[petsc-users] Need to update matrix in every loop

[sheng liu]

Thank you very much! I have another question. If I need all the eigenvalues
of the sparse matrix, which solver should I use? Thanks!

2015-08-09 1:52 GMT+08:00 Barry Smith <bsmith at mcs.anl.gov>:

>
> > On Aug 8, 2015, at 7:52 AM, sheng liu <ustc.liu at gmail.com> wrote:
> >
> > Hello:
> >     I have a large sparse symmetric matrix ( about 1000000x1000000), and
> I need about 10 eigenvalues near 0. The problem is: I need to run the same
> program about 1000 times, each time I need to change the diagonal matrix
> elements ( and they are generated randomly). Is there a fast way to
> implement this problem? Thank you!
>
>   Does each run depend on the previous one or are they all independent?
>
>   If they are independent I would introduce two levels of parallelism: On
> the outer level have different MPI communicators compute different random
> diagonal perturbations and on the inner level use a small amount of
> parallelism for each eigenvalue solve. The outer level of parallelism is
> embarrassingly parallel.
>
>   Of course, for runs of the eigensolve use -log_summary to make sure it
> is running efficiently and tune the amount of parallelism in the eigensolve
> for best performance.
>
>    Barry
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20150812/fb533ee4/attachment.html>