[Help-gsl] Re: QR Decomposition for a matrix with complex values

[Jonny Taylor]

In 2005, Brian Gough wrote:
> It is possible to do Complex QR decomposition, the algorithm is the
> same as for real QR.  See Golub and Van Loan "Matrix Computations" for
> details.  As far as I know, nobody is working on adding it to GSL
> though.
Apologies for resurrecting a very old message! I was looking at  
complex QR decomposition the other day, and wondered if you could  
elaborate on this a bit.

I have a copy of Golub & van Loan (2nd edition) here, and as far as I  
can see it only talks about real QR decomposition. Did you have a  
part in mind where it talks specifically about complex decomposition?  
I ask because I tried to convert the GSL real QR decomp code by  
basically converting every line to its complex equivalent, and didn't  
get the correct results.

I don't know if I made a mistake in the "translation", or whether  
there is some extra catch to doing the complex decomposition. For the  
moment I've avoided the issue by doing the trivial conversion of my  
complex matrix to a real matrix that's twice as large. I'd be  
interested to work out why the "proper" way didn't work, though.

Thanks for any suggestions
Jonny