good chemistry is complicated,
and a little bit messy -LW
Re^6: Algorithm for cancelling common factors between two lists of multiplicandsby BrowserUk (Pope)
|on Aug 09, 2005 at 00:03 UTC||Need Help??|
... is there a reason you aren't using the Chi-square test?
I'm not trying to solve the sample problem. That was just an example I found on the web and used as a test.
I set out to solve the problem of performing the FET using Perl. First I did it with Math::Pari, but which gives a result of 8.070604647867604097576877668E-7030 in 26ms, but I was unsure about the accuracy. It also imposes a binary dependancy.
So, then I coded it using Math::BigFloat
But that ran for 20 minutes without producing any output before I killed it (I've set it running again now, and my machines fan has been thrashing at full speed for the last 25 minutes).
Whilst I was waiting for the BigFloat version, I coded this version which attempts to reduce the size of the problem by eliminating (exactly common) factors:
This works well for values smallish values, but cannot handle the example I gave above (NV overflow).
It was then I started thinking about how to eliminate more factors from the equation so as to reduce the size of the intermediate terms, and posted my SoPW. I think that hv's solution of expanding all terms to their prime factorizations before performing the cancelling out will be a winner--but I haven't finished coding that yet.
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