A Sweet (and miraculous) Backgammon Win

 

 

I'm red in the above diagram, moving clockwise, and it's my roll. My online opponent, Dorothea, has already borne off 8 of her 15 checkers. I've made no points in my inner board, have a man on the bar, and I'm facing a certain gammon (and a possible backgammon) with the doubling cube already at 2. This was the first game of a 3 point match and even just a gammon would give her the match. Would you believe I came back to win from this position? Here's a copy of the full game in a text format. If you have the popular Jellyfish backgammon program, download this text file and then rename it by giving it a GAM rather than a TXT extension. Then run Jellyfish and simply open this file to replay the whole game. (Otherwise, you'll probably need your own backgammon set and will have to replay the game over by hand to enjoy my victory.) Note: the win is very instructive.

 

Additional note: I just evaluated the above position with the very strong Monte Carlo backgammon program. (This program is available online to evaluate positions. The URL is http://www.gamercafe.com/monte/eval/ )

This is what it gives for the above position:

Dorothea's chances of winning the game: 99.2%
Dorothea's chances winning a gammon: 93.9%
Dorothea's chances of winning a backgammon: 47.6%

My chances of winning the game: .8%
My chances of winning a gammon or a backgammon are 0%

Obviously I have a "zero" chance for a gammon or a backgammon myself, since Dorothea has already borne off some checkers. The most I can hope for is to simply win the game, which I did! According to the above mentioned Monte Carlo backgammon program, I had just a .8 chance of winning from this position! Incredible!

I also recently posted this position in rec.games.backgammon and asked others who have strong backgammon programs to evaluate it. I received two replies:

1) Snowie says you had a 3.1% chance of winning.  X's equity is 1.838.  The chance of a backgammon is 47.9% and the chance of at least a gammon is 88.4%

2) Jellyfish Level 7 says your game-winning chances are 8.7%.  Presumably you are going to clear the ace-point to leave a blot to force him to play 2-1 with an ace after he clears the 3.  But he has 20 rolls that leave a blot next turn anyway and you will hit 1/3 of the time roughly, so you are 1/6 to hit next turn. Of course of the 91% of the games you lose, 30% are gammons and 43% are backgammons!

Okay, so my chances were apparently better than .8%. Obviously though, they are apparently less than 8.7% and possibly closer to 3.1%.

 

If I have any more miraculous wins I'll post them here too.

 

 

I do have another miraculous win!  Here it is!

Here, I'm again red and again playing online against an opponent by the handle of "bambino." In the above position, it's bambino's move. From this position, Monte Carlo gives bambino a...

98.8% chance of winning the game
61.1% chance of winning a gammon
3% chance of winning a backgammon

However, bambino here rolled a 5-1 and although he correctly took off two more checkers, he was forced to leave a blot on his three-point. I then rolled a 1-1 and hit it.

I moved my back man around and began taking off checkers and was fortunate enough to be able to take off ten men (!) before bambino rolled a 5-2 in the position below and was finally able to leave the bar. The resulting race was then rather close but I managed to win.

Here's a copy of this game in a text format. Again, if you have the popular Jellyfish backgammon program, download this text file and then rename it by giving it a GAM rather than a TXT extension. Then run Jellyfish and simply open this file to replay the whole game.