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51S-62S-42 and Variants – No Jacoby, No Beavers – 3-ply XG2 Rollouts

Posted By: Taper_Mike
Date: Monday, 16 June 2014, at 1:07 a.m.

In Response To: Running would have been better on the 2nd roll. (Taper_Mike)

		White is Player 2 score: 0 pip: 159 Unlimited Game Jacoby Beaver pip: 167 score: 0 Blue is Player 1
XGID=-a----EaC---dEa--c-e----B-:0:0:1:42:0:0:3:0:10
Blue to play 42

1.	Book1	13/7*	eq: -0.0745
	Player: Opponent: 48.14% (G:13.76% B:0.65%) 51.86% (G:14.49% B:0.81%) Conf.: ±0.0034 (-0.0779...-0.0711) - [100.0%]
2.	Book1	8/4 6/4	eq: -0.0935 (-0.0190)
	Player: Opponent: 47.42% (G:13.09% B:0.50%) 52.58% (G:13.12% B:0.62%) Conf.: ±0.0030 (-0.0965...-0.0905) - [0.0%]
1 Generated by Steven Carey on 4/19/2013 using eXtreme Gammon 2.10 31104 Games rolled with Variance Reduction. Dice Seed: 38795617 Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.10

62S-42

It has long been known that hitting is better than pointing on the second roll in reply to an opening 6-split.

Note that making the 4pt trails by only 19 millipoints of equity, i.e., by 0.019. That’s the margin that must be overcome if making the 4pt is to become the best play in the third-roll position below.

 

		White is Player 2 score: 0 pip: 159 Unlimited Game pip: 161 score: 0 Blue is Player 1
XGID=-a----EaD---dDa--c-e---AA-:0:0:1:42:0:0:0:0:10
Blue to play 42

1.	Rollout1	8/4 6/4	eq: +0.0682
	Player: Opponent: 51.10% (G:15.33% B:0.52%) 48.90% (G:11.48% B:0.51%) Conf.: ±0.0078 (+0.0603...+0.0760) - [100.0%] Duration: 34 minutes 48 seconds
2.	Rollout1	13/7*	eq: +0.0086 (-0.0596)
	Player: Opponent: 49.83% (G:14.81% B:0.72%) 50.17% (G:13.60% B:0.64%) Conf.: ±0.0079 (+0.0007...+0.0165) - [0.0%] Duration: 40 minutes 21 seconds
1 5184 Games rolled with Variance Reduction. Dice Seed: 20853194 Moves: 3-ply, cube decisions: XG Roller

Rollout by Taper_Mike 2014-Jun-14 eXtreme Gammon Version: 2.10.199.2658 51S-62S-42-n-tm.xgp n[P H60] "<=5 n[P H73] "&e

eXtreme Gammon Version: 2.10

51S-62S-42

Adding Blue’s opening 51-split to the mix changes things in a number of ways.

1. Blue is no longer trailing in the race. Making the 4pt assures that his small lead will be preserved.
2. With four Blue checkers on the 8pt, and four rather than five on the midpoint, the natural unstacking play is to make the 4pt. Hitting would leave only one spare on the midpoint, a disadvantage for Blue should a battle for the bar point erupt.
3. Because Blue has an extra spare on his 8pt, making the 4pt will not leave the 8pt stripped. That’s a spare that can be used to attack White’s runner if White chooses to leave it on the bar point. Blue will have good hitting opportunities if White makes a point on his side of the board with 31, 41, or 53. Note that Blue’s opening 51-split has turned the last of these, 53, from a point-maker into a roll that White should use to safety his two outside blots after Blue makes his 4pt.
4. Blue’s split rear checkers increase the number of shots at the White blot on the 14pt from 2 to 6. If White anchors on the bar point, in many cases he will be forced to leave fly shots in the outfield. Making the 4pt prepares a reception committee in case Blue is able to hit one of them.
5. Blue’s split rear checkers increase the number of ways he can advance his anchor.

These advantages combine to create an 80-millipoint swing in favor of making the 4pt. Hitting is now a 60-millipoint error. A similar result holds when White splits with 63 rather than 62.

