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Automatically calculating skew   Message List  
Reply | Forward Message #2418 of 2468 |
Re: [ggnfs] Re: Automatically calculating skew

Quoting chris2be8 <chris2be8@...>:

> ggnfs-doc.pdf page 17 says "It should be at least 1". So I assumed I should
> invert the result if less than 1.

The skew being larger than 1 is a good rule of thumb, and is especially
useful becase the rest of the code assumes relations will have an 'a'
coordinate much larger than the 'b' coordinate. If the skew was much
smaller than 1 then the postprocessing code would fail to parse many relations.

However, even when the optimal skew should legitimately be smaller than 1,
it is never *much* smaller, so skew < 1 is not a big problem.

jasonp

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Sun Jun 21, 2009 10:06 pm

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Message #2418 of 2468 |
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Hello, I've written a patch for factMsieve.pl to automatically calculate skew if it isn't provided in the .poly file for a SNFS job. It should also work for...
chris2be8
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Jun 19, 2009
7:05 pm

... Ok, makes sense. Except that it doesn't have to flipped. It is always (|c0|/|cn|)**(1/n) (i.e. can be less than 1). I'll post it. Thanks. --Serge...
Serge Batalov
batalovs
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Jun 20, 2009
8:09 pm

... ggnfs-doc.pdf page 17 says "It should be at least 1". So I assumed I should invert the result if less than 1. At least that's was the "Draft of February 8,...
chris2be8
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Jun 21, 2009
3:44 pm

... The skew being larger than 1 is a good rule of thumb, and is especially useful becase the rest of the code assumes relations will have an 'a' coordinate...
Jason Papadopoulos
jasonp@...
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Jun 21, 2009
10:07 pm
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