Concession stand, part 2

[Tim Chow]

XGID=-BBBBBB-----bA----bdBc-bb-:0:0:1:43:0:0:0:1:10

X:Player 1 O:Player 2
Score is X:0 O:0 1 pt(s) match.
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O | | O X O O O |
| O | | O X O O O |
| | | O O |
| | | O |
| | | |
| |BAR| |
| | | |
| | | |
| | | |
| O | | X X X X X X |
| O | | X X X X X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pipcount X: 95 O: 82 X-O: 0-0/1
Cube : 1
X to play 43

---
Tim Chow

[Bradley K. Sherman]

Tim Chow <tchow...@yahoo.com> wrote:
> +13-14-15-16-17-18------19-20-21-22-23-24-+
> | X O | | O X O O O |
> | O | | O X O O O |
> | | | O O |
> | | | O |
> | | | |
> | |BAR| |
> | | | |
> | | | |
> | | | |
> | O | | X X X X X X |
> | O | | X X X X X X |
> +12-11-10--9--8--7-------6--5--4--3--2--1-+

>Pipcount X: 95 O: 82 X-O: 0-0/1, Cube: 1, X to play 43

I'll play 13/6. X has excellent race chances.

--bks

[badgolferman]

13/6

[Walt]

Behind by 13 pips, I can't see playing 20/13.

So the choice is 13/7 or 6/2 6/3 or 5/2 5/1

At DMP I think I want to keep as much contact for as long as possible.
5/2 5/1 allows me to play 5s without having to break any more contact
and I can play 6s from the midpoint. 13/7 puts that checker out of play
and forces me to leave the anchor if I shake a 6.

5/2 5/1.



--
//Walt

[Bradley K. Sherman]

Walt <walt_...@yahoo.com> wrote:
>> +13-14-15-16-17-18------19-20-21-22-23-24-+
>> | X O | | O X O O O |
>> | O | | O X O O O |
>> | | | O O |
>> | | | O |
>> | | | |
>> | |BAR| |
>> | | | |
>> | | | |
>> | | | |
>> | O | | X X X X X X |
>> | O | | X X X X X X |
>> +12-11-10--9--8--7-------6--5--4--3--2--1-+

>> X to play 43
> ...
>5/2 5/1.

If that move is right, I'm giving up backgammon for 36 hours.

--bks

[Tim Chow]

When I posted a "concession stand" problem here last year, breaking
anchor turned out to be the bot's preferred play. At the time, I
issued the warning: "Don't try this at home."

http://groups.google.com/group/rec.games.backgammon/msg/676679531e0c5071

Unfortunately, I disregarded my own advice here, and played 20/13.
The advantage of 20/13 is that it keeps the pressure on O's midpoint.
An important source of X's equity is the potential for hitting a shot
on O's midpoint when she leaves a blot there. Playing 13/6 means that
X will probably get only an indirect shot at that blot. Playing 20/13
improves X's timing; next turn, X may even be able to run one checker
from the midpoint, keeping checkers on the 20pt and 13pt as sentinels.

The trouble with 20/13 is that it leaves X's straggler vulnerable to
attack. Though X does have the stronger board, O's blotless four-
point board, with no dead checkers, is nothing to sneeze at. 20/13
gives O too many rolls to attack X's blot with little or no risk.
It's too bold a play here. If O's board were weaker (see variant
below), 20/13 could be considered.

=======
Rollout
=======

1. Rollout: 13/6 eq:-0.285
Player : 35.76% (G:1.80% B:0.01%)
Opponent: 64.24% (G:1.73% B:0.01%)
Confidence: ±0.003 (-0.288<E<-0.282)

2. Rollout: 20/13 eq:-0.332 (-0.047)
Player : 33.42% (G:2.69% B:0.02%)
Opponent: 66.58% (G:4.17% B:0.02%)
Confidence: ±0.003 (-0.335<E<-0.329)

1296 Games rolled with Variance Reduction.
Dice Seed: 2
Moves and cube decisions: 3 ply

=======
Variant
=======

XGID=-BBBBBB-----bA----beBc-ba-:0:0:1:43:0:0:0:1:10

X:Player 1 O:Player 2
Score is X:0 O:0 1 pt(s) match.
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O | | O X O O O |
| O | | O X O O |
| | | O O |
| | | O |
| | | O |
| |BAR| |
| | | |
| | | |
| | | |
| O | | X X X X X X |
| O | | X X X X X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+

Pipcount X: 95 O: 87 X-O: 0-0/1

Cube : 1
X to play 43

1. Rollout: 13/6 eq:-0.206
Player : 39.68% (G:1.63% B:0.00%)
Opponent: 60.32% (G:2.42% B:0.01%)
Confidence: ±0.003 (-0.209<E<-0.203)

2. Rollout: 20/13 eq:-0.212 (-0.006)
Player : 39.39% (G:2.33% B:0.02%)
Opponent: 60.61% (G:2.70% B:0.01%)
Confidence: ±0.003 (-0.215<E<-0.209)

1296 Games rolled with Variance Reduction.
Dice Seed: 2
Moves and cube decisions: 3 ply

eXtreme Gammon Version: 1.21, MET: Rockwell-Kazaross

---
Tim Chow