[petsc-users] Slepc: Nonlinear eigenvalue problem

[Manav Bhatia]

Thanks for the clarification. 

Does this also apply to the standard non-hermitian eigenvalue problem? Do I need to compile with complex numbers if I want to capture the complex eigenvalues? Or does it work with real number support? 

Thanks
Manav

Sent from my iPhone

> On Oct 23, 2018, at 3:43 AM, Jose E. Roman <jroman at dsic.upv.es> wrote:
> 
> If eigenvalues are complex then NLEIGS also needs to work in complex arithmetic because it needs a region of the complex plane containing the wanted eigenvalues. It seems that complex arithmetic is the only change in your problem.
> 
> Jose
> 
> 
>> El 22 oct 2018, a las 22:01, Manav Bhatia <bhatiamanav at gmail.com> escribió:
>> 
>> Thanks, Jose. 
>> 
>> How difficult would it be to add the support for the general case (if at all possible)? 
>> 
>> My eigenvalue problem is of the form shown in the attachment. Beta is the eigenvalue and X_s^\Delta is the eigenvector. While some of the matrices are known, others are defined only as matrix vector products. 
>> 
>> I am interested in eigenvalues with the largest real part. I expect to find complex eigenvalues, although for a small subset of cases these will be real. 
>> 
>> What is your recommendation for attacking this problem with the nonlinear eigenvalue support in Slepc? 
>> 
>> Would appreciate your guidance. 
>> 
>> Regards,
>> Manav
>> 
>> <PastedGraphic-1.pdf>
>> 
>> 
>>> On Oct 22, 2018, at 2:40 PM, Jose E. Roman <jroman at dsic.upv.es> wrote:
>>> 
>>> 
>>> 
>>>> El 22 oct 2018, a las 21:05, Manav Bhatia <bhatiamanav at gmail.com> escribió:
>>>> 
>>>> Hi, 
>>>> 
>>>> I am exploring the nonlinear eigenvalue problem solver in Slepc. 
>>>> 
>>>> From the notes in "Sec 6.4: Retrieving the Solution”, it appears that if I expect to find complex eigenpairs then I must compile the library (and Petsc) with complex scalars. Is that correct? 
>>>> 
>>>> Is there a way to include support for complex eigenpairs in a library complied with real scalars? 
>>>> 
>>>> Regards,
>>>> Manav
>>>> 
>>>> 
>>> 
>>> Currently, the only combination that supports complex eigenpairs with real scalars is the split form for the nonlinear function with the NLEIGS solver.
>>> 
>>> Jose
>> 
>