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Rollout: Scrambling two checkers

Posted By: Timothy Chow
Date: Monday, 28 June 2010, at 2:42 a.m.

In Response To: Scrambling two checkers (Timothy Chow)

Not so long ago, I would have played 14/8 automatically and then looked around for the best 2, without even considering 23/15. However, having missed a couple of plays like this before, I noticed OTB that my opponent's midpoint was stripped, and that if I were missed then I would have a solid advantage. I played 23/15. The short rollout below suggests that 23/15 is slightly inferior to the prosaic 14/6, though the two plays are close, and a longer rollout is needed to separate them.

More importantly, however, what I failed to consider carefully OTB was the location of my opponent's anchor. I would have played 23/15 if my opponent had either a 2-point anchor or a 4-point anchor. As it turns out, 23/15 is hugely right against a 2-point anchor and a big mistake against a 4-point anchor. (See the rollouts below.) Against a 4-point anchor, 23/15 does not gain as much if it works, and it loses more when it doesn't work (plus there are extra fly shots from the anchor to worry about). Against a 2-point anchor, 23/15 gains a lot if it works and loses less when it doesn't work (and there are no fly shots from the anchor). The moral is that, when plopping down two blots in the outfield, it's just as important to look at the opponent's anchor as it is to look at the opponent's stripped midpoint.

---

Posted position:

gnubg	138
tchow	142
Position ID: zM6GAQyw28EFEA Match ID: cAkZAFAAMAAA

#		Ply	Move	Equity
•	1	R	14/6	+0.062
			0.524 0.110 0.005 - 0.476 0.140 0.003 +0.020 +0.062 0.001 0.001 0.000 - 0.001 0.002 0.000 0.003 0.009
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 890197537 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	23/15	+0.051 ( -0.011)
			0.532 0.087 0.005 - 0.468 0.171 0.004 -0.020 +0.051 0.001 0.001 0.000 - 0.001 0.001 0.000 0.003 0.009
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 890197537 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	14/8 13/11	+0.033 ( -0.029)
			0.521 0.106 0.005 - 0.479 0.153 0.004 -0.003 +0.033 0.001 0.001 0.000 - 0.001 0.002 0.000 0.003 0.009
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 890197537 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	23/21 14/8	-0.088 ( -0.151)
			0.490 0.116 0.006 - 0.510 0.179 0.003 -0.079 -0.088 0.001 0.001 0.000 - 0.001 0.002 0.000 0.004 0.009
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 890197537 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]

---

Against a 4-point anchor:

gnubg	136
tchow	142
Position ID: zM6GAQaw28EFEA Match ID: cAkZAFAAMAAA

#		Ply	Move	Equity
•	1	R	14/6	-0.225
			0.453 0.071 0.003 - 0.547 0.142 0.002 -0.164 -0.225 0.001 0.001 0.000 - 0.001 0.002 0.000 0.003 0.008
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 892441810 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	14/8 13/11	-0.255 ( -0.031)
			0.449 0.079 0.004 - 0.551 0.163 0.004 -0.185 -0.255 0.001 0.001 0.000 - 0.001 0.002 0.000 0.003 0.008
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 892441810 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	23/21 14/8	-0.288 ( -0.064)
			0.448 0.086 0.004 - 0.552 0.184 0.003 -0.202 -0.288 0.001 0.001 0.000 - 0.001 0.002 0.000 0.003 0.008
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 892441810 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	23/15	-0.297 ( -0.073)
			0.444 0.059 0.002 - 0.556 0.191 0.004 -0.246 -0.297 0.001 0.001 0.000 - 0.001 0.002 0.000 0.003 0.009
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 892441810 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]

---

Against a 2-point anchor:

gnubg	140
tchow	142
Position ID: zM6GARiw28EFEA Match ID: cAkZAFAAMAAA

#		Ply	Move	Equity
•	1	R	23/15	+0.473
			0.642 0.118 0.006 - 0.358 0.129 0.003 +0.275 +0.473 0.001 0.002 0.001 - 0.001 0.001 0.000 0.004 0.010
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 889220262 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	14/8 13/11	+0.340 ( -0.133)
			0.602 0.152 0.007 - 0.398 0.137 0.004 +0.223 +0.340 0.001 0.002 0.000 - 0.001 0.002 0.000 0.004 0.010
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 889220262 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	14/6	+0.336 ( -0.137)
			0.597 0.153 0.008 - 0.403 0.133 0.003 +0.218 +0.336 0.002 0.002 0.000 - 0.002 0.002 0.000 0.004 0.011
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 889220262 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	23/21 14/8	+0.272 ( -0.201)
			0.586 0.146 0.008 - 0.414 0.154 0.003 +0.169 +0.272 0.001 0.002 0.000 - 0.001 0.002 0.000 0.004 0.011
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 889220262 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

• Scrambling two checkers
  Timothy Chow -- Sunday, 27 June 2010, at 4:08 a.m.
  • Scrambling two checkers
    Casper van der Tak -- Sunday, 27 June 2010, at 6:30 a.m.
  • Scrambling two checkers
    christian munk-christensen -- Sunday, 27 June 2010, at 4:41 p.m.
  • Scrambling two checkers
    garyo -- Monday, 28 June 2010, at 1:43 a.m.
  • Rollout: Scrambling two checkers
    Timothy Chow -- Monday, 28 June 2010, at 2:42 a.m.
    • Longer rollout
      Timothy Chow -- Tuesday, 29 June 2010, at 9:34 p.m.
  • Scrambling two checkers
    neilkaz -- Monday, 28 June 2010, at 2:52 a.m.