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Three Point Anchor Games

Posted By: Albert Steg
Date: Wednesday, 6 July 2016, at 1:55 p.m.

I've been trying to work on mastering more reference positions and have run into a challenge understanding when I can take '3 Point Anchor' games. My starting place oaths one is Mochy's :"Three Point Anchor Games" Gibraltar lecture, which lays out the maximum pip count deficit one can accept in taking cubes holding that anchor. For instance, with the 7 & 9 points open, he finds that 22 pips is the borderline.

Checking out similar positions in Kit Woolsey's 'Backgammon Encyclopedia Vol 1', I found that position 3-2 is such a position, with a 30-pip deficit that is an easy take. Huh. So I went back to Mochy's lecture and saw that he offers a caveat that White's distribution of spares is actually more important than the pip count. See Slide #19 here:

http://www.slideshare.net/masayukimochizuki1/three-point-anchor-games

Hmmm . . . this is where I'm wishing I was a t the lecture because there must have been some explanation about what kinds of distributions count as awkward (is the distribution on that slide really "bad?" -- the difference is moving the spare open the mid to the 2-pt.) I've tried moving the Leader's checkers (Blue, below) around on Kit's position in various ways smoothing it out to get to a pass but find this is a pretty comfortable take regardless. For instance here's a small take with 26 pips deficit:

		White is Player 1 score: 0 pip: 134 Unlimited Game Jacoby Beaver pip: 108 score: 0 Blue is Player 2
XGID=---BBBBAA---cC---c-cccB---:0:0:-1:00:0:0:3:0:10
Blue on roll, cube action?

Analyzed in Rollout	No double	Double/Take
Player Winning Chances:	76.42% (G:4.56% B:0.08%)	76.49% (G:4.47% B:0.08%)
Opponent Winning Chances:	23.58% (G:1.71% B:0.04%)	23.51% (G:1.73% B:0.04%)
Cubeless Equities	+0.557	+1.115
Cubeful Equities
No double:	+0.935 (-0.054)	±0.009 (+0.926..+0.944)
Double/Take:	+0.989	±0.010 (+0.979..+0.998)
Double/Pass:	+1.000 (+0.011)
Best Cube action: Double / Take
Rollout details
1296 Games rolled with Variance Reduction. Moves: 3-ply, cube decisions: XG Roller
Double Decision confidence:		100.0%
Take Decision confidence:		98.9%
Duration: 2 minutes 52 seconds

eXtreme Gammon Version: 2.10

So, I find myself either not understanding the "distribution" issue, or doubting that looking at pip count deficits in these positions is really the right way to go. At the moment I'm sort of liking Kit's mention of an adage that "any 3-point game is at worst almost a take" -- just look for aggravating factors in either direction that put it on one side or the other?

Any insights / opinions into how to evaluate these positions appreciated (as are Kit's and Mochy's efforts to share their knowledge!)

Albert

Messages In This Thread

• Three Point Anchor Games
  Albert Steg -- Wednesday, 6 July 2016, at 1:55 p.m.
  • Three Point Anchor Games
    Casper Van der Tak -- Wednesday, 6 July 2016, at 2:03 p.m.
  • Three Point Anchor Games
    Igor -- Wednesday, 6 July 2016, at 2:56 p.m.
  • Three Point Anchor Games
    Joe Russell -- Thursday, 7 July 2016, at 3:22 a.m.
  • any 3-point game is at worst almost a take
    Mochy -- Thursday, 7 July 2016, at 5:35 a.m.
    • any 3-point game is at worst almost a take
      Casper Van der Tak -- Thursday, 7 July 2016, at 6:16 a.m.
    • any 3-point game is at worst almost a take
      Albert Steg -- Friday, 8 July 2016, at 2:20 p.m.
      • any 3-point game is at worst almost a take
        Mochy -- Friday, 8 July 2016, at 3:30 p.m.
      • any 3-point game is at worst almost a take
        Bob Koca -- Friday, 8 July 2016, at 4:40 p.m.
    • any 3-point game is at worst almost a take
      Seth -- Monday, 11 July 2016, at 2:57 a.m.
      • any 3-point game is at worst almost a take
        Bob Koca -- Monday, 11 July 2016, at 4:06 p.m.
        • any 3-point game is at worst almost a take
          Seth -- Tuesday, 12 July 2016, at 12:53 a.m.