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BGonline.org Forums
OLM 20140520A The Prime Factors
Posted By: kruidenbuiltje In Response To: OLM 20140520A The Prime Factors (Jason Lee)
Date: Wednesday, 21 May 2014, at 10:50 a.m.
Hi Mike,
Even without the inner-board blot 7/5 7/1 would be the better move, I think.
Not only the fives are bad after 10/4 5/3.
The combination of the bar-point with the stripped 6- and 5-point makes other moves bad too.
For instance {61,41} give a 3-2 checker structure on the 6- and 5-point.
And what about {31} should we strip the position further with 4/3 4/1 or go for the 3-2 structure.
So we have 17/36 awkward moves in the future versus 4/36 hits now.
How do we decide where the break-even-point is?
The 4/36 hits equal 144/1296, {65,54} give 20/36 hits, this equals 80/1296.
So the other 13/36 awkward moves have to give 64/1296 hits. That's 5/36 hits on average.
Of the 13/36 awkward moves 7/36 have a gap-on-6 structure and 6/36 have the 3-2 structure.
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The gap-on-6 structure:
{65,61,54,51,41} = 10/36 give direct hits of worth 13/36.
The average hit-worth of this structure is 130/1296 = almost 4/36
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The 3-2 structure:
{D6,65,D5} = 4/36 give direct shots worth 11/36.
The average hit-worth of this structure is 44/1296 say 1/36
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Let's calculate now:
We had 80/1296
The gap-on-6 give us 7/36 x 4/36 = 28/1296
The 3-2 structure gives us 6/36 x 1/36 = 6/1296
Total 114/1296.
As said the hits equal 144/1296.
so without any return-hits you are right and 10/4 5/3 is better.
But even without the 3- and bar-blot blue has blitz-returns: {D3,32,31,D2,21,D1} = 9/36
effectively about 6/36 because of the re-returns.
So the effective hits have a lower value: 124/1296 instead of 144/1296.
So without any blots 10/4 5/3 is a little bit better.
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How is the situation with the indirect return on the bar-blot?
Now we have {16,25,34} = 6/36 + 9/36 = 15/36,
effectively 12/36 because of the re-returns giving 96/1296.
So now 7/5 7/1 is better.
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How about gammons?
What if white didn't have any blots, and we played safe, and we threw {65} or {54}.
White then would have a 20/36 threat, would this be a DP-situation because of a match-winning gammon-threat?
If that is so, then the real value of the these variations would be 72/1296 instead of 40/1296.
This would make 7/1 7/5 better, even in a no-blot situation.
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