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Re: [Help-gsl] How does this cycle https://github.com/ampl/gsl/blob/mast


From: Patrick Alken
Subject: Re: [Help-gsl] How does this cycle https://github.com/ampl/gsl/blob/master/linalg/svd.c#L117 work?
Date: Mon, 19 Jun 2017 11:35:55 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1

I don't know the answer to your question, but its probably more helpful
to take a look at the SVD algorithm description in Golub and Van Loan,
on which the GSL code is probably based. Also its probably worthwhile to
look at the original paper, which I found here:

http://people.duke.edu/~hpgavin/SystemID/References/Golub+Reinsch-NM-1970.pdf

There is a complete pseudo-code writeup given in section 4.

Patrick

On 06/16/2017 04:19 PM, Marco Ippolito wrote:
> Hi all
> I do not undderstand this while cycle :
> https://github.com/ampl/gsl/blob/master/linalg/svd.c#L117
>
> It seems to me that the only time when b is decremented is here:
> https://github.com/ampl/gsl/blob/master/linalg/svd.c#L123
> so when fbm1 == 0.0 where fb1 is the value of f at index = b-1 :
> https://github.com/ampl/gsl/blob/master/linalg/svd.c#L119
>
> Since I'm trying to write my own C++11 code based on GSL code, I would like
> to understand how it can work.
> Any ideas?
>
> Looking forward to your kind help.
> Marco





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