BGonline.org Forums

Rollout: Run the back checker?

Posted By: Timothy Chow
Date: Sunday, 18 July 2010, at 12:17 a.m.

In Response To: Run the back checker? (Timothy Chow)

I (correctly) decided that running into the outfield was the wrong idea here, despite being ahead in the race and having a slightly better board. White's position is rather inflexible here and there's a good chance that White will have to leave an indirect shot. Running into the outfield just gives White a chance to hit loose and consolidate.

I played 13/5, trying to build my board. The rollout indicates that this is second best, but the difference in equity appears to be quite substantial. The trouble is that after 13/7, there is no way to play the 2 up front in a clearly constructive way. Thus 24/22 13/7 seems to be best. Stepping up does not really give White any more good rolls and it provides slightly better coverage of the outfield.

For comparison, I have also included a 4-ply analysis of a variant position where Blue's blot on the 1 point is moved to the 4 point. Then 13/7 6/4 seems to be best by a small margin. Note that once Blue has a strong four-point board then challenging White with 24/18 becomes a viable option.

---

gnubg	132
tchow	125
Position ID: OB/MIwCNncEDIA Match ID: cAkLAEAAKAAA

#		Ply	Move	Equity
•	1	R	24/22 13/7	+0.116
			0.543 0.094 0.002 - 0.457 0.064 0.002 +0.114 +0.116 0.001 0.002 0.000 - 0.001 0.001 0.000 0.003 0.006
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 890540859 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	13/5	+0.031 ( -0.085)
			0.515 0.112 0.002 - 0.485 0.071 0.002 +0.071 +0.031 0.001 0.002 0.000 - 0.001 0.001 0.000 0.003 0.006
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 890540859 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 8/2	+0.021 ( -0.095)
			0.512 0.112 0.002 - 0.488 0.089 0.003 +0.048 +0.021 0.001 0.002 0.000 - 0.001 0.001 0.000 0.003 0.006
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 890540859 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	13/7 8/6	-0.008 ( -0.124)
			0.506 0.115 0.002 - 0.494 0.078 0.003 +0.047 -0.008 0.001 0.002 0.000 - 0.001 0.001 0.000 0.003 0.006
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 890540859 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	13/7 6/4	-0.021 ( -0.136)
			0.504 0.113 0.002 - 0.496 0.076 0.003 +0.045 -0.021 0.001 0.002 0.000 - 0.001 0.001 0.000 0.003 0.006
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 890540859 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]
	6	R	24/16	-0.050 ( -0.165)
			0.494 0.078 0.002 - 0.506 0.076 0.003 -0.011 -0.050 0.001 0.001 0.000 - 0.001 0.001 0.000 0.002 0.005
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 890540859 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 position:

gnubg	132
tchow	128
Position ID: OB/MIwCmncEDIA Match ID: cAkZAEAAKAAA

#		Ply	Move	Equity
	1	4	13/7 6/4	+0.209
			0.558 0.098 0.001 - 0.442 0.043 0.001
	2	4	24/18 6/4	+0.201 ( -0.009)
			0.559 0.079 0.002 - 0.441 0.042 0.001
	3	4	24/22 13/7	+0.196 ( -0.014)
			0.559 0.087 0.001 - 0.441 0.051 0.001
	4	4	13/5	+0.154 ( -0.055)
			0.540 0.112 0.002 - 0.460 0.058 0.002

Messages In This Thread

• Run the back checker?
  Timothy Chow -- Friday, 16 July 2010, at 10:11 p.m.
  • Run the back checker?
    Marv Porten -- Friday, 16 July 2010, at 10:47 p.m.
  • Rollout: Run the back checker?
    Timothy Chow -- Sunday, 18 July 2010, at 12:17 a.m.