Forum Archive : Terminology


From:   Raccoon
Date:   27 January 2007
Subject:   Re: German-American PRaTS ?
Forum:   GammOnLine

Paul Lamford popularized PRAT as an acronym for Position, Race and Threat
in his 2002 book Using PRAT as a guide, for instance, an advantage in all
three categories generally means Double/Pass or Too Good; in two categories
Double/Take or Double/Pass.

The quote:

> Das Rennen, Position und Drohungen Kriterium für Dopplungsentscheidungen.
> Mit diesen drei Kriterien (R-P-D) lässt sich die Stellung bemessen und
> bietet bei einem Vorteil in mindestens zwei Punkten eine ausreichende
> Überlegenheit zum Doppeln. Ein Vorteil in mindestens einem Kriterium
> rechtfertigt das Annehmen eines Dopplers.

is from an article in Harald Johanni's Backgammon magazin issue 2, April
1990, summarizing a seminar given at the 1989 European Championship in
Deauville by the 1988 World Cup winner Joe Sylvester.

Adam Tansley  writes:

Paul Lamford may have popularised PRAT, but I don't think he lays any claim
to inventing it. Fellow British player Robin Clay discussed it's use in his
1996 book Backgammon Winning Strategies. Interesting to hear it mentioned
earlier than that. Next time I see him, I'll ask Paul where he first acme
accross the idea.

David Montgomery  writes:

I remember what I think was a Joe Sylvester article in Flint of Chicago
Point from 80's or 90's on this. And I have a vague recollection that
Sylvester (or whoever) may have attributed the idea to something/someone

Raccoon  writes:

Kleinman reference to Sylvester in Flint:

"How can we tell when to turn the cube? How can we tell when to take it?

"These are the questions Joe Sylvester addresses in a recent issue of Flint
Backgammonews. To solve them, Joe proposes his 'CIA #2':

"Evaluate the race, positional features, and threats. An edge in two of
these three departments justifies a double or redouble. An edge in all
three makes it a pass."

-- Danny Kleinman, p.18 of But Only the Hogs Win Backgammons, 1991

"CIA" stands for "Concept In Action."

Kleinman, continuing, rejects "CIA #2" as an inadequate basis for both
double and take decisions, since these require quantitative, not
qualitative, estimates: "to establish that O should take we need
quantitative estimates: that (after adjusting for gammons and redoubling
potential) O has at least 25% chances. To show that X should double, we
likewise need quantitative estimates: that X is beyond O's pass-point, or
that X has threats (of such-and-such probability) to go beyond O's pass-
point (by so much) after each side rolls once."

Thus, that one side has "an edge" in three of three departments isn't
enough to tell us that the other side should pass; that one side has "an
edge" in two of three departments doesn't mean the position is a double, or
a take. It might be too good. It might be no double. It might be a take or
a pass.

Kleinman, continuing, writes "I can't for the life of me derive any
quantitative estimates from the qualitative analysis [showing that one side
has an edge in this or that department] of Positions 1 and 2, nor do I
think Joe or anyone else can." He suggests, however, two methods of
relating the features of a position to a quantitative estimate of win
probabilities: (1) by noting and when possible summing "mutually exclusive
ways of winning" -- by priming, blitzing, racing, hitting a late shot,
etc., since mutually exclusive ways of winning are cumulative, all adding
"positive probabilities, yielding a larger probability," and (2) by
comparing the position to "acquir[ed] benchmarks distinguishing passes from
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