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OLM 20140520A The Prime Factors

Posted By: kruidenbuiltje
Date: Wednesday, 21 May 2014, at 10:50 a.m.

In Response To: OLM 20140520A The Prime Factors (Jason Lee)

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:

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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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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