Hi all,

I introduced backgammon to a friend of mine who has always wanted to learn to play.

Recently, he asked when does it become physically impossible to win ie you simply cannot roll the dice to get you over the line - so to speak.

I told him that only in bearing off when you are so behind that you simply cannot roll enough high numbers or doubles does this occur.

This is correct, yes?

Al Mirpuri

I believe you are correct, sir.

If your opponent beats off 14 checkers and then you hit his remaining checker, you will have some nonzero winning chance. Even if all of your checkers other than the one you hit with are piled on your ace point, your opponent could theoretically roll 11 repeatedly and dance while you bring that checker around and beat off your checkers. Therefore ANY position in which contact is not broken will have some winning chance for both players. Only non contact positions can be gin.

Note: being a no contact position is a necessary condition but not a sufficient one for a player to have zero win probability. Obviously there are plenty of no contact positions where both players have winning chances.

How about this for a gin position with contact?

Theoretically, white could still lose if he don't find the best play on some unlucky rolls :

white can roll 11 then play 4/2* 1/off(2) then black hit with a 2 which give him some very small winning chances

white can roll 21 then play 4/2* 1/off then get hit which give black some very small winning chances

white can also roll 21 then play 4/2* 2/1 then if black dance by rolling 11, white take 2 checkers off then black hit with a 1, then black have some winning chances even if pretty small. Also black have some chances of saving the gammon in this scenario, the position is not gin if a player have 100% winning chances but opponent still have to fight to save the gammon, play must go on to determine how much points the winner will get)

these scenarios can look ridiculous, but I think that some players would play 4/2* 2/1 in this position if they roll 21 (you know, some players really like to hit)

Also, if white bear off 11 checkers and have the remaining 4 checkers on his ace points and black have a checker on the bar, is this considered a contact position ? This is not a serious question, I am just messing around.

Anyway, the position is not gin because black have to fight to save the backgammon, so the play must go on.

I put the position on GNU and if white roll 21, 4/2* 2/1 is the best move even if you give black 1/1000 chance to win the game because it increase the backgammon chances. I can't believe I waste 1 hour of my life to figure this out. Backgammon is fun

100 % correct

Thank you all who responded.

Stremba70 for the win.

My 1-liner is still correct though.

Ok, imagine my position at DMP where White doesn’t need to take a risk to win a gammon or backgammon. That is a gin position (i.e., 100% wins) with contact (i.e., hitting is possible, and in fact the correct play for White is to hit with 11). This appears to be a counterexample to “ANY position in which contact is not broken will have some winning chance for both players. Only non contact positions can be gin.”

Of course if White plays incorrectly it’s possible to lose, but I think most wouldn’t consider the possibility of losing with incorrect play sufficient to make it a non-gin position.

@sdfsgf

Once White has played in your position, Black doesn't have "real" contact anymore. He either stays on the bar or enters in a non-contact position.

Technically, one could argue that you're right.
But logically, that's not what I would qualify as "real" contact.

“Technically correct” is all I wanted!

So, the title of the thread need to be change for ''When does it become technically impossible to win''