Make a second anchor?

[Timothy Chow]

XGID=-----aE-Ba--dD---d-e-BA--A:0:0:1:52:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O | | O X X |
| X O | | O X |
| X O | | O |
| X O | | O |
| | X | O |
| |BAR| |
| | | X |
| O | | X |
| O | | X |
| O X | | X |
| O O X | | X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 187 O: 150 X-O: 0-0
Cube: 1
X to play 52

---
Tim Chow

[ah....Clem]

Not enough timing for a backgame, and 54 backgames are not exactly the
best. Meanwhile, O has a bunch of stacked points plus two blots and no
board. I'll play bar/23 13/8 to unstack, put a spare on the 8, spread
checkers around to catch a blot (O is stacked so probably won't be able
to clean up the blots), and hang back to maintain contact.

Making a second anchor doesn't look bad though.

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

[Stick Rice]

If you're not going to make the 20pt anchor I suspect 6/4 is better than 13/8 as it's our heaviest stack.

Stick

[Timothy Chow]

A well-known general principle is that if you're far behind in the pip
count then you typically want to stay back for more contact. The idea
is to increase your chances of getting and hitting a shot, in order to
turn the tables. That reasoning might suggest bar/23 13/8 (staying
back as much as possible) or bar/20 6/4 (starting to build our board).
However, XG thinks both of those plays are in whopper territory compared
to making the second anchor. Why?

I think the reason is that making the second anchor already gives X
plenty of contact, and it puts a stop to several of O's joker rolls
that unload his stacks on X's blots (if X doesn't anchor up). In the
variant, I have moved X's existing anchor forward 3 pips, reducing
contact. The rollout still favors anchoring up, but by a much
narrower margin. The 5pt anchor and bar point anchor do not work
well together.

1. Rollout¹ Bar/20 22/20 eq:-0.306
Player: 42.06% (G:9.37% B:0.30%)
Opponent: 57.94% (G:11.53% B:0.37%)
Confidence: ±0.015 (-0.321..-0.291) - [100.0%]

2. Rollout¹ Bar/23 13/8 eq:-0.410 (-0.104)
Player: 40.09% (G:9.54% B:0.35%)
Opponent: 59.91% (G:16.33% B:0.63%)
Confidence: ±0.018 (-0.428..-0.392) - [0.0%]

3. Rollout¹ Bar/20 6/4 eq:-0.412 (-0.106)
Player: 40.61% (G:9.40% B:0.34%)
Opponent: 59.39% (G:16.81% B:0.65%)
Confidence: ±0.017 (-0.428..-0.395) - [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=-----aE-Ba--dD---dBe--A--A:0:0:1:52:0:0:0:0:10

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

| X O X | | O X |
| X O X | | O |

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

Pip count X: 181 O: 150 X-O: 0-0

Cube: 1
X to play 52

1. Rollout¹ Bar/20 22/20 eq:-0.346
Player: 40.18% (G:8.16% B:0.26%)
Opponent: 59.82% (G:9.71% B:0.28%)
Confidence: ±0.010 (-0.356..-0.337) - [99.4%]

2. Rollout¹ Bar/23 13/8 eq:-0.365 (-0.018)
Player: 41.41% (G:9.82% B:0.31%)
Opponent: 58.59% (G:16.45% B:0.69%)
Confidence: ±0.010 (-0.375..-0.354) - [0.6%]

¹ 2592 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