose to that five or have a turn after the opponent plays in order to potentially capture across the imperfect 5?

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

Posts: 141
Registered: Feb 29, 2004
From: the land of smelly cheese
Age: 38
Re: Black Wins in Boat-Pente Wedge Opening? Rare instance found.
Posted: Nov 18, 2008, 6:23 AM

Looking at it, to me it's obvious that the game should have ended when the white made an unbreakable 5-in-a-row.

The fact that it was an overline that could be broken is immaterial and a bug in the code IMHO, because even though the overline was breakable, it did not break the pente, and to me the boat rules are clear - if you can make an unbreakable pente you win.

up2ng

Posts: 542
Registered: May 9, 2002
From: Northeast USA
Re: Black Wins in Boat-Pente Wedge Opening? Rare instance found.
Posted: Nov 18, 2008, 6:31 AM

lepews I agree with you and that's what I thought also -- and I also thought that what happened in this case might be a bug.

Remember this differs from ninuki rules which always ignore an overline (overlines do not win, unlike in Boat Pente in which overlines do win -- unless your opponent can capture on the next move to break up the Pente).

zoeyk

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From: San Francisco
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Re: Black Wins in Boat-Pente Wedge Opening? Rare instance found.
Posted: Nov 18, 2008, 8:36 AM

well youll notice that although you call it a bug,...that the code did declare white the winner,..so perhaps not a bug after all,...of course in a perfect code the game would had ended without giving black a final move,.. but it was un-needed to code since it did not alter the logical ending,...that is if this is to be the rule of course....i havnt talked to Jay to get his opinion on the matter yet. i have a feeling he'll have the same out look on it, but i dunno.

Scire hostis animum - Intelligere ludum - Nosce te ipsum - Prima moventur conciliat - Nolite errare
dweebo

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Re: Black Wins in Boat-Pente Wedge Opening? Rare instance found.
Posted: Nov 18, 2008, 8:24 PM

very interesting occurrence there, good find you guys!

i think i agree with lepews that it should be a win as soon as black is unable to break up the 5, and that my code isn't handling that case correctly. but whatever you guys decide, we can update the rules and modify the code to do whatever.

-dweebo

Pente Rocks!
watsu

Posts: 1,270
Registered: Dec 16, 2001
Re: Black Wins in Boat-Pente Wedge Opening? Rare instance found.
Posted: Nov 19, 2008, 4:02 AM

White actually makes two fives, one "breakable" and one not. If both fives were either breakable or unbreakable there would be no ambiguity, but since only one is breakable we have a situation where the coding as it stands interprets the position as a breakble one even though one five will remain unbreakable after a capture. Is this really a bad thing, provided that white is given the win after black's move no matter whether black makes 2 winning overlines and captures for a total of 14 stones (or whatever) with that move. Technically, the game should perhaps have been over as soon as a single five was created which couldn't be broken, but the way I always mentally visualize positions such as this is the way that the code has apparently been set up which seems to be as follows. Player x makes move. Opponent responds. Evaluate board after opponent's response. Is there a five created by player x on the board? If yes, then player x wins. If no, then it is player x's turn to move. This scenario has the advantage of covering the situation where player x creates a "breakable" five but his/her opponent fails to break it on their next turn, and the only potential disadvantage is that there is one further move allowed after the win "occurs" than there would be the other way...

Retired from TB Pente, but still playing live games & exploring variants like D, poof and boat
up2ng

Posts: 542
Registered: May 9, 2002
From: Northeast USA
Re: Black Wins in Boat-Pente Wedge Opening? Rare instance found.
Posted: Nov 19, 2008, 5:29 AM

Remember that although black made a 5 with the final move, it was a breakable 5 -- we don't know for sure what would have happened if an unbreakable 5 were created, but I have a feeling that white would have still been awarded the win.

I don't think the code does exactly what you are thinking here watsu because normally when a player makes an unbreakable 5 the game ends right away. It is more likely that the code checks for a Pente (5 or more in a row) and if it is unbreakable, end the game and (white) wins, but if it is breakable, set some kind of status that remembers who might win if this Pente is not immediately broken. Then, after the opponent's next move and before checking for the opponent's Pente (as was done above), check for a Pente -- if there is one then end the game and (white) wins.

It seems that the code does not correctly determine if an overline is breakable -- which would be a bug.

Again, it's interesting that this would be unnecessary in games like Ninuki, where overlines do not win -- and in fact different logic would have to be put in place to check for an opponent's Pente after a capture.

dweebo

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Age: 37
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Re: Black Wins in Boat-Pente Wedge Opening? Rare instance found.
Posted: Nov 19, 2008, 11:13 PM

I had a heck of a time getting the code to work correctly for boat-pente as I'm sure zoey can tell you, we went back and forth a few times before I figured it out.

up2ng has it right on how the algorithm works, except i don't "set some kind of status that remembers", i just check again.

The actual algorithm is sort of hard to express in english but here is how I did it.

  1. scan the board and find all instances of lines with 5+ stones for both players.
  2. for each 5+ line found:

    1. if the line is for the player who didn't just move, then that player wins. return from the algorithm.
    2. otherwise check if any captures can be made across the line. if no captures are possible across the line then set the winner to be the player that just moved and continue checking the rest of the 5+ lines.

  3. after all 5+ lines checked, if we found a winner from step 2b above, that player wins. return from the algorithm.
  4. otherwise see if either player has captures 10 stones, and if so set the winner and return.


So I think the code is doing the right thing overall, since there is no way for the player breaking the overline to win IF after breaking it there still remains a 5+ line. The only improvement that could be made would be to detect in step 2b that the possible capture actually disrupts the Pente to make the game one move shorter.

-dweebo

Pente Rocks!
jayehoff

Posts: 2
Registered: Mar 5, 2007
From: Sausalito
Age: 62
Re: Black Wins in Boat-Pente Wedge Opening? Rare instance found.
Posted: Nov 22, 2008, 10:38 PM

White wins, black did not cap from the pente. Six is allowed.

Replies: 12   Views: 24,515   Pages: 1  
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