[petsc-users] SLEPc eigensolver that uses minimal memory and finds ALL eigenvalues of a real symmetric sparse matrix in reasonable time

[Shitij Bhargava]

Thank you Jed. That was indeed the problem. I installed a separate MPI for
PETSc/SLEPc, but was running my program with a default, already installed
one.

Now, I have a different question. What I want to do is this:

1. Only 1 process, say root, calculates the matrix in SeqAIJ format
2. Then root creates the EPS context, eps and initializes,sets parameters,
problem type,etc. properly
3. After this the root process broadcasts this eps object to other processes
4. I use EPSSolve to solve for eigenvalues (all process together in
cooperation resulting in memory distribution)
5. I get the results from root

is this possible ? I am not able to broadcast the EPS object, because it is
not an MPI_DataType. Is there any PETSc/SLEPc function for this ? I am
avoiding using MPIAIJ because that will mean making many changes in the
existing code, including the numerous write(*,*) statements (i would have to
convert them to PetscPrint in FORTRAN or something like that).
So I want a single process to handle matrix generation and assembly, but
want to solve the eigenproblem in parallel by different processes. Running
the subroutine EPSSolve in parallel and hence distribute memory is the only
reason why I want to use MPI.

Thanks a lot !!

Shitij

On 8 August 2011 11:05, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> On Mon, Aug 8, 2011 at 00:29, Shitij Bhargava <shitij.cse at gmail.com>wrote:
>
>> I* *ran it with:
>>
>> mpirun -np 2 ./slepcEigenMPI -eps_monitor
>>
>> I didnt do exactly what you said, because the matrix generation part in
>> the actual program is quite time consuming itself. But I assume what I am
>> doing is equivalent to what you meant to do? Also, I put MPD as
>> PETSC_DECIDE, because I didnt know what to put it for this matrix dimension.
>>
>> This is the output I get: (part of the output)
>> *MATRIX ASSMEBLY DONE !!!!!!!!
>>
>> MATRIX ASSMEBLY DONE !!!!!!!!
>>
>>   1 EPS nconv=98 first unconverged value (error) 1490.88 (1.73958730e-05)
>>   1 EPS nconv=98 first unconverged value (error) 1490.88 (1.73958730e-05)
>>   2 EPS nconv=282 first unconverged value (error) 3.04636e-27
>> (2.49532175e-04)
>>   2 EPS nconv=282 first unconverged value (error) 3.04636e-27
>> (2.49532175e-04)*
>
>
> The most likely case is that you have more than one MPI implementation
> installed and that you are running with a different implementation than you
> built with. Compare the outputs:
>
> $ ldd ./slepcEigenMPI
> $ which mpirun
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20110808/90580324/attachment.htm>