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Rollout: Interesting pay now/later problem from rec.games.backgammon

Posted By: Timothy Chow
Date: Tuesday, 3 August 2010, at 2:26 a.m.

In Response To: Interesting pay now/later problem from rec.games.backgammon (Timothy Chow)

There are a couple of interesting things about this position. The first is that on evaluation, all of the bots (Snowie, GNU, XG) seem to think that anything but 13/4 is a big blunder. However, upon rollout, the equities get much closer. It seems that the top play, by a narrow margin, is 13/9 7/2, which I believe very few humans would play. 13/9 7/2 seems to pay now and pay later!

Given the large difference between evaluation and rollout, I wonder whether the rollout can be trusted. Is the bot playing correctly during the rollout?

Someone posted a 1-ply XG rollout on r.g.b. but I would be interested in seeing a stronger XG rollout.

---

The score (after 0 games) is: White 2, Blue 0 (match to 3 points, Crawford game)

White	135
Blue	96
Position ID: mM/BYQAzdwMNAA Match ID: 8Al2ACAAAAAA

• Blue moves 13/9 7/2

#		Ply	Move	Equity
•	1	R	13/9 7/2	+0.373
			0.682 0.112 0.002 - 0.318 0.058 0.003 +0.373 +0.373 0.002 0.003 0.000 - 0.002 0.003 0.001 0.004 0.004
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 896987671 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	13/4	+0.363 ( -0.010)
			0.679 0.058 0.001 - 0.321 0.057 0.001 +0.363 +0.363 0.002 0.002 0.000 - 0.002 0.003 0.000 0.004 0.004
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 896987671 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	13/9 6/1	+0.343 ( -0.030)
			0.667 0.097 0.001 - 0.333 0.069 0.002 +0.343 +0.343 0.002 0.002 0.000 - 0.002 0.004 0.001 0.005 0.005
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 896987671 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	14/9 13/9	+0.338 ( -0.035)
			0.663 0.126 0.003 - 0.337 0.054 0.001 +0.338 +0.338 0.002 0.003 0.001 - 0.002 0.004 0.000 0.003 0.003
			Full cubeful rollout with var.redn.
			1296 games, Mersenne Twister dice gen. with seed 896987671 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

• Interesting pay now/later problem from rec.games.backgammon
  Timothy Chow -- Monday, 2 August 2010, at 3:40 a.m.
  • Interesting pay now/later problem from rec.games.backgammon
    John O'Hagan -- Monday, 2 August 2010, at 5:18 a.m.
  • Interesting pay now/later problem from rec.games.backgammon
    Matt Cohn-Geier -- Monday, 2 August 2010, at 5:19 a.m.
    • Interesting pay now/later problem from rec.games.backgammon
      Casper van der Tak -- Monday, 2 August 2010, at 7:17 a.m.
  • Interesting pay now/later problem from rec.games.backgammon
    Stanley E. Richards -- Monday, 2 August 2010, at 6:20 a.m.
  • Rollout: Interesting pay now/later problem from rec.games.backgammon
    Timothy Chow -- Tuesday, 3 August 2010, at 2:26 a.m.
    • Rollout
      Stick -- Tuesday, 3 August 2010, at 4:59 a.m.