[petsc-users] algorithm to get pure real eigen valule for general eigenvalue problem(Non-hermitian type)

[Jose E. Roman]

El 14/04/2013, a las 19:51, Zhang Wei escribió:

> Hi!
> Thanks for your reply. I am now dealing with non symmetric  eigen problem, where I expect to get these complex pairs. I am looking for the largest magnitude eigen pairs. But I always get many pure real eigen pairs,which in my case make no sense. The thing is that these are not totally wrong.since it is a standard case I compared with others, these real eigen values are somehow close to the magnitude of "correct" results.for eigen vectors, the "correct" results can be express as "T*exp(kx)",where the T is chebyshev polynomial. And all real eigen vectors I got are extract chebyshev polynomial. Actually I already set the problem to NHEP,and can get some complex eigen pairs. Comparing with expected one those eigen values are larger in angle. On the other hand I set the tolerance to 1e-9.
> 
> Thanks in advance!
> 

Are you completely sure that your matrix is being formed correctly? I would suggest running a small example with -mat_view_matlab then load the matrix and try eigs(A) in Matlab to make sure you get the expected results.

Jose