[petsc-users] Eigenvalues calculations in PETSc

[Qin Lu]

Hello,

I need to find the spectrum of the a large linear system (over 100,000 unknowns). Option -ksp_compute_eigenvalues_explicitly ran out of memory since the matrix is too big, then -ksp_compute_eigenvalues only gave a small number of eigenvalues (around 30). My questions are:

1. Is the number of computed eigenvalues determined by the number of GMRES iterations to converge?
2. Can PETSc give the extreme eigenvalues now that the number of computed eigenvalues is limited?

Thanks a lot for your info,
Qin