Hi Adi,
Gnubg doubling decisions are based on Rick Janowksi's theory, which I
don't think any human would want to replicate over the board.
Gnubg does not use the epc or any other adjusted pip-count method, which
are intended for humans. These are included purely for humans to use as
a study aid.
The best information I have on epc is in Walter Trice's Backgammon Boot
Camp, which is derived from his articles at Gammon Village. There are
further articles at GV by Trice and by Douglas Zare that expand on the
information found in Boot Camp. Thanks for the link to Joachim's paper,
which I'll enjoy reading. I haven't read it yet, so I can't tell whether
it adds new information, or summarizes what is already known - a
valuable thing in itself.
Trice explains that there is no general formula applicable to all
situations. This is because the epc only tells you the average rolls to
bear off, but not the amount of variance. If one player is stacked, a 65
is about as good as a 21, so there is less variance involved. This
effect tends to help the leader, because the trailer is relying on the
variance swings to catch up in the race. This means that for equal epc
races, the trailer is better off in "pips vs. pips" races". So. although
there is no universal formula, there are different rules that can be
applied depending on whether the nature of the race is "pips vs. pips",
"pips vs.. rolls" or "rolls vs. rolls".
Note to developers:
It might be a nice touch if Trice's formulae were added to the gnubg
race theory tab. It could possibly replace the 8-9-12 rule, which
applies in similar situations but is less accurate.
-- Ian
________________________________
From: bug-gnubg-bounces+ian.shaw=riverauto.co...@gnu.org
[mailto:bug-gnubg-bounces+ian.shaw=riverauto.co...@gnu.org] On Behalf Of
Adi Kadmon
Sent: 04 February 2011 13:45
To: bug-gnubg@gnu.org
Subject: [Bug-gnubg] Fwd: An important link and a question about
using EPC values in deciding cube actions
Oops sorry I forgot to put the link in the last delivery. It's
http://home.arcor.de/joachimmatussek/BearoffGWC.zip
- Adi
---------- Forwarded message ----------
From: Adi Kadmon <adi.kad...@gmail.com>
Date: Fri, Feb 4, 2011 at 3:42 PM
Subject: An important link and a question about using EPC values
in deciding cube actions
To: bug-gnubg@gnu.org
Hello all,
(1) As a sequel to a correspondence some months ago, here is a
link for downloading Joachim Matussek's important article about an
approximation-formula for EPC values and their use in cube decisions in
bearoff positions. This time it's the original article, and in English -
not just some section about it in a later article by someone else and
moreover in the Danish language.
http://home.arcor.de/joachimmatussek/BearoffGWC.zip
(2) I'd like to ask if there is at present a general formula for
deciding cube decisions in bearoff positions after the correct EPC
values are already given. I mean, does GNU make some particular
computation on the EPC values it extracts using its data-bases? For
instance, let's say Black has a raw pip count of 57 and EPC=65.41, and
White has a raw pip count of 60 pips and EPC=70.55, and it's White's
roll. Does GNU use a certain "formula" with these figures in order to
reach its evaluation of the correct cube decision? If so, does GNU use
the same formula in any position whatsoever, or is a different variant
of a formula needed for each different type of positions?
Anyway, even if GNU does not use such formula(s), what are
the current most modern approximation formulas (given already the exact
EPC values) for humans to use?
Thanks,
-- Adi
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