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BGonline.org Forums
Rollout
Posted By: Daniel Murphy In Response To: Rollout (Timothy Chow)
Date: Friday, 9 October 2009, at 3:13 p.m.
Oops, you are right. I misread the text. Robertie writes "Black felt pretty good here and played 13/12*/8. Obvious, but careless. A better play was 13/12* 7/3, getting four builders for the ace point." He doesn't mention 13/12* 8/4. I got entangled in conveying a quibble about the book, which is that often the explanations mention one bad play and one correct solution, but nothing at all about a third or fourth play that is at least as reasonable as the wrong play that's mentioned. In problem 64, the two top plays to me were 7/3 and 8/4; 12/8 didn't look right at all.
About 6-6 -- I didn't write "main explanation," but pointed out that it doesn't blot after 8/4. It's a very good number after 8/4, and bad number afer 7/3. Meanwhile, 7/3 is marginally better some percentage of the time that Blue rolls one of his 5/36 numbers that make the acepoint after 7/3 but not after 8/4.
It's difficult to add and compare guesstimated percentages of percentages of percentages. But I think it's good to remember that "only" one bad roll is one out of 36, and 1/36 is not zero, it's 2.77%. A portion of 2.77% can be relatively sizable. Your rollouts show little difference between all three plays. There's only 0.013 difference in equity between 8/4 and 7/3, which is the gammonless equivalent of one play winning 0.65% more than the other. Although I'm not even sure that the balance of a bad 6-6 vs. five additional pointmaking rolls favors 8-4, it's not hard for me to believe that if it is, that it accounts for some portion of that 0.65%, or 0.013 equity.
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