BGonline.org Forums

backgame double

Posted By: Daniel Murphy
Date: Sunday, 25 October 2009, at 12:02 a.m.

In Response To: backgame double (aoleg1)

Gnubg doesn't seem to handle the original position well. It has something do, I think, with misevaluating the value of the three points in White's homeboard.

Suppose you don't double and roll 5-4 bar/20 8/4. Opponent fans. Now what? Double? Gnubg 2-ply says Double/Pass, with Take a 0.0801 blunder. But a short rollout says ND/T with Double a 0.141 blunder, and Pass a 0.045 error.

Since there must be quite a few similar sequences arising from the original position, we can conclude (if 2-ply isn't terribly misplaying either side) that in the original position, doubling is worse than what 2-ply says, but passing is also worse.

Unfortunately, a 2-ply rollout of the original position won't be much help, if that rollout has an inflated ND equity due to a lot of bad passes on the next roll.

And rolling out 5-4 ... dance (below) isn't much help either, since the ND equity is probably still inflated with bad passes next roll.

The score (after 0 games) is: Opponent 5, Hero 6 (match to 9 points)

Move number 8: Hero on roll, cube decision?

Opponent	171
Hero	119
Position ID: 22CAYUxxzpkBAg Match ID: cAkgAVAAMAAA

• Hero doubles

Alert: wrong double ( -0.1412)!

Cube decision
Rollout cubeless equity		+0.7494	(Money: +0.7021)
Cubeful equities:
1.	No double	+0.9550
2.	Double, pass	+1.0000	+0.0450
3.	Double, take	+0.8138	-0.1412
Proper cube action:		No double, take (75.9%)
Rollout details
Win W g W bg Lose L g L bg Cubeless Cubeful Centered 1-cube 0.7048 0.3093 0.0479 - 0.2952 0.0640 0.0007 +0.7494 +0.9550 Standard error 0.0049 0.0062 0.0131 - 0.0049 0.0123 0.0001 0.0177 0.0375 Player Opponent owns 2-cube 0.6761 0.3593 0.0657 - 0.3239 0.0877 0.0011 +1.6006 +0.8138 Standard error 0.0069 0.0133 0.0143 - 0.0069 0.0171 0.0003 0.0451 0.0689
Full cubeful rollout with var.redn.
144 games, Mersenne Twister dice gen. with seed 868991306 and quasi-random dice
Play: world class 2-ply cubeful prune [world class]
keep the first 0 0-ply moves and up to 8 more moves within equity 0.16
Skip pruning for 1-ply moves.
Cube: 2-ply cubeful prune [world class]

Annotation

Cube analysis
2-ply cubeless equity +0.8637 (Money: +0.6642)
0.7115 0.2885 0.0063 - 0.2885 0.0532 0.0004
Cubeful equities:
1. Double, pass +1.0000
2. Double, take +1.0801 ( +0.0801)
3. No double +0.9543 ( -0.0457)
Proper cube action: Double, pass

Messages In This Thread

• backgame double
  aoleg1 -- Friday, 23 October 2009, at 11:58 a.m.
  • backgame double
    Rich Munitz -- Friday, 23 October 2009, at 5:35 p.m.
    • backgame double
      Rich Munitz -- Friday, 23 October 2009, at 6:08 p.m.
  • backgame double
    neilkaz -- Friday, 23 October 2009, at 5:43 p.m.
  • backgame double
    aoleg1 -- Saturday, 24 October 2009, at 3:04 p.m.
    • backgame double
      Daniel Murphy -- Saturday, 24 October 2009, at 9:58 p.m.
    • backgame double
      Daniel Murphy -- Sunday, 25 October 2009, at 12:02 a.m.