5pt or anchor?

[Timothy Chow]

XGID=-b----E-CA--dD---c-ccA--A-:0:0:1:31:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O | | O O X X |
| X O | | O O |
| X O | | O O |
| X | | |
| | | |
| |BAR| |
| | | X |
| O | | X |
| O X | | X |
| O X | | X O |
| O X X | | X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 160 O: 157 X-O: 0-0
Cube: 1
X to play 31

---
Tim Chow

[ah...Clem]

I don't see that anchoring is clearly superior to making the five point.
Maybe if there were more than nine in the zone...

And since I'm not sure anchoring is better, I'll make the five point.

[Timothy Chow]

There's an early-game heuristic that I learned from Nack Ballard:
either 5pt beats either 4pt. (You may find Stick's version more
memorable: either the 5pt or the 20pt beats either the 4pt or the
21pt.) Here, that would suggest making the 5pt rather than anchoring
on the 4pt. However, XG says that this position is an exception.
O's offensive position has developed enough that defending against
her threat to make her 4pt has increased significantly in value.
One way to think about it is that if X plays 8/5 6/5 and then O
points on X's head and X dances, then O will probably double. That's
quite a few bad sequences for X, whereas after 24/21 9/8, I'm having
a hard time seeing any sequences after which O would double.

In the variant, there are fewer ways for O to make her 4pt, and XG
thinks the decision is closer, but still wants to anchor.

1. Rollout¹ 24/21 9/8 eq:-0.107
Player: 46.98% (G:10.18% B:0.31%)
Opponent: 53.02% (G:10.08% B:0.38%)
Confidence: ±0.013 (-0.120..-0.094) - [100.0%]

2. Rollout¹ 8/5 6/5 eq:-0.189 (-0.082)
Player: 46.03% (G:13.63% B:0.80%)
Opponent: 53.97% (G:19.06% B:0.93%)
Confidence: ±0.017 (-0.205..-0.172) - [0.0%]

3. Rollout¹ 24/21 6/5 eq:-0.211 (-0.105)
Player: 44.87% (G:10.46% B:0.33%)
Opponent: 55.13% (G:13.26% B:0.49%)
Confidence: ±0.015 (-0.226..-0.196) - [0.0%]

¹ 1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.19.211.pre-release

-------
Variant
-------

XGID=-b----E-CA--dD---c-dbA--A-:0:0:1:31:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O | | O O X X |
| X O | | O O |
| X O | | O |

| X | | O |

| | | |
| |BAR| |
| | | X |
| O | | X |
| O X | | X |
| O X | | X O |
| O X X | | X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+

Pip count X: 160 O: 158 X-O: 0-0

Cube: 1
X to play 31

1. Rollout¹ 24/21 9/8 eq:-0.083
Player: 47.25% (G:10.17% B:0.29%)
Opponent: 52.75% (G:9.74% B:0.39%)
Confidence: ±0.006 (-0.090..-0.077) - [100.0%]

2. Rollout¹ 8/5 6/5 eq:-0.113 (-0.029)
Player: 47.72% (G:14.39% B:0.76%)
Opponent: 52.28% (G:17.40% B:0.89%)
Confidence: ±0.008 (-0.121..-0.104) - [0.0%]

¹ 5184 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.19.211.pre-release

---
Tim Chow

[Bradley K. Sherman]

Timothy Chow <tchow...@yahoo.com> wrote:
> ...

>There's an early-game heuristic that I learned from Nack Ballard:
>either 5pt beats either 4pt.

> ...

That makes sense. Any heuristics for 4pt vs. 7pt?

--bks

[Timothy Chow]

I don't know of any succinct ones. I think that the 4pt/7pt question
was going to be addressed by Paul Magriel in an upcoming book in the
Ballard/Weaver series of books on backgammon openings, but I fear that
the book will never see the light of day.

---
Tim Chow

[ah....Clem]

My hurestic is:


Make offensive or defensive 5 point before offensive or defensive 4 or
bar point.


Don't remember where I got it from, but it seems to work. Most of the
time anyway.

As for 4 vs bar point, the four point is more valuable than the bar
point once your opponent is off the ace point. Once they are, the bar
point doesn't block sixes and it's probably better to have another
homeboard point.

--
Ah....Clem
The future is fun, the future is fair.