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# Edward Thorpe on running games?

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### Charles Blair

Sep 9, 1991, 5:39:28 PM9/9/91
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I saw a book by Phillip Martyn on a trip to England in 1978. I
didn't buy the book (to my later regret) but recall it mentioned a
technical paper by Edward (Beat the Dealer) Thorpe on running games.
Does anybody have a copy of this? I would also be interested in
mathematical analyses by other people.

### Simon Woodhead - Technical Consultant

Sep 10, 1991, 8:39:58 PM9/10/91
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Edward Thorpe worked out a formula for calculating race doubles
(an elaborated pip-count) which is claimed to be 99% accurate. There
are certain positions (described in Bill Robertie's "Advanced Backgammon")
where it falls down a little. On the whole, it is extremely accurate
for medium and long races, and has the advantage of being easily (:-)
calculated over the table.

This is the formula:

. Compute the leader's doubling number as follows:

2) plus two for each of the leader's remaining checkers,
3) plus one for each checker on the ace point,
4) minus one for each point covered in the home board,
5) plus 10% of the total so far, if that total is greater
than 30.

. Compute the trailer's doubling number by following steps
1-4, but omitting step 5. Call this result T, the trailer's

. If T > L-2, the leader should double.
. If T > L-1, the leader should redouble.
. If T > L+2, the trailer should pass.

Looks harder than it is. Anyone serious should be able to do a
normal pip count fairly quickly. Adding/subtracting the other bits
just takes a bit of practise.

If you want something a little easier, try this:

. Compute both player's pip count. Find the difference and
compare that difference to the leader's count.

. With a difference of 8% or more, the leader has an initial double.
. With a difference of 9% or more, the leader has a redouble.
. With a difference of 12% or less, the trailer has a take.

Note that these formulae apply to money-game races, and do not take
any account of match-play scores. Use at your own risk!

Cheers,

Simon si...@Aus.Sun.COM

COM
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