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Rollout

Posted By: Daniel Murphy
Date: Sunday, 14 September 2008, at 3:20 p.m.

In Response To: Rollout (Matt Cohn-Geier)

The score (after 0 games) is: Opponent 6, Hero 9 (match to 11 points)

Move number 5: Hero to play 43

Opponent	144
Hero	124
Position ID: bDtggQng2y0MAA Match ID: UQluAWAASAAA

Above, Matt's original position. Matt's at-the-score rollout has 10/7 6/2 winning 5% more games, and as a bonus losing about 2% fewer gammons, so that's the best play at the score.

Matt's rollout also has both 10/7 6/2 and 14/11* 14/10 winning about 26% gammons. A couple of people mentioned gammon wins. I'm sure they realize gammon wins are irrelevant at the score, but since they mentioned gammons I wanted to point out that in interpreting Matt's rollout it's best to completely ignore the gammon win percentages.

Blue doesn't win 26% gammons and it's impossible to tell from the rollout how many gammons Blue wins after either play. It's also impossible to tell from the rollout how many gammons Blue would win after either play at a score where gammons meant something to one or both sides. Since White's gammon losses are as irrelevant to Gnubg in its rollout as they are to Matt's opponent over the board, Gnubg won't bother running off irrelevant gammon losses and, may even resign "gammon" if it estimates White's winning chances at 0% and still has no checkers off.

An example:

The score (after 0 games) is: Opponent 6, Hero 9

Move number 5: Opponent to play 63

Opponent	70
Hero	8
Position ID: bwAAgG23A0AAAA Match ID: EQEPAAAAAAAA

White's play is irrelevant at the score and on 2-ply Gnubg doesn't bother to play 18/9. If you roll out 18/9, Gnubg tells you White loses 47% gammons, a completely bogus number. In a money game, 18/9 would lose than 2% gammons.

In the original position, by the way, 10/7 6/2 is also the best play for money at at Gammon-Go (Blue trails 2-away 1-away Crawford). At both of those scores 14/11* 14/10 does win more gammons, but 10/7 6/2 simply wins many more games. At 2-away 1-away Crawford 14/11* 14/10 wins about 4.2% more gammons but 10/7 6/2 wins about 5.5% more games.

The score (after 0 games) is: Opponent 10, Hero 9 (match to 11 points, Crawford game)

Move number 6: Hero to play 43

Opponent	144
Hero	124
Position ID: bDtggQng2y0MAA Match ID: 8AluAaAASAAA

• Hero moves 10/7 6/2

#		Ply	Move	Equity
•	1	R	10/7 6/2	+0.5312
			0.7203 0.0453 0.0023 - 0.2797 0.0424 0.0019 +0.5312 +0.5312 0.0027 0.0021 0.0006 - 0.0027 0.0058 0.0004 0.0049 0.0049
			Full cubeful rollout with var.redn.
			452 games, Mersenne Twister dice gen. with seed 837694104 and quasi-random dice
			Play: world class 2-ply cubeful prune [world class]
			keep the first 0 0-ply moves and up to 8 more moves within equity 0.16
			Skip pruning for 1-ply moves.
			Cube: 2-ply cubeful prune [world class]
	2	R	14/11* 14/10	+0.5068 ( -0.0244)
			0.6658 0.0876 0.0193 - 0.3342 0.1077 0.0050 +0.5068 +0.5068 0.0036 0.0026 0.0051 - 0.0036 0.0097 0.0014 0.0079 0.0079
			Full cubeful rollout with var.redn.
			451 games, Mersenne Twister dice gen. with seed 837694104 and quasi-random dice
			Play: world class 2-ply cubeful prune [world class]
			keep the first 0 0-ply moves and up to 8 more moves within equity 0.16
			Skip pruning for 1-ply moves.
			Cube: 2-ply cubeful prune [world class]

Messages In This Thread

• MCG vs. Tim Mabee #1
  Matt Cohn-Geier -- Tuesday, 2 September 2008, at 7:36 a.m.
  • Minor correction
    Matt Cohn-Geier -- Tuesday, 2 September 2008, at 3:35 p.m.
  • Rollout
    Matt Cohn-Geier -- Wednesday, 3 September 2008, at 4:28 p.m.
    • Rollout
      Mislav Radica -- Sunday, 7 September 2008, at 9:37 p.m.
      • Rollout
        Stick -- Sunday, 7 September 2008, at 9:55 p.m.
    • Rollout
      Daniel Murphy -- Sunday, 14 September 2008, at 3:20 p.m.
      • Rollouts -- even score
        Daniel Murphy -- Sunday, 14 September 2008, at 5:12 p.m.