about KSP based on parallel dense matrix

[Lisandro Dalcin]

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.

> 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