Re: [ublas] Fwd: boost/numeric/bindings/lapack

Subject: Re: [ublas] Fwd: boost/numeric/bindings/lapack
From: Thomas Klimpel (Thomas.Klimpel_at_[hidden])
Date: 2008-11-13 07:45:35

Hi Vardan,

> It's been long time since I wrote this, but I'm pretty sure the
> original code is correct. Accourding to the documentation of SGBTRF
> (http://www.netlib.org/lapack/explore-html/sgbtrf.f.html ), the AB
> matrix is of dimension (LDAB, N), where LDAB >= 2*KL+KU+1. To achieve
> this dimension the original banded matrix A must have allocated KL
> lower and KL+KU upper diagonals.

I see. So the name "a" for the matrix is misleading, since it is the
matrix "ab" in reality. Now I ask myself how to map the matrix "a" into
the matrix "ab". I would certainly hope for a(i,j)=ab(i,j), but I get
the impression that it's something like a(i,j)=ab(i,j+kl). Do you still
remember the exact mapping? (I would also be happy if you tell me that
the mapping is indeed a(i,j)=ab(i,j).)

Regards,
Thomas