[petsc-users] SLEPc/NEP for shell matrice T(lambda) and T'(lambda)

[Kenneth C Hall]

Hi all,

I have a very large eigenvalue problem of the form T(\lambda).x = 0. The eigenvalues appear in a complicated way, and I must use a matrix-free approach to compute the products T.x and T’.x.

I am trying to implement in SLEPc/NEP.  To get started, I have defined a much smaller and simpler system of the form
A.x - \lambda x = 0 where A is a 10x10 matrix. This is of course a simple standard eigenvalue problem, but I am using it as a surrogate to understand how to use NEP.

I have set the problem up using shell matrices (as that is my ultimate goal).  The full code is attached, but here is a smaller snippet of code:


!.... Create matrix-free operators for A and B

      PetscCall(MatCreateShell(PETSC_COMM_SELF,n,n,PETSC_DETERMINE,PETSC_DETERMINE, PETSC_NULL_INTEGER, A, ierr))

      PetscCall(MatCreateShell(PETSC_COMM_SELF,n,n,PETSC_DETERMINE,PETSC_DETERMINE, PETSC_NULL_INTEGER, B, ierr))

      PetscCall(MatShellSetOperation(A, MATOP_MULT, MatMult_A, ierr))

      PetscCall(MatShellSetOperation(B, MATOP_MULT, MatMult_B, ierr))



!.... Create nonlinear eigensolver

      PetscCall(NEPCreate(PETSC_COMM_SELF, nep, ierr))



!.... Set the problem type

      PetscCall(NEPSetProblemType(nep, NEP_GENERAL, ierr))

!

!.... set the solver type

      PetscCall(NEPSetType(nep, NEPNLEIGS, ierr))

!

!.... Set functions and Jacobians for NEP

      PetscCