Opening Rolls

 Opening 62: Split, run, or slot?

 From: Chuck Bower Address: bower@bigbang.astro.indiana.edu Date: 7 May 1997 Subject: Re: Opening roll of 6-2 Forum: rec.games.backgammon Google: 5kqp2m\$kt4\$1@dismay.ucs.indiana.edu

```Chuck Bower mentions:
> Starting the 5-point with 62 is on its last breath ... Slotting the
> bar-point (ala Becker)--pressurized oxygen isn't enough.

JCDill writes:
> Boy, am I *out* of it!
> What is the "popular" 6-2 move, if not to start the 5-point?  You run?
> You can be hit with a 4 either way, but if NOT hit the blot on the
> 5-point is far more valuable to building, why start a running game?

Here are the answers, but whether you believe them is another matter...

1) "Popular" among humans is 24/18, 13/11.

2) "You run?" being 24/16 is also under serious consideration, based on
rollouts by Jellyfish v2.01 (and other motivations as well).  13/5 is
still seen occasionally (by human players).  Yesterday my FIBS opp.
played 13/7, 13/11.  Could s/he have been the elusive Becker?????

Here are Jellyfish v2.01 level-6 cubeless rollout equities (for opener):

equity     standard deviation     statistical chances

24/16               +0.018          0.013                 85%
24/18, 13/11        -0.001          0.013                 15%
13/5                -0.034          0.014                 <0.1%

(NOTE:  "statistical chances" means that if all 3 candidates were rolled
out "an infinite number of times" (instead of the actual 504 times), this
is the probability that the given play would come out "best".)

I could have done more rollouts, but feel that is pointless.  JF
doesn't play "perfect" backgammon, so better statistical significance
will still leave systematic uncertainty.  I'd rather wait for JF v3.0
and use the computer cycles for something better in the meantime.

The argument "both 24/16 and 13/5 get hit by a 4" is unfortunately
only qualitative.  When hit, the 13/5 play is considerably worse, and
if missed, considerably better.  (The above argument glosses over the
considerably worse branch.)  If you let JF do the QUANTITATIVE analysis,
combining all 36 outcomes and weighting them accordingly, 13/5 comes
in a distant 3rd, as seen above.

Could 13/5 be the best play in the long run?  As always, it does
matter how you define "best".  But, if you are more specific and ask:

If supercomputerbackgammonplayer (the winner of the Backgammon
Championship of the Universe--open to humans AND robots) plays
itself a trillion games with each of the opening 62 plays, which
play comes out best?

My guess is that 13/5 will NOT work out best.  But it could.  Right now
it doesn't seem to be in favor by the robots or most of their more fickle
charcoal brained cousins.

Chuck
bower@bigbang.astro.indiana.edu
c_ray on FIBS
```

### Opening Rolls

At different match scores  (Louis Nardy Pillards, July 2002)
Average advantage of winning opening roll  (Chuck Bower, Oct 1998)
Choosing a strategy  (Daniel Murphy, June 2001)
Early game rule of thumb  (Rich Munitz, Feb 2009)
Factors to consider  (Kit Woolsey, July 1994)
How computers play  (Kit Woolsey, Mar 1995)
Magriel's Chapter 5  (Hayden Alfano+, May 2006)
Mloner vs Jellyfish  (Kit Woolsey, Dec 1995)
Nactating a whole game  (Nack Ballard+, Jan 2011)
Nactation  (Jim Stutz+, June 2010)
Nactation overview  (Nack Ballard, Oct 2009)
Nactation--Why use it?  (leobueno+, Jan 2011)
Opening 1's: Split or slot?  (Douglas Zare, Dec 2003)
Opening 21: Rollout  (Stick, Mar 2006)
Opening 21: Split or slot?  (Dick Adams+, Dec 2003)
Opening 32: Rollout  (Stick, Feb 2006)
Opening 43: In GOL online match  (Raccoon+, Feb 2004)
Opening 43: Pros and cons  (Stick+, Jan 2006)
Opening 43: Which split is better?  (Peter Backgren+, Aug 2000)
Opening 43: Which split is better?  (Michael J. Zehr+, Mar 1996)
Opening 51: Rollout  (Stick, Feb 2006)
Opening 52: Merits of splitting  (Peter Bell, Apr 1995)
Opening 53: Magriel's recommendation  (George Parker+, July 1997)
Opening 53: Split to 21?  (Alex Zamanian, Aug 2000)
Opening 53: Why make the three point?  (Kit Woolsey+, Feb 1996)
Opening 6's: Slot the bar point?  (Chuck Bower+, Feb 2000)
Opening 6's: Slot the bar point?  (David Montgomery, June 1995)
Opening 62: Could running be best?  (Gary Wong, Sept 1997)
Opening 62: Split, run, or slot?  (Chuck Bower, May 1997)
Opening 63: Middle Eastern split?  (Mark+, Apr 2002)
Opening 63: Slot the four point?  (Dennis Cartwright+, Mar 2002)
Opening 64: Make the two point?  (William Hill+, Jan 1998)
Opening 64: Make the two point?  (Darse Billings, Feb 1995)
Opening 64: Rollout  (Peter Grotrian, Jan 2006)
Opening 64: Split to 20?  (Peter Bell, June 1995)
Opening 64: Three choices  (Brian Sheppard, July 1997)
Opening 65: Becker on lover's leap  (Jeffrey Spiegler+, Aug 1991)
Opening 65: Computer rankings  (Chuck Bower, Jan 1997)
Opening rolls ranked  (Arthur+, Apr 2005)
Rollouts of opening 21 and replies  (Alexander Nitschke, Oct 1997)
Rollouts of openings  (Tom Keith+, Jan 2006)
Rollouts: Expert Backgammon  (Tom Fahland, Aug 1994)
Rollouts: Jellyfish 3.0  (Midas+, Sept 1997)
Rollouts: Jellyfish 3.0 level 6  (Chuck Bower, Feb 1999)
Rollouts: Snowie 4.1  (Rene Cerutti, Apr 2004)
Slotting the four point  (Joe Loria+, Oct 1999)
Snowie's openers and replies  (rcerutti, Feb 1999)
Splitting versus building  (Dave Slayton+, Aug 2000)
Splitting versus slotting  (Daniel Murphy, Apr 2001)
Splitting versus slotting  (Daniel Murphy, Sept 1997)
Trice's rankings  (Marty Storer, Feb 1992)