[SciPy-dev] band matrix wrapping ready for inclusion

[Arnd Baecker]

On Fri, 30 Jun 2006, Nils Wagner wrote:

> Arnd Baecker wrote:
> > On Thu, 29 Jun 2006, Travis Oliphant wrote:
> >
> >
> >> Arnd Baecker wrote:
> >>
> >>> Hi,
> >>>
> >>> sorry for asking again, but I would really be happy
> >>> to get this finished...
> >>>
> >>> Travis, Robert or Pearu: may I go ahead with integrating
> >>> the band matrix wrappers into scipy svn?
> >>>
> >>>
> >> I say go ahead.  It looks like an additional feature with a reasonable
> >> interface that should not affect other code.
> >>
> >
> > Many thanks, code is commited. All tests pass without problems.
> >
> > Best, Arnd
> > _______________________________________________
> > Scipy-dev mailing list
> > Scipy-dev at scipy.org
> > http://projects.scipy.org/mailman/listinfo/scipy-dev
> >
>  Hi Arnd,
>
> Thank you very much for the support of band matrices in scipy. That is
> very useful.
> BTW, is it possible to convert full matrices to band matrices and vice
> versa ?

Yes.
For an example of the conversion of a full matrix to band
see Lib/linalg/tests/test_decomp.py
where you find code blocks like

        # Extract upper bands from symmetric and hermitian band matrices
        # (for use in dsbevd, dsbevx, zhbevd, zhbevx
        #  and their single precision versions)
        LDAB = self.KU + 1
        self.bandmat_sym  = zeros((LDAB, N), dtype=float)
        self.bandmat_herm = zeros((LDAB, N), dtype=complex)
        for i in xrange(LDAB):
            self.bandmat_sym[LDAB-i-1,i:N]  = diag(self.sym_mat, i)
            self.bandmat_herm[LDAB-i-1,i:N] = diag(self.herm_mat, i)

HTH,

Arnd