about KSP based on parallel dense matrix

[Richard Tran Mills]

Matt,

I use it too.  Last time I checked, though, it seemed to be broken in 
petsc-dev: I could no longer build it using --download-plapack with 
configure.py.  (I think the problem is that no one finished migrating it to 
the new direct solver interface -- I haven't had time to investigate, though.)

It was working for me in 2.3.3, though.  I assume Yujie is using the release 
version of PETSc?

--Richard

Matthew Knepley 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
>>
>>
> 
> 
>