 

		White is Player 2 score: 0 pip: 159 Unlimited Game pip: 162 score: 0 Blue is Player 1
XGID=-a----EaD---dDa--c-e----B-:0:0:1:42:0:0:0:0:10
Blue to play 42

1.	Rollout1	8/4 6/4	eq: +0.0127
	Player: Opponent: 49.65% (G:14.41% B:0.55%) 50.35% (G:12.23% B:0.54%) Conf.: ±0.0068 (+0.0059...+0.0195) - [100.0%] Duration: 36 minutes 47 seconds
2.	Rollout1	13/7*	eq: -0.0299 (-0.0425)
	Player: Opponent: 49.02% (G:14.56% B:0.69%) 50.98% (G:13.90% B:0.77%) Conf.: ±0.0084 (-0.0383...-0.0214) - [0.0%] Duration: 42 minutes 01 second
1 5184 Games rolled with Variance Reduction. Dice Seed: 20853194 Moves: 3-ply, cube decisions: XG Roller

Rollout by Taper_Mike 2014-Jun-14 eXtreme Gammon Version: 2.10.199.2658 62S-41X-52H-61H-51R-65T-62S-42-n-tm.xgp n[P H43] "<=5 n[P H42] "&e

eXtreme Gammon Version: 2.10

Variant with Fourth Spare on 8pt
62S-41X-52H-61H-51R-65T-62S-42

This variant shows that having a fourth checker on the 8pt is all it takes for pointing to become the better play.

In view of points 1-3 above, this result is not surprising. The margin, however, is about 20 millipoints less than in the original position.

 

		White is Player 2 score: 0 pip: 159 Unlimited Game pip: 166 score: 0 Blue is Player 1
XGID=-a----EaC---dEa--c-e---AA-:0:0:1:42:0:0:0:0:10
Blue to play 42

1.	Rollout1	8/4 6/4	eq: -0.0299
	Player: Opponent: 48.69% (G:13.93% B:0.50%) 51.31% (G:12.32% B:0.54%) Conf.: ±0.0040 (-0.0338...-0.0259) - [100.0%] Duration: 1 hour 59 minutes
2.	Rollout1	13/7*	eq: -0.0486 (-0.0187)
	Player: Opponent: 48.78% (G:13.91% B:0.64%) 51.22% (G:14.33% B:0.67%) Conf.: ±0.0047 (-0.0533...-0.0438) - [0.0%] Duration: 2 hours 18 minutes
1 15552 Games rolled with Variance Reduction. Dice Seed: 20853194 Moves: 3-ply, cube decisions: XG Roller

Rollout by Taper_Mike 2014-Jun-15 eXtreme Gammon Version: 2.10.199.2658 62S-41X-52H-61H-51R-61Z-62S-42-n-tm.xgp n[P H19] "<=15 n[P H23] "&e

eXtreme Gammon Version: 2.10

Variant with Split Checkers
62S-41X-52H-61H-51R-61Z-62S-42

Splitting the rear checkers alone is also enough to make pointing better than hitting.

This result is not as obvious as the foregoing ones, but remember, in the second-roll position, 62S-42, making the 4pt trails hitting by only 19 millipoints. Evidently, the advantages gained by splitting more than compensate for the difference.

Mike

 

Messages In This Thread

• Running would have been better on the 2nd roll.
  Taper_Mike -- Sunday, 15 June 2014, at 12:01 a.m.
  • 51S-62S-42 and variant
    Nack Ballard -- Sunday, 15 June 2014, at 12:59 a.m.
    • 51S-62S-42 and variant
      Taper_Mike -- Sunday, 15 June 2014, at 1:12 a.m.
      • 51S-62S-42 and variant
        Nack Ballard -- Sunday, 15 June 2014, at 1:21 a.m.
        • 51S-62S-42 and variant
          Taper_Mike -- Sunday, 15 June 2014, at 2:18 a.m.
          • 51S-62S-42 and variant
            Nack Ballard -- Monday, 16 June 2014, at 5:01 a.m.
  • Running would have been better on the 2nd roll.
    Timothy Chow -- Sunday, 15 June 2014, at 1:46 a.m.
    • Running would have been better on the 2nd roll.
      neilkaz -- Sunday, 15 June 2014, at 2:44 a.m.
      • Running would have been better on the 2nd roll.
        David Presser -- Sunday, 15 June 2014, at 4:08 a.m.
  • Running would have been better on the 2nd roll.
    Igor -- Sunday, 15 June 2014, at 3:34 p.m.
  • 51S-62S-42 and Variants – No Jacoby, No Beavers – 3-ply XG2 Rollouts
    Taper_Mike -- Monday, 16 June 2014, at 1:07 a.m.
    • 51S-62S-42 and Variants – No Jacoby, No Beavers – 3-ply XG2 Rollouts
      Igor -- Monday, 16 June 2014, at 1:58 a.m.
    • 51S-62S-42 and Variants – No Jacoby, No Beavers – 3-ply XG2 Rollouts
      Daniel Murphy -- Monday, 16 June 2014, at 3:00 a.m.
      • Good variants from Daniel
        Taper_Mike -- Tuesday, 17 June 2014, at 9:58 a.m.
        • Good variants from Daniel
          Taper_Mike -- Wednesday, 18 June 2014, at 3:09 a.m.