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# Cube influence on moves - EXAMPLE PLEASE!

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### Bill Taylor

Jan 30, 1995, 9:43:20 PM1/30/95
to
This topic came up just recently as a sub-thread about the cube; it was one
I'd been meaning to inquire about for some time. Various people said there
were plenty of examples, but no-one has actually posted one!

At least I didn't see any. So could someone please put their money where
someone else's mouth is, and give an example.

That is: an example of a position and roll, where the roll would be better
played two different ways, depending on which side the cube's on.

I would hope for as clear-cut an example as possible; preferably an end-game
example, where the various expectations could be calculated exactly. But even
if that isn't possible, then at least an example for which there would be very
little difference of opinion among good players.

Thanks.
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Bill Taylor w...@math.canterbury.ac.nz
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God does not play dice with the universe, he plays Go.
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### Michael J Zehr

Jan 30, 1995, 11:44:57 PM1/30/95
to
In article <3gk848\$k...@cantua.canterbury.ac.nz> w...@math.canterbury.ac.nz (Bill Taylor) writes:
>This topic came up just recently as a sub-thread about the cube;
>That is: an example of a position and roll, where the roll would be better
> played two different ways, depending on which side the cube's on.

Well, according to Chuck Giallanza, writing in "Inside Backgammon"
(march-april 94), with the following position:

O: 8 0 0 0 0 0
vs.
X: 0 0 1 0 4 1

X on roll to play 64.
if X owns the cube or the cube is in the center, you play 6-2 5-0. If
the cube is dead or O has the cube, you play 6-0 5-1. The difference in
the two plays is pretty small.

O: 1 2 2 1
vs.
X: 0 3 0 0 0 1

X to play a 1.
If the cube is dead, X should play 2-1. Otherwise, X should play 6-5.
Here the difference in the plays is pretty big.

Finally:
O: 3 3
X: 0 1 2 0 0 2

X to play 41.
If X owns the cube or it's in the center, the best play is 6-2 3-2. If
O owns the cube or the cube is dead, the best play is 6-1.

To see why these positions work out like this, one would have to look
ahead at cube decisions on following rolls, something that I haven't
done yet.

It's much more common for checker plays to depend on the match score
rather than the cube position, but that's s different question.

-michael j zehr

### Kit Woolsey

Jan 30, 1995, 11:41:47 PM1/30/95
to
Bill Taylor (w...@math.canterbury.ac.nz) wrote:
: This topic came up just recently as a sub-thread about the cube; it was one

: I'd been meaning to inquire about for some time. Various people said there
: were plenty of examples, but no-one has actually posted one!

: At least I didn't see any. So could someone please put their money where
: someone else's mouth is, and give an example.

: That is: an example of a position and roll, where the roll would be better
: played two different ways, depending on which side the cube's on.

: I would hope for as clear-cut an example as possible; preferably an end-game
: example, where the various expectations could be calculated exactly. But even
: if that isn't possible, then at least an example for which there would be very
: little difference of opinion among good players.

Sure enough. Here's a simple example. Suppose you have a closed board
with spares on your 3, 7, and 8 points, and you opponent has one checker
on the bar and his other 14 checkers deep in his home board someplace.
You have chosen to play on for the gammon (and why not, since nothing bad
can happen next roll and if you roll an awkward number you can then
reconsider and cash if you think it proper to do so). Now you roll 5-5.
If you own the cube your proper play is 8/3, 7/2, 5/off(2). The reason
is that you are planning on doubling next turn, so you want to minimize
the effect of your opponent's best roll now! If you play "safe" by
moving two men from the 6 point and he rolls boxes, suddenly he has a
fighting chance in the race and can take a double. It doesn't matter
that by taking two men off you are risking leaving a shot next turn
because of the gap, because that shot will never come -- you will turn
the cube before you roll, and your opponent will be forced to pass.
However if he already owns the cube, then your proper play is 8/3, 7/2,
6/1(2). Now you will have to worry about leaving the shot next roll, and
the danger of that is greater than the danger of losing the race
outright. There are other possible examples, some much more complex, but
this one should be pretty clear.

Kit

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