Priming cube, sort of

[Tim Chow]

XGID=---bBBBCBA-----b---bbCcbb-:0:0:1:00:0:0:0:0:10

X:Player 2 O:Player 1
Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| O | | O O X O O O |
| O | | O O X O O O |
| | | X O |
| | | |
| | | |
| |BAR| |
| | | |
| | | |
| X | | |
| X X | | X X X O |
| X X X | | X X X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 139 O: 101 X-O: 0-0
Cube: 1
X on roll, cube action

---
Tim Chow

[Paul]

ND/T X is very far from doubling here.
The pip count is a big problem for X who is far behind.

5 primes are strong though, so X is a clear favourite.
X needs an immediate threat to double, and even then,
it's unlikely to be a clear pass.
Before doubling, X should be aiming at a blot or threatening
to make the full prime.
So a good exchange for X might well lead to a D/T.
I see very few market losers. I'm not sure there even is one.
If O crunches with an immediate 55, then O's enhanced pip count
can be a factor when X finally bears in and allows O's checkers to
escape.
Knowing that Tim's quizzes tend to have an instructional flavour,
I'm thinking that the trick is that none of the 441 sequences
are market losers, and Tim is waiting to excoriate us for doubling
in such an unnecessary way.

Paul

[Paul]

Actually, 44 seems like a market loser regardless of O's reply.
Not exactly a great reason to double, though.

Paul

[BlueDice]

On Sunday, October 29, 2017 at 6:57:25 PM UTC, Tim Chow wrote:

D/T
After I decided that this was a small D/T I read Paul's post and agree, not enough market losers to make it a double. I would still double against a much stronger player though.
--
BD

[Michael]

It looks to me it's a ND. For a start we have a race deficit, and what about market losers I don't see anything. Our 6s play bad (actually are blocked on both sides of the board). There might be spome market losers on 2nd exchange but why not just wait to see them before doubling.

ND/T

[Tim Chow]

Priming positions often reverse some rules of thumb. Usually, in backgammon,
one wants to be ahead in the race, but in a priming game you may want to be
behind in the race. Also, usually in backgammon, a "threat" is something
good that you might do, whereas in a priming battle, a threat may be something
bad that your opponent is about to do (i.e., crash). In the present position,
X isn't threatening to do anything particularly good, but O is threatening to
do something bad. She already has a dead checker and is on the verge of
deteriorating further. The rollout indicates that it's only a borderline
double, largely because X is at some risk of crashing himself. In the variant,
I have given X plenty of timing to the point where it's a borderline pass.

Analyzed in Rollout
No double
Player Winning Chances: 67.26% (G:16.26% B:0.55%)
Opponent Winning Chances: 32.74% (G:7.57% B:0.10%)
Double/Take
Player Winning Chances: 67.75% (G:16.84% B:0.61%)
Opponent Winning Chances: 32.25% (G:7.52% B:0.10%)

Cubeful Equities:
No double: +0.676 (-0.006)
Double/Take: +0.681
Double/Pass: +1.000 (+0.319)

Best Cube action: Double / Take

Rollout:
1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller
Confidence No Double: ± 0.011 (+0.665..+0.686)
Confidence Double: ± 0.017 (+0.664..+0.698)

eXtreme Gammon Version: 2.19.208.pre-release

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

XGID=---bBBBBB----B-b---bbCcbb-:0:0:1:00:0:0:0:0:10

X:Player 2 O:Player 1
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 O O O |
| X O | | O O X O O O |

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

Pip count X: 149 O: 101 X-O: 0-0

Cube: 1
X on roll, cube action

Analyzed in Rollout
No double
Player Winning Chances: 72.21% (G:17.14% B:0.60%)
Opponent Winning Chances: 27.79% (G:6.41% B:0.06%)
Double/Take
Player Winning Chances: 73.23% (G:17.98% B:0.69%)
Opponent Winning Chances: 26.77% (G:6.55% B:0.05%)

Cubeful Equities:
No double: +0.818 (-0.176)
Double/Take: +0.993
Double/Pass: +1.000 (+0.007)

Best Cube action: Double / Take

Rollout:
1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller
Confidence No Double: ± 0.009 (+0.808..+0.827)
Confidence Double: ± 0.017 (+0.976..+1.010)

eXtreme Gammon Version: 2.19.208.pre-release

---
Tim Chow

[Michael]

I only regret saying "I don't see many market losers".
The truth is there are plenty.
Not sure I could spot the right answer considering this is a volatile position, but I would at least have done a better effort.

Great positions for my SLP study.
Just increased my data from 36 to 38 ;-)