[Bug-gnubg] Odd rollout results of classic reference position

[ershaw]

Five off and one closed out is traditioanlly a take. A GnuBg rollout has it
as a pass. I've got no problem with that.

What is odd is that the equit of No DOuble is greater than 1. How can this
be? That would make it Too Good in a position where no gammons are possible.

This is yet another position where the doubler is seen to win more games by
doubling than by holding on to the cube. I would expect O to double X out in
some games if O has cube access. Therefore X ought to win less games if he
gives up the cube. Something seems wrong. Is it me?

--Ian

    GNU Backgammon  Position ID: tw0AANp2dwAAAA
                    Match ID   : UQkAAAAAAAAA
    +24-23-22-21-20-19------18-17-16-15-14-13-+  O: gnubg
  O | O  O  O  O       | O |                  |  0 points
  O | O  O  O  O       |   |                  |
  O | O                |   |                  |
  O |                  |   |                  |
  O |                  |   |                  |
    |                  |BAR|                  |v
    |                  |   |                  |
    |                  |   |                  |
    |          X  X  X |   |                  |
    | X  X  X  X  X  X |   |                  |  On roll
    | X  X  X  X  X  X |   |                  |  0 points
    +-1--2--3--4--5--6-------7--8--9-10-11-12-+  X: user (Cube: 2)

Cube analysis
Rollout cubeless equity  +0.584

Cubeful equities:
1. Double, pass         +1.000
2. Double, take         +1.061  ( +0.048)
3. No double            +1.013  ( +0.000)
Proper cube action: Redouble, pass
Rollout details:
Player user owns 2-cube:
  0.792 0.000 0.000 - 0.208 0.000 0.000 CL  +0.584 CF  +1.013
 [0.000 0.000 0.000 - 0.000 0.000 0.000 CL   0.001 CF  +0.003]
Player gnubg owns 4-cube:
  0.795 0.000 0.000 - 0.205 0.000 0.000 CL  +1.181 CF  +1.061
 [0.001 0.000 0.000 - 0.001 0.000 0.000 CL   0.002 CF  +0.003]
Full cubeful rollout with var.redn.
1296 games, seed 1206724736 using quasi-random dice and Mersenne Twister
Play and cube: 2-ply cubeful 100% speed [world class]