Newsletter for 23 March 2004

Spring is here...

On Tuesday, 23 March 2004, the Backgammon Club of San Diego met, and not so surprisingly, a tournament erupted.

Tournament News

Seven people entered a 16-player bracket on Tuesday night. We had the following tournament results:

Current Master Points Standings

Bruce has moved to within eight points of the top spot, still held by Jason Lee. Osman, by splitting for the win with Bruce has moved into 4th place overall, while Tom moves into a 5th place tie with Sho Sengoku. 
 1. Jason Lee        39
 2. Bruce Haight     31
 3. Adrian Costa     25
 4. Osman Guner      13
 5. Tom Fahland      12
 6. Sho Sengoku      12
 7. Cyrus Mobedshahi 10
 8. Marcia Karen      9
 9. Eric Sedehi       8
10. Fred Kamgar       5
11. Greg Kopp         2
12. Maira Costa       1
13. Sam Mehri         1
The point leader at the end of the year will be named the BCSD Player of the Year, and the top 16 in the Master Point standings will be invited to the 2004 BCSD Tournament of Champions, to be held in early 2005.

News from Chicago

Congratulations to the BCSD's own Sho Sengoku, who took first place in a Midwest Championship special event -- Pyramid Gammon. For his efforts, Sho took home a Taki-Egyptian backgammon set. Way to go, Sho!!!

Problem of the Week

+-13-14-15-16-17-18-+---+-19-20-21-22-23-24-+
|dX1X ' ' ' ' ' ' ' ' ' '|
|   |
|      |  56  |
|1X3O2O2O2O3O|   |2O '1O ' ' '|
+-12-11-10--9--8--7-+---+--6--5--4--3--2--1-+

Money game. Pip counts: White 39, Black 71
Position ID: /18AACBu200AAA Match ID: QYkaAAAAAAAA

There are two reasonable plays here. There's the obvious -- close out the last checker with 7/1 6/1, but there's another type of play not to be missed: 9/3 6/1. The goal is to try to recycle a checker in an attempt to hit the extra White blot, thereby increasing winning or gammon chances. Is it worth it?

Last Week's Problem of the Week

A problem given by Sho Sengoku -- can you come up with an example of a position in a money game where you have only an 18.75% chance of winning the game, no chance of a gammon, and yet you can take a double?

Here's the holy grail of a position:

+-13-14-15-16-17-18-+---+-19-20-21-22-23-24-+
| ' ' ' ' '1X ' ' ' ' ' '|
|   |
|      |      |
| ' ' ' ' '1O|   | ' ' ' ' ' '|
+-12-11-10--9--8--7-+---+--6--5--4--3--2--1-+

Money game. Pip counts: White 6, Black 6
Position ID: IAAAgAAAAAAAAA Match ID: cAkAAAAAAAAA

• Black doubles

Cube decision
2-ply cubeless equity +0.625 
 0.813 0.000 0.000 - 0.188 0.000 0.000
Cubeful equities:
1.Double, pass +1.000 
2.Double, take +1.000 +0.000
3.No double +0.500 -0.500
Proper cube action:Double, pass

GNU says PASS is correct, but actually, you'll notice that the equity is the same for take and pass, so this is actually OPTIONAL for White.

What's going on here? Why can White take with only 18.75% winning chances? Interestingly enough, the reason is that if White takes, and Black fails to bear off, White has a perfectly efficient cube. What that means is that White's double would then be an optional take/pass for Black! The backgammon players who understand the cube the best know that the cube to fear the most is the EFFICIENT cube -- a cube where the take/pass decision is borderline. When you cube efficiently, you are unlocking the most power out of the cube.

Because White has such an efficient recube (and will always have one, if the game progresses to that point), White can take with much lower equity that usual. Without gammons present, this is the lowest possible takepoint in money play, although it's not known if other examples exist with this property -- it's unlikely that any do.

The other side of the coin is, of course, when you cube efficiently, your opponent cannot make a huge mistake, by definition. Inefficient cubes offer your opponent the chance to err. What a double edged sword!

See you next week! Keep tossing those cubes,
J. Lee

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