[GRASS-dev] BLAS/LAPACK (Part II)

[Daniel Bundala]

Guys,

It is quite interesting, but I have had plans to replace v.generalize
matrix code by "yours" library code. I have not studied G_matrix_*
code carefully, but it seems to me that it is superior.

Firstly, Soeren wrote that the current code is multithreaded.
Secondly, someone mentioned, that it supports the sparse matrices.
Support of sparse matrices would increase the efficiency of
v.generalize since it uses only the sparse matrices.
Thirdly, Soeren mentioned that the current code supports many methods
my code doesnt support. To tell the truth, I have never heard about
many of them (Well, I am still (young) student...)

The only thing I am missing in the current code is the direct access
to the elements of a matrix. But, this is quite dangerous and I really
doubt whether this is a good API-desing.

On the other hand, it is true that the current code is quite obscure,
say. Also, it is tempting to replace fortran code by C code.
Therefore, my suggestons are: clean library code and replace the
current code by v.generalize code only if it is really faster. Some
benchmarks are probably required, but I doubt that my code beats
(optimized) library code.

Daniel

On 8/20/07, Markus Neteler <neteler at itc.it> wrote:
> Hi Soeren,
>
> from my users point of view this sounds excellent. please go ahead...
> You had already suggested it and there were apparently no
> objections.
>
> thanks
> Markus
>
> On Mon, Aug 20, 2007 at 05:20:18PM +0200, "Sören Gebbert" wrote:
> > HI folks,
> >
> > -------- Original-Nachricht --------
> > > Datum: Mon, 20 Aug 2007 12:29:14 +0300
> > > Von: Wolf Bergenheim <wolf+grass at bergenheim.net>
> > > An: GRASS Devel <grass5 at grass.itc.it>
> > > CC: Daniel Bundala <daniel.bundala at oriel.ox.ac.uk>, Brad Douglas <rez at touchofmadness.com>
> > > Betreff: Re: [GRASS-dev] BLAS/LAPACK (Part II)
> >
> > > On 17.08.2007 07:09, Brad Douglas wrote:
> > > >
> > > > What I propose is moving the matrix code from v.generalize
> > >
> > > +1
> > >
> > > > (in particular, matrix_inverse() ) to lib/gmath and simplifying the
> > > existing
> > > > MATRIX structure.
> > > >
> >
> > I can easily integrate the matrix code from v.generailze into
> > the gpde library, because the existing matrix structures are quite
> > similar. Quadratic and sparse matrices are supported.
> > The gpde library ships several vector-matrix and vector-vector
> > functions with it, but currently as static functions within the krylov-space solvers. I can make them public (extern),
> > so they can be accessed from out side of the krylov solvers.
> >
> > Many linear equation solvers are available
> > within the gpde library:
> > * direct solvers
> > ** gauss elimination
> > ** lu decomposition
> > ** cholesky decomposition.
> > * iterative solvers
> > ** gauss seidel / SOR
> > ** jacobi
> > ** conjugate gradients (krylov space method)
> > ** preconditioned conjugate gradients (krylov space method)
> > ** biconjugate gradients stabilized (krylov space method)
> >
> > Everything is multithreaded with OpenMP (solver, matrix, vector operations and some array functions).
> >
> > And as you know, the lu code in gmath lib is a copy
> > of the numerical recipes algorithm and not free.
> >
> > I would like to hear some suggestions.
> >
> > Best regards
> > Soeren
> >
> >
> > >
> > > I think that would be a good idea, especially if you also want to use
> > > that code. It is easier to maintain the code in one place.
> > >
> > > Brad do you know of any additional mathematics or similar things you'd
> > > like to see in lib/gmath? Perhaps next year it could be a Summer of Code
> > > project to add them ;)
> > >
> > > --Wolf
> > >
> > > --
> > >
> > > <:3 )---- Wolf Bergenheim ----( 8:>
> > >
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> --
> Markus Neteler  <neteler itc it>  http://mpa.itc.it/markus/
> FBK-irst -  Centro per la Ricerca Scientifica e Tecnologica
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