about KSP based on parallel dense matrix

[Yujie]

Barry wanted to do sth about Plapack. He found some bugs. I don't know
details. Of course, if I find some bugs in Petsc, I will report it. I
benefit a lot from it. thank you for your work in Petsc :).

Regards,
Yujie

On Mon, Sep 22, 2008 at 7:29 PM, Matthew Knepley <knepley at gmail.com> wrote:

> On Mon, Sep 22, 2008 at 9:43 PM, Lisandro Dalcin <dalcinl at gmail.com>
> wrote:
> > On Mon, Sep 22, 2008 at 11:03 PM, Yujie <recrusader at gmail.com> wrote:
> >> Dear Lisandro:
> >>
> >> Barry has tried to establish an interface for Plapack. However, there
> are
> >> some bugs in Plapack. Therefore, it doesn't work.
> >
> > Sorry, I didn't know about those Plapack issues.
>
> Neither did I, and seeing as how I use it, this is interesting. Please
> please please
> report any bugs you find, because I have been using it without problems.
>
>   Matt
>
> >> I am wondering if CG in
> >> Petsc can work with parallel dense matrix.
> >
> > Of course it works. In fact, any other KSP should work. As Barry said,
> > The KSP methods are INDEPENDENT of the matrix format, try -pc_type
> > jacobi as preconditioner.
> >
> >> When using the same matrix, which
> >> one is faster, sequential or parallel? thanks.
> >
> > For a fixed-size matrix, you should get really good speedups iterating
> > in parallel. Of course, that would be even better if you can generate
> > the local rows of the matrix in each processor. If not, communicating
> > the matrix row from the 'master' to the 'slaves' could be a real
> > bootleneck (large data to compute at the master while slaves waiting,
> > large data to scatter from master to slaves), If you cannot avoid
> > dense matrices, then you should try hard to compute the local rows at
> > the owning processor.
> >
> >
> >>
> >> On Mon, Sep 22, 2008 at 6:51 PM, Lisandro Dalcin <dalcinl at gmail.com>
> wrote:
> >>>
> >>> Well, any iterative solver will actually work, but expect a really
> >>> poor scalability :-). I believe (never used dense matrices) that you
> >>> could use a direct method (PLAPACK?), but again, be prepared for long
> >>> running times if your problem is (even moderately) large.
> >>>
> >>> On Mon, Sep 22, 2008 at 10:35 PM, Yujie <recrusader at gmail.com> wrote:
> >>> > To my knowledge, PETsc doesn't provide parallel dense matrix-based
> >>> > solvers,
> >>> > such as for CG, GMRES and so on. If it is, how to deal with this
> >>> > problem?
> >>> > Thanks.
> >>> >
> >>> > Regards,
> >>> >
> >>> > Yujie
> >>> >
> >>>
> >>>
> >>>
> >>> --
> >>> Lisandro Dalcín
> >>> ---------------
> >>> Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
> >>> Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
> >>> Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
> >>> PTLC - Güemes 3450, (3000) Santa Fe, Argentina
> >>> Tel/Fax: +54-(0)342-451.1594
> >>>
> >>
> >>
> >
> >
> >
> > --
> > Lisandro Dalcín
> > ---------------
> > Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
> > Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
> > Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
> > PTLC - Güemes 3450, (3000) Santa Fe, Argentina
> > Tel/Fax: +54-(0)342-451.1594
> >
> >
>
>
>
> --
> What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which
> their experiments lead.
> -- Norbert Wiener
>
>
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