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BGonline.org Forums
Prime Time revisited
Posted By: Nack Ballard In Response To: Prime Time revisited (Nack Ballard)
Date: Wednesday, 23 December 2009, at 8:33 p.m.
In my original analysis, comparing 13/9 8/7 to 11/7 8/7, I hallucinated White's 2 dupli-/diversifi-cation after being hit; (3) is negated. Also, in my (2) reason, I wrongly assumed (after 13/9 8/7) that Blue should make a six-prime with 42, when actually he should hit loose. Half of (2) remains: Blue breaks the 7pt with 62 61 one way and with only 42 the other way. But (2) and (3) were never intended to be more than a supplemental bonus -- I could have easily left them off, even if fully valid.
My (1) (highest priority) reason in support of 13/9 8/7 relative to 11/7 8/7 was and is return shots. To be more specific, after 11/7 8/7 when White escapes Blue gets 7/1296 return shots (63-11, 62-21, 62-22, 62-11, 61-22, 61-11), whereas after 13/9 8/7 when White escapes Blue gets 64/1296 return shots (42 or 41 met by any of 52 51 42 41 32 31 21 22 11).
The quality of the return shots is lower with a six-prime missing the 7pt compared to a consecutive five-prime, because with the latter Blue has more return-returns and escape possibilities surviving White's return shots, and (as Mochy points out) if Blue hits on the 1pt, White might hit back with 62 61 on the front edge of the prime. But at this score, just getting the return shots (64/1296 - 7/1296 = 4.4% extra) is big. In my view, this factor must make 13/9 8/7 a powerful enough contender to include in a rollout even if it's not the best play (an issue which is still unresolved -- the Snowie rollout I will post soon is in violent conflict with the Gnu rollout previously posted).
Nack
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