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        Arimaa >> General Discussion >> Illegal move ?
        
(Message started by: pago on Oct 13^th, 2010, 8:45am)

Title: Illegal move ?
Post by pago on Oct 13^th, 2010, 8:45am

Hello,

During the game #141589 between Bot-Marwin and Arimabuff, the bot played the following move :
70w rb8s Ha8e Hb8e rb7n

I thought it was illegal because one shall play a move that changes the position.

Note that it changes nothing to the poor position of the poor bot...

Title: Re: Illegal move ?
Post by pago on Oct 13^th, 2010, 8:47am

Oups !!!

Sorry : I didn't see that the third step was east (not west)

don't act

Title: Re: Illegal move ?
Post by 722caasi on Oct 13^th, 2010, 6:42pm

I'm glad you could answer your question. However, it raises a larger point: Do bot move generation programs generate the move "pass" as a move? Which bots "play" it?

Title: Re: Illegal move ?
Post by rbarreira on Oct 14^th, 2010, 4:26am

on 10/13/10 at 18:42:06, 722caasi wrote:

I'm glad you could answer your question. However, it raises a larger point: Do bot move generation programs generate the move "pass" as a move? Which bots "play" it?

There are many moves which don't change the board (moving one piece back and forth, or doing that twice, or doing that with two pieces, and more...), so this needs to be treated in a general way. It's not enough to avoid the "pass" move.

My guess is that if the existing bots didn't avoid those moves, illegal moves would happen frequently enough that we would notice it. I personally have never seen any of those moves in the game logs.

Title: Re: Illegal move ?
Post by Sconibulus on Oct 14^th, 2010, 8:10am

I think he means pass, as in the move you select when you decide to play less than four steps.

As far as I know, all bots play this move, but often it requires getting them into a position of severe difficulty.

Also, in case I'm wrong, there are a handful of bots on the ladder, mostly older ones, that will submit an empty move if they can't find a move that would make their situation a whole lot worse.

Title: Re: Illegal move ?
Post by Fritzlein on Oct 14^th, 2010, 12:16pm

There are still some quirks, such as Bomb being able to pass only on the last step. I saw a game in which Bomb crashed because it needed to make a one-step move and couldn't. And jdb has demonstrated freaky endgames where being able to make a two-step move is the difference between losing and winning, not just the difference between crashing and losing gracefully.

Bomb2004 had to play all four steps, which caused frequent quirks in the endgame, but merely being allowed to pass the fourth step took care of most of the issue.

Title: Re: Illegal move ?
Post by 722caasi on Oct 14^th, 2010, 6:44pm

Speaking of illegal moves, Clueless2005 lost in this game (http://arimaa.com/arimaa/gameroom/opengamewin.cgi?client=1&gameid=157217&role=v&side=w)because it did not understand/implement the three time repetition rule.

Title: Re: Illegal move ?
Post by omar on Oct 15^th, 2010, 9:25am

The older bots didn't have the 3rd time repetition rule implemented. Also bots prior to 2008 don't know about the rabbit elimination rule. Eventually I would like to have only bots that function well on the beginner ladder.