[petsc-users] EPSSolve does not converge for a few eigenvalues of large-scale matrix

[Gao Bin]

Hi, all

I am trying to solve a few eigenvalues in a interval of a sparse Hermitian matrix (F) with the dimension as 2362. I know there are only 20 eigenvalues in the interval [-80.0,-70.0] for the matrix F. I choose the EPSARNOLDI method. The code looks like as follows. But after several hours running, EPS can not get converged eigenvalues. Therefore, may I ask if I did some wrong in the code? Or should I add more solver parameters for my problem? Thank you in advance.

#include <finclude/slepcepsdef.h>
      use slepceps
#if defined(PETSC_USE_FORTRAN_DATATYPES)
      type(Mat) F
      type(EPS) solver
#else
      Mat F
      EPS solver
#endif
      ... ...
      ! creates eigensolver context
      call EPSCreate(PETSC_COMM_WORLD, solver, ierr)
      ! sets operators
      call EPSSetOperators(solver, F, PETSC_NULL_OBJECT, ierr)
      ! sets solver parameters
      call EPSSetProblemType(solver, EPS_HEP, ierr)
      call EPSSetWhichEigenpairs(solver, EPS_ALL, ierr)
      call EPSSetInterval(solver, -80.0, 70.0, ierr)
      call EPSSetType(solver, EPSARNOLDI, ierr)
      call EPSSetTolerances(solver, 1.0D-9, 90000, ierr)
      ! solve the eigensystem
      call EPSSolve(solver, ierr)

Cheers

Gao
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