Opening Rolls

Forum Archive : Opening Rolls

Opening 52: Merits of splitting

From:   Peter Bell
Date:   4 April 1995
Subject:   Opening 5-2: 24/22, 13/8 ??
Google:   3lspoo$

Hi all,

A couple of weeks ago, Kit Woolsey posted the following, summarizing the
results of opening moves experiments using computer backgammon programs:

"5-2: The normal play for years has been 13/11, 13/8.  However the newer
splitting play, 24/22, 13/8, (shunned because of the crushing 5-5 threat)
has come out a bit better.  The slotting play of 13/8, 6/4 (which used to
be my choice) did not survive the rollouts -- it was clearly inferior."

I'm no expert, but the possibility of 24/22 13/8 being better than 13/11,
13/8 baffles me.  5-5 is only 1/36, and it's only really crushing when
it's followed by a dance, 1/4 of the time -- total parlay, 1/144.
Therefore, I've been thinking about the other merits of 24/22 13/8:

1.) Building rolls: The best building rolls available to the back checkers
after the split are 3-1, 4-2, and 6-4.  However, these are all excellent
rolls anyway after 13/11 13/8.  3-1 makes the 5-pt, 4-2 the 4-pt, and 6-4
the bar point.  Furthermore, both 3-1 and 4-2 (and 6-4, for Jellyfish
fans!) leave the player who split with a choice between good alternatives.
 Why duplicate good rolls?

2.) Other rolls containing a 2: These make the 22-pt after the split,
which is nice, but not nearly as nice as the 21-pt or 20-pt.  It seems
that pursuing the 22-pt would be more important after the opponent has
built a decent prime.  Note that by making the 22-pt, the player reduces
the chance of later making the 21-pt or the 20-pt.  Meanwhile, after 13/11
13/8, a 2 makes the 11-pt.  It may not be as important as the 3-pt, but
it's nice to have, since it's 6 away from the 5-pt.  Therefore, it helps
both in offense - making the 5-pt - and in defense - fighting an opponent
who's made the 5-pt.

3.) All other rolls: the only other roll that seems like it might be
better after the split is 5-4, which escapes a back checker to the 13-pt.

4.) Other potential advantages of a split: discourage opponent's outfield
development; opponent gains nothing from hitting loose on the 22-pt

Overall, the only explanation that makes sense to me is that the computer
programs place more value on a good defense than a good offense.  Is
anyone familiar with how they play 3-1 or 4-2 after the split?  What about
early 2-2 or 3-3: do they move the defensive anchor forward or attack?
Can anyone figure out any other reasons why the split might be good?


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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)  [Recommended reading]
Magriel's Chapter 5  (Hayden Alfano+, May 2006)  [Long message]
Mloner vs Jellyfish  (Kit Woolsey, Dec 1995) 
Nactating a whole game  (Nack Ballard+, Jan 2011)  [Long message]
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)  [GammOnLine forum]
Opening 21: Split or slot?  (Dick Adams+, Dec 2003) 
Opening 32: Rollout  (Stick, Feb 2006)  [GammOnLine forum]
Opening 43: In GOL online match  (Raccoon+, Feb 2004)  [GammOnLine forum]
Opening 43: Pros and cons  (Stick+, Jan 2006)  [GammOnLine forum]
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)  [GammOnLine forum]
Opening 52: Merits of splitting  (Peter Bell, Apr 1995) 
Opening 53: Magriel's recommendation  (George Parker+, July 1997)  [Long message]
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)  [GammOnLine forum]
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)  [Recommended reading]
Rollouts: Snowie 4.1  (Rene Cerutti, Apr 2004) 
Slotting the four point  (Joe Loria+, Oct 1999) 
Snowie's openers and replies  (rcerutti, Feb 1999)  [Long message]
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) 

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