Re: [ublas] Banded matrix storage

Subject: Re: [ublas] Banded matrix storage
From: pmamales_at_[hidden]
Date: 2013-08-01 13:05:04

If I can add my two cents,
when the matrix is row-major, one can automatically get the "diagonals"
as contiguous arrays, off their respective starting points.
So, one can thing of them as in diagonal format, only the buffers have 
been allocated all in one go ;-)
HTH,
Petros

PS: Although I asked a very-related question, I did not see any answer, so I thought it was ignored as 
trivial/already answered elsewhere. However, I did receive these very relevant emails. Am I doing something wrong ?

---- Rutger ter Borg <rutger_at_[hidden]> wrote: 
> 
> On 2013-07-31 17:22, Nasos Iliopoulos wrote:
> > Gunter,
> > I am working on this bug, but based on the test case I am wondering why
> > should the expected row-major data layout be:
> >
> > 0, 0, 11, 12, 0, 21, 22, 23, 31, 32, 33, 34, 42, 43, 44, 45, 53, 54, 55, 0
> >
> > And not
> >
> > 0, 12, 23, 34, 45, 11, 22, 33, 44, 55, 21, 32, 43, 54, 0, 31, 42, 53, 0, 0 ?
> >
> > For the moment I got the column-major implementation working as
> > expected, but I need to add some more tests cases to make sure it is
> > working for non-square matrices as well.
> >
> > Regards,
> >
> > -Nasos
> >
> 
> 
> Hey Nasos,
> 
> great work. The data in banded matrices is stored either row-by-row 
> (row-major), or column-by-column (column-major). This is defined by 
> netlib. AFAIK, a diagonal-by-diagonal storage scheme is not supported by 
> CBLAS.
> 
> Cheers,
> 
> Rutger
> 
> 
> 
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