[petsc-users] SLEPC matrix Query

[Matthew Knepley]

On Wed, Apr 25, 2018 at 8:10 AM, Savneet Kaur <Savneet.KAUR at cea.fr> wrote:

> Hello Again,
>
> Yes I would like to find for the initial 10% and 20% of the eigenpairs.
> But in addition to this,I also want to check for the full spectrum.
>
> So, how shall I proceed with it?
>
First just setup the eigensolve. I don't think anything you are asking for
is missing from the standard interface.

Checking the full spectrum is only possible with small matrices. SLEPc
would just interface to LAPACK for that.

  Thanks,

    Matt

Thank You.
>
> Regards,
> savneet
>
> Le 25/04/2018 à 11:33, Matthew Knepley a écrit :
>
> On Wed, Apr 25, 2018 at 5:10 AM, Savneet Kaur <Savneet.KAUR at cea.fr> wrote:
>
>> Hello,
>>
>> Warm Regards
>>
>> I am Savneet Kaur, a master student at University Paris Saclay and
>> currently pursuing an internship at CEA Saclay (France).
>>
>> I have recently started to understand the slepc and petsc solvers, by
>> taking up the tutorials for eigenvalue problems. In my internship work I
>> have to develop a laplacian matrix from a given transition rate matrix and
>> solve it using SLEPC and PETSC and to evaluate the lowest eigenvalue.
>>
>> I was wondering if I could get some information. I need to diagonalize a
>> 2D Laplacian matrix. And writing a code in C and diagonalizing it is easy.
>> But I am not getting it how to accommodate with the SLEPC Program. Am i
>> suppose to use any packages or it will is done by a loop? Or I need to read
>> some other manual to understand how does it work. Please kindly let me know.
>>
> I would just like to clarify some terminology. "Diagonalize" would usually
> mean find all eigenvalues and eigenvectors.
> Is this what you mean? Often, SLEPc users want only a portion of the
> spectrum since the matrices are enormous.
>
>   Thanks,
>
>      Matt
>
>> The diagonalizing a matrix will be preliminary step of my work.
>>
>> I will be highly obliged to the the team, if I could get help.
>>
>> Hoping for a favorable response from your side.
>>
>> Thank you for the time and consideration.
>>
>>
>> Sincerely,
>>
>> *Savneet Kaur*
>>
>> *Intern at DEN/DANS/DMN/SRMP*
>>
>>
>> *CEA - Centre de Saclay ǀ Bâtiment 520 *
>>
>> *91191 Gif-sur-Yvette Cedex*
>>
>> *France*
>>
>> *Tel: +33 (0) 666 749 000*
>>
>>
>> *Email: savneet.kaur at cea.fr <savneet.kaur at cea.fr> *
>>
>>
>>
>>
>
>
> --
> 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
>
> https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/%7Emk51/>
>
>
>


-- 
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

https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/>
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