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Gammon Save Play 52 **ROLLOUT** and Commentary

Posted By: Michael Depreli
Date: Tuesday, 22 January 2013, at 11:24 a.m.

In Response To: Gammon Save Play 52 (Michael Depreli)

		White is Player 2 score: 0 pip: 128 2 point match Crawford pip: 145 score: 1 Blue is Player 1
XGID=---B--DbB-A--Ea--bee----A-:0:0:1:52:1:0:1:2:10
Blue to play 52

1.	Rollout1	24/22 13/8	eq: -0.498
	Player: Opponent: 40.85% (G:7.88% B:1.06%) 59.15% (G:15.76% B:0.64%) Conf.: ± 0.008 (-0.506...-0.490) - [100.0%] Duration: 1 minute 59 seconds
2.	Rollout1	24/22 10/5	eq: -0.528 (-0.030)
	Player: Opponent: 40.32% (G:7.85% B:0.61%) 59.68% (G:16.71% B:0.60%) Conf.: ± 0.008 (-0.536...-0.519) - [0.0%] Duration: 1 minute 53 seconds
3.	Rollout1	13/8 10/8	eq: -0.548 (-0.050)
	Player: Opponent: 37.86% (G:6.70% B:0.44%) 62.14% (G:15.25% B:0.39%) Conf.: ± 0.008 (-0.555...-0.540) - [0.0%] Duration: 1 minute 50 seconds
4.	Rollout1	13/8 6/4	eq: -0.559 (-0.060)
	Player: Opponent: 39.71% (G:9.74% B:1.07%) 60.29% (G:17.65% B:0.42%) Conf.: ± 0.008 (-0.566...-0.551) - [0.0%] Duration: 1 minute 59 seconds
5.	Rollout1	13/11 10/5	eq: -0.573 (-0.075)
	Player: Opponent: 39.38% (G:9.53% B:0.82%) 60.62% (G:18.04% B:0.85%) Conf.: ± 0.009 (-0.582...-0.565) - [0.0%] Duration: 1 minute 56 seconds
6.	Rollout1	10/5 6/4	eq: -0.590 (-0.092)
	Player: Opponent: 39.02% (G:8.28% B:0.81%) 60.98% (G:18.53% B:0.69%) Conf.: ± 0.009 (-0.599...-0.582) - [0.0%] Duration: 1 minute 46 seconds
1 756 Games rolled with Variance Reduction. Moves and cube decisions: 3-ply

eXtreme Gammon Version: 2.03, MET: Kazaross XG2

Firstly let's see why 10/5 6/4 is such a weak play.

All of white's next rolls except 52, 51 and 41 will create inner board points plus some will either extend his prime or point on blue.
Some of those 42,31,63,53,64 will leave indirect shots but now blue has the liability of two inner board blots which also leaves white free to attack on the ace with his three poorest rolls (52, 51, 41).

Firstly blue should step up to the 22 point, although he won't like being pointed on he gains by neutralizing some of the power of white's 8 point, 42 and 64 don't play so well plus it makes 66 a much poorer roll.
The second reason blue needs to step up to the 22 point is that if he's not on the bar (or white rolls 55) and rolls a six he will have the luxury of jumping out of harms way.

So which 5 to play? We only need to focus on rolls that hit with a 3 or 21.
21: White will make the 5 point in both positions
53: White will point in both positions (hitting if blue leaves the blot on the 10 is too risky, blue does have a stronger board with no inner blots to worry about
43,32: White will point in both positions
33: This is already an excellent roll so white doesn't gain much here in terms of equity plus it's a toss up to whether he should play 7/4(2) 6/3*(2) or 18/15*(2) 6/3*(2).
31: This is a relatively poor roll in both scenarios with quite a few plausible plays hitting inside with the 3 seems stronger than hitting on the 10 should blue leave the blot there.
63: Again whether to hit the blot on the 10 is a borderline decision but either way white doesn't gain much.

So we can now see white actually doesn't have any rolls where hitting on the 10 is mandatory and clear.
Obviously if blue ends up on the bar he would prefer not to have the blot on the 10 but having it on the 5 still leaves him exposed especially without a spare builder on the 8. One additional benefit of playing 24/22 13/8 is that blue will use upcoming 3's to create a useful blocking point.

Michael