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Stick's wild play rolled out at GS

Posted By: Daniel Murphy
Date: Thursday, 22 April 2010, at 4:19 p.m.

In Response To: Stick's wild play rolled out at GS (Timothy Chow)

Tim, thanks for the rollout at the altered score -2,-4 of the Stick/Stephen position originally posted by Paul at http://www.bgonline.org/forums/webbbs_config.pl?read=64338.

One note, though -- you wrote: The cubeless backgammon rate is not entirely negligible either for this position.

But at 2-away 4-away with the cube on 2, Leader and Trailer's backgammons are irrelevant (as are Leader's gammon wins). The rollout statistics for those three outcomes are best ignored, since Gnubg plays at-the-score and does not play to save irrelevant G's and BG's.

Here is a rollout at the original -1, -6 score:

The score (after 0 games) is: Stephan 9, Stick 14 (match to 15 points, post-Crawford play)

Move number 5: Stick to play 31

Stephan	88
Stick	83
Position ID: bdsKAQLP5hkAQA Match ID: UYnlAZAAcAAA

• Stick moves bar/24* 8/5*

Alert: lucky roll! ( +0.399)

#		Ply	Move	Equity
•	1	R	bar/24* 8/5*	-0.3664
			0.4491 0.3722 0.0559 - 0.5509 0.1917 0.0138 -0.3664 0.0016 0.0060 0.0041 - 0.0016 0.0021 0.0007 0.0049
			Full cubeless rollout (trunc. at one-sided bearoff) with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 854537717 and quasi-random dice
			Play: 2-ply cubeless prune
			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
	2	R	bar/24* 6/3	-0.4170 ( -0.0507)
			0.3581 0.2503 0.0235 - 0.6419 0.1050 0.0040 -0.4170 0.0015 0.0047 0.0028 - 0.0015 0.0021 0.0004 0.0037
			Full cubeless rollout (trunc. at one-sided bearoff) with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 854537717 and quasi-random dice
			Play: 2-ply cubeless prune
			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

It's odd that Gnubg reports 5.6% backgammon wins for the Leader in one rollout and 2.8% in the other, but in both rollouts they are meaningless statistics. I believe that the difference between the Leader's 1.4% relevant gammon losses at -1,-6 and 2.0% irrelevant gammon losses at -2,-4 are explained by Gnubg's not caring whether Leader loses a backgammon at -2,-4.

Messages In This Thread

• Stick's wild play rolled out at GS
  Timothy Chow -- Tuesday, 20 April 2010, at 10:28 p.m.
  • Stick's wild play rolled out at GS
    Daniel Murphy -- Thursday, 22 April 2010, at 4:19 p.m.
    • Stick's wild play rolled out at GS
      Timothy Chow -- Thursday, 22 April 2010, at 4:39 p.m.