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Stick's sword revisited

Posted By: Timothy Chow
Date: Wednesday, 17 February 2010, at 2:49 a.m.

Not long ago, Stick posted a position at 5-away/11-away with double 1's to play. The double 1's could be used to make the 4-point, or to make 5 out of 6 consecutive points, or to block the 6-away point. Stick wrote:

You will get into situations like this one where the other options are appealing, even damn appealing. They seem to accomplish many things at once and you will talk yourself into some other play. Don't do it, make the 4pt!

Intrigued, I played around with the position a bit. The most interesting result, in my opinion, was the rollout below. The score has been changed to gammon go. In the original position that Stick posted, making the 4-point only narrowly edged ahead of the second play, 22/21 10/9(3), which was the play I preferred. One might guess that at GG, making the 4-point would be hugely right. GG means that it's a no-brainer to make a home-board point, right? Well, surprisingly, making the 6-away point comes out clearly on top in the rollout. Evidently, making home-board points at the first opportunity isn't always the best way to win a gammon.

Anybody have any explanation for why we "die by the sword" in this position? At first I thought that the reason was that when the opponent already has four checkers back, simply bottling them up is enough to create excellent gammon chances. This may be part of the explanation, but even if we move one or even two of White's rear checkers out to White's midpoint, 10/9(3) remains a strong play. So I think there's something else going on as well.

The score (after 0 games) is: gnubg 1, tchow 0 (match to 2 points, Crawford game)

gnubg	180
tchow	136
Position ID: sDNmAA+w5xwDCA Match ID: 8IlEABAAAAAA

#		Ply	Move	Equity
•	1	R	22/21 10/9(3)	+0.841
			0.713 0.208 0.014 - 0.287 0.077 0.006 +0.841 +0.841 0.002 0.002 0.002 - 0.002 0.004 0.001 0.006 0.006
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 844801591 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	10/9(3) 6/5	+0.835 ( -0.007)
			0.712 0.205 0.020 - 0.288 0.073 0.005 +0.835 +0.835 0.002 0.002 0.002 - 0.002 0.004 0.001 0.006 0.006
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 844801591 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	22/21 10/9(2) 6/5	+0.815 ( -0.026)
			0.702 0.205 0.019 - 0.298 0.087 0.006 +0.815 +0.815 0.002 0.002 0.002 - 0.002 0.004 0.001 0.006 0.006
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 844801591 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	10/7 8/7	+0.790 ( -0.051)
			0.713 0.182 0.015 - 0.287 0.064 0.003 +0.790 +0.790 0.002 0.002 0.002 - 0.002 0.004 0.003 0.006 0.006
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 844801591 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	6/4(2)	+0.787 ( -0.054)
			0.723 0.171 0.016 - 0.277 0.057 0.005 +0.787 +0.787 0.002 0.002 0.001 - 0.002 0.003 0.001 0.005 0.005
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 844801591 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

• Stick's sword revisited
  Timothy Chow -- Wednesday, 17 February 2010, at 2:49 a.m.
  • Stick's sword revisited
    Rich Munitz -- Wednesday, 17 February 2010, at 5:51 a.m.
    • Stick's sword revisited
      Ian Shaw -- Wednesday, 17 February 2010, at 10:44 a.m.
      • Stick's sword revisited
        Timothy Chow -- Wednesday, 17 February 2010, at 4:59 p.m.
        • Stick's sword revisited
          Chuck Bower -- Wednesday, 17 February 2010, at 6:08 p.m.
          • Stick's sword revisited
            Timothy Chow -- Wednesday, 17 February 2010, at 6:31 p.m.
        • Stick's sword revisited
          Ian Shaw -- Wednesday, 17 February 2010, at 11:50 p.m.
  • Stick's sword revisited
    lenny -- Wednesday, 17 February 2010, at 6:07 a.m.