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        Arimaa >> General Discussion >> Repetition rule
        
(Message started by: Swynndla on Mar 19th, 2006, 5:02pm)
Title: Repetition rule
Post by Swynndla on Mar 19th, 2006, 5:02pm
I know that if the same position appears three times in a game then the player who moved to make the position appear the third time loses (unlike in chess where it's a draw).

I also know that the repetition doesn't have to be consecutive, so if the position appears three times anywhere in the game then the repetition rule applies.

My question is, what if the same position appears as before, but some of the rabbits have swapped with each other, is that counted as a different position?
Title: Re: Repetition rule
Post by Ryan_Cable on Mar 19th, 2006, 5:23pm
Pieces of the same type and color are indistinguishable, so the positions would be identical and would count as a repetition.  If you try to swap a pair of pieces of the same type in a single move (which would require all 4 steps), the server will tell you that the move is illegal because it doesn’t change the position.  You can test these things out using the plan window; though for some strange reason it checks 4-fold repetition rather than the 3-fold repetition that is checked in actual games.
Title: Re: Repetition rule
Post by Swynndla on Apr 20th, 2006, 8:04pm
Does that position count only if it appears when a turn (eg 4 steps) has finished? ... or if it appears as one of the steps in that turn, does that could too?
Title: Re: Repetition rule
Post by Fritzlein on Apr 20th, 2006, 8:21pm
Only positions at the end of a turn are counted.  For the purposes of the repetition rule, the positions at the end of intermediate steps are irrelevant.
Title: Re: Repetition rule
Post by Swynndla on Apr 20th, 2006, 8:25pm
Thanks for clarifying this :)
Title: Re: Repetition rule
Post by omar on May 14th, 2006, 1:28pm
This is probably a better place to continue the discussion of the repitition rule that started under the topic "Fairy pieces".

http://arimaa.com/arimaa/forum/cgi/YaBB.cgi?board=talk;action=display;num=1144695637
Title: Re: Repetition rule
Post by omar on May 14th, 2006, 1:57pm
I think Brian makes a good case for why we should look for the 3rd repetition instead of the 2nd.

So a player should not be allowed to make a move that brings the board back to a previous position with the same side to move if it has already occured twice.

When playing online, such a repetition can be checked by the client software (and the server) and the move would not be allowed. The player can be given a warning on the 2nd repeat, but allowed to make the move. The move would not be allowed for the 3rd repeat; the player must simply make a different move. In the rare case that the player does not have any other move then the player loses by immobilization.

However when playing OTB the burden of checking for repeats lies on the opponent. If the 3rd (or greater) repeat is noticed by the opponent then the opponent can require the player to take back the move and make a different move.
Title: Re: Repetition rule
Post by unic on May 14th, 2006, 2:20pm
How will the various bots deal with this?  My impression is that many of them don't check repetitions, and thus will submit what will now be an illegal move.  (... and for Fairy, I can add it - but how about the various 2004 / 5 / 6 versions of bots?)
Title: Re: Repetition rule
Post by Fritzlein on May 14th, 2006, 6:58pm

on 05/14/06 at 14:20:13, unic wrote:
How will the various bots deal with this?

If I'm not mistaken, what Omar is proposing will have no effect on bots that check for repetition themselves, while bots that used to lose on repetition will now lose on time instead as the server awaits a different move that never arrives.
Title: Re: Repetition rule
Post by aaaa on May 23rd, 2007, 7:21am
Is the rule change still going to be made from lose to illegality? I can add a few additional arguments in favor of it:
  • It would be congruent with the fact that passing is also banned outright instead of causing an immediate lose.
  • It would give bot developers the (lazy) option of foregoing a repetition check in lieu of making the bot simply fall back to a backup move whenever the server reports the previous one was illegal.
  • Virtually every game that ends as a result of three-fold-repetition is effectively the result of a one-move blunder (akin to pushing an enemy rabbit to its goal row). Whenever this would not be the case and the move was in fact forced then we would like this to be explicitly made known. I would argue in favor of generalizing the term "immobilized" that is displayed by the game interface to something like "no legal move left" as the former is a possibly misleading categorization of such a situation.
Title: Re: Repetition rule
Post by NIC1138 on Jun 1st, 2007, 9:22pm
I'm sorry, but I  too lazy to check if this is aleady written somewhere ;D

...The repetition means the same STONE, or an equivalent stone in the same place?... In other word, dos it matters what horse wa where, or just that it was one horse?...
Title: Re: Repetition rule
Post by arimaa_master on Jun 2nd, 2007, 1:14am

on 06/01/07 at 21:22:45, NIC1138 wrote:
I'm sorry, but I  too lazy to check if this is aleady written somewhere ;D

...The repetition means the same STONE, or an equivalent stone in the same place?... In other word, dos it matters what horse wa where, or just that it was one horse?...



The equivalent stone in the same place - what matters is only the position (so you can swap any horse or dog or cat or rabbits as you will as far as the position is undistinguishable)
Title: Re: Repetition rule
Post by NIC1138 on Jun 2nd, 2007, 6:42pm

on 06/02/07 at 01:14:46, arimaa_master wrote:
The equivalent stone in the same place - what matters is only the position (so you can swap any horse or dog or cat or rabbits as you will as far as the position is undistinguishable)

Right then... But if you think about it, it's not that easy to swap rabbits!... Only your opponent can halp you to swap your rabits! 8)
Title: Re: Repetition rule
Post by RonWeasley on Jun 2nd, 2007, 9:53pm
Rabbit tricks are for muggles only.   Any wizard caught doing magic with rabbits gets laughed right out of Hogwarts.  Oh the humiliation.
Title: Re: Repetition rule
Post by aaaa on Jun 6th, 2007, 6:57am

on 06/02/07 at 01:14:46, arimaa_master wrote:
The equivalent stone in the same place - what matters is only the position (so you can swap any horse or dog or cat or rabbits as you will as far as the position is undistinguishable)


This is a good thing as it would make things significantly harder for the bot developers and could penalize bot performance.


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