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Rollout: When is it right to hit loose with 6/1*?

Posted By: Timothy Chow
Date: Thursday, 15 April 2010, at 1:18 a.m.

In Response To: When is it right to hit loose with 6/1*? (Timothy Chow)

OTB, I played 9/3 here. Significantly ahead in the race, Blue would like to play safe even if it's somewhat awkward. For example if Blue's spare were on the 8-point instead of the 9-point then 9/8 9/4 would be the right way to play a 5-1 despite the seemingly awkward stacks that result. But Blue cannot play safely and so must choose the lesser of two evils. Playing 9/3 looks prettier but leaves more immediate shots and the blot isn't guaranteed to be covered next time. By contrast, 9/8 6/1* forces White's blot forward and is likely to make future safe plays easier if Blue is not hit back immediately. The rollout puts 9/8 6/1* on top. See the first diagram below.

The game continued with my opponent rolling 6-3 hitting, and then I had to come in from the bar with 3-1. See the second diagram below. Here I made another error by playing bar/24 6/3*. The simple bar/21 is better. The race is now even, and it's not good to risk getting another checker sent back when a sound alternative is available. Also, White's blot is less troublesome on the 3-point than on the ace point.

Chase's rule of thumb for playing against anchor-and-guard (use the first awkward roll to hit) is interesting. It works well in the third position diagrammed below, which is a variant of a position from Robertie's book, and which stumped several Giants when I posted it here last year.

---

gnubg	165
tchow	143
Position ID: sDPLgCGYZ4cBBg Match ID: cIkUAIAAAAAA

#		Ply	Move	Equity
•	1	R	9/8 6/1*	-0.208
			0.446 0.105 0.003 - 0.554 0.111 0.005 -0.115 -0.208 0.001 0.001 0.000 - 0.001 0.001 0.000 0.003 0.007
			Full cubeful rollout with var.redn.
			2592 games, Mersenne Twister dice gen. with seed 848449780 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	9/3	-0.245 ( -0.037)
			0.437 0.096 0.003 - 0.563 0.110 0.004 -0.140 -0.245 0.001 0.001 0.001 - 0.001 0.001 0.000 0.003 0.007
			Full cubeful rollout with var.redn.
			2592 games, Mersenne Twister dice gen. with seed 848449780 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]

---

gnubg	157
tchow	159
Position ID: cGfGgAmYZ8MAQw Match ID: cIkMAIAAAAAA

#		Ply	Move	Equity
•	1	R	bar/21	-0.223
			0.441 0.097 0.004 - 0.559 0.107 0.004 -0.130 -0.223 0.001 0.001 0.000 - 0.001 0.001 0.000 0.003 0.006
			Full cubeful rollout with var.redn.
			2592 games, Mersenne Twister dice gen. with seed 848327114 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	bar/24 6/3*	-0.265 ( -0.042)
			0.436 0.099 0.004 - 0.564 0.138 0.007 -0.169 -0.265 0.001 0.001 0.000 - 0.001 0.001 0.001 0.003 0.008
			Full cubeful rollout with var.redn.
			2592 games, Mersenne Twister dice gen. with seed 848327114 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]

---

Variant of Robertie's position 46 of 501

gnubg	172
tchow	163
Position ID: 4HPwACPgc+QBJA Match ID: cIkKAAAAAAAA

#		Ply	Move	Equity
•	1	R	13/11 6/1*	+0.047
			0.513 0.127 0.005 - 0.487 0.128 0.006 +0.024 +0.047 0.001 0.001 0.000 - 0.001 0.001 0.000 0.003 0.006
			Full cubeful rollout with var.redn.
			5184 games, Mersenne Twister dice gen. with seed 870705514 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	13/11 13/8	+0.020 ( -0.026)
			0.511 0.124 0.005 - 0.489 0.132 0.005 +0.012 +0.020 0.001 0.001 0.000 - 0.001 0.001 0.000 0.002 0.006
			Full cubeful rollout with var.redn.
			5184 games, Mersenne Twister dice gen. with seed 870705514 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	24/22 13/8	+0.004 ( -0.043)
			0.502 0.120 0.005 - 0.498 0.119 0.004 +0.005 +0.004 0.001 0.001 0.000 - 0.001 0.001 0.001 0.002 0.006
			Full cubeful rollout with var.redn.
			5184 games, Mersenne Twister dice gen. with seed 870705514 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

• When is it right to hit loose with 6/1*?
  Timothy Chow -- Wednesday, 14 April 2010, at 4:53 a.m.
  • When is it right to hit loose with 6/1*?
    Chase -- Wednesday, 14 April 2010, at 5:05 a.m.
  • Rollout: When is it right to hit loose with 6/1*?
    Timothy Chow -- Thursday, 15 April 2010, at 1:18 a.m.