DOLFIN

QR Matrix decomposition

Asked by Melanie Jahny

I just want to know if there are any already implemented
algorithms in Fenics which I can use for a QR-decomposition
of a matrix?

Thanks!

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Garth Wells
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Garth Wells (garth-wells) said : 		#1

Armadillo has a very simple interface for dense linear algebra and supports QR factorisation:

    http://arma.sourceforge.net/

DOLFIN depends on armadillo, so is already configured to use it. There are some examples in dolfin/adaptivity (search for arma::).

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Melanie Jahny (melanie-jahny) said : 		#2

Thank you for the answer, but I cannot find any file containing
arma::. I found some in the fenics book preprint, but only for
c++ code. Can I also use it the python environment? Could you
give me an example?

Thanks a lot, Melanie

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Best Garth Wells (garth-wells) said : 		#3

From Python, use the numpy QR factorisation or least-squares solver.

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Melanie Jahny (melanie-jahny) said : 		#4

Thanks a lot for the good advice!