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Do you hit? And if so, what's the 3?

Posted By: Timothy Chow
Date: Thursday, 11 February 2010, at 6:16 p.m.

In Response To: Do you hit? And if so, what's the 3? (Timothy Chow)

Failing to hit here is a whopper. White's board is nothing to be afraid of, and we are already far behind in the race. Importantly, White is almost totally escaped, so we cannot count on getting another shot.

Over the board, I played 13/12*/9, reasoning in much the same way as the other people who have posted here recommending that move. However, the GNU rollout indicates that this is a serious mistake. The way I am inclined to explain this is as follows. When one is trying to contain a single checker, it is even more important than usual to ensure that one's checkers are positioned with maximum efficiency, cooperating with each other effectively. In particular, rushing forward to attack and make points is not always the best strategy. One's checkers do not necessarily need to be at the front lines to be positioned well. It is more important to ensure that as many rolls as possible play well. With this attitude in mind, one sees that after 13/12*, the checker on the 12-point is not badly positioned, whereas the checker on the 24-point is out of play and can be made to serve a useful function if it is stepped up.

By the way, this position reminds me of Position 1 in Norm Wiggins's book Boards, Blots, and Double Shots, shown below. For a long time I couldn't understand why 24/18 was the preferred move. It looked unnatural to me to step up the back checker when behind in the race, instead of advancing 11/5 in preparation for attacking or building my board. But again I think the point is that our first priority is to contain White's back checker, and the Blue checker on the 11-point is actually well-positioned for that. It's Blue's rear checker that is out of play and that can be made into a useful asset if it is converted into a spare on the bar-point anchor.

Here is Wiggins's position:

gnubg	130
tchow	158
Position ID: 2M0xAxDMhuVgIA Match ID: cIkUAAAAAAAA

And here is the rollout of my original position:

gnubg	119
tchow	146
Position ID: sG9jCgAan8EAIw Match ID: UYkFAGAAEAAA

#		Ply	Move	Equity
•	1	R	24/21 13/12*	-0.332
			0.317 0.064 0.002 - 0.683 0.166 0.006 -0.473 -0.332 0.002 0.001 0.000 - 0.002 0.002 0.001 0.004 0.013
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 843349808 and quasi-random dice
			Play: supremo 2-ply cubeful prune [world class]
			keep the first 0 0-ply moves and up to 16 more moves within equity 0.32
			Skip pruning for 1-ply moves.
			Cube: 2-ply cubeful prune [world class]
	2	R	13/12*/9	-0.397 ( -0.066)
			0.306 0.068 0.002 - 0.694 0.188 0.010 -0.516 -0.397 0.002 0.001 0.000 - 0.002 0.002 0.001 0.004 0.006
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 843349808 and quasi-random dice
			Play: supremo 2-ply cubeful prune [world class]
			keep the first 0 0-ply moves and up to 16 more moves within equity 0.32
			Skip pruning for 1-ply moves.
			Cube: 2-ply cubeful prune [world class]
	3	R	13/12* 13/10	-0.440 ( -0.108)
			0.301 0.066 0.003 - 0.699 0.216 0.013 -0.558 -0.440 0.002 0.001 0.000 - 0.002 0.002 0.001 0.004 0.006
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 843349808 and quasi-random dice
			Play: supremo 2-ply cubeful prune [world class]
			keep the first 0 0-ply moves and up to 16 more moves within equity 0.32
			Skip pruning for 1-ply moves.
			Cube: 2-ply cubeful prune [world class]
	4	R	13/12* 6/3	-0.447 ( -0.115)
			0.292 0.064 0.002 - 0.708 0.204 0.011 -0.565 -0.447 0.002 0.001 0.000 - 0.002 0.002 0.001 0.004 0.006
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 843349808 and quasi-random dice
			Play: supremo 2-ply cubeful prune [world class]
			keep the first 0 0-ply moves and up to 16 more moves within equity 0.32
			Skip pruning for 1-ply moves.
			Cube: 2-ply cubeful prune [world class]
	5	R	8/5 6/5	-0.499 ( -0.167)
			0.246 0.037 0.001 - 0.754 0.114 0.005 -0.589 -0.499 0.001 0.001 0.000 - 0.001 0.002 0.000 0.003 0.005
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 843349808 and quasi-random dice
			Play: supremo 2-ply cubeful prune [world class]
			keep the first 0 0-ply moves and up to 16 more moves within equity 0.32
			Skip pruning for 1-ply moves.
			Cube: 2-ply cubeful prune [world class]

Messages In This Thread

• Do you hit? And if so, what's the 3?
  Timothy Chow -- Wednesday, 10 February 2010, at 8:38 p.m.
  • Do you hit? And if so, what's the 3?
    John O'Hagan -- Wednesday, 10 February 2010, at 9:18 p.m.
  • Do you hit? And if so, what's the 3?
    David -- Wednesday, 10 February 2010, at 9:21 p.m.
  • Do you hit? And if so, what's the 3?
    Rich Munitz -- Wednesday, 10 February 2010, at 9:54 p.m.
  • Do you hit? And if so, what's the 3?
    Seth -- Wednesday, 10 February 2010, at 10:24 p.m.
  • Do you hit? And if so, what's the 3?
    rummer1973 -- Wednesday, 10 February 2010, at 10:39 p.m.
  • Do you hit? And if so, what's the 3?
    Steve Mellen -- Wednesday, 10 February 2010, at 10:47 p.m.
  • Do you hit? And if so, what's the 3?
    Neil Robins -- Wednesday, 10 February 2010, at 10:53 p.m.
  • Do you hit? And if so, what's the 3?
    neilkaz -- Wednesday, 10 February 2010, at 11:18 p.m.
  • Do you hit? And if so, what's the 3?
    Nack Ballard -- Wednesday, 10 February 2010, at 11:58 p.m.
    • Do you hit? And if so, what's the 3?
      neilkaz -- Thursday, 11 February 2010, at 2:42 a.m.
  • Do you hit? And if so, what's the 3?
    Timothy Chow -- Thursday, 11 February 2010, at 6:16 p.m.
    • Do you hit? And if so, what's the 3?
      Steve Mellen -- Thursday, 11 February 2010, at 7:13 p.m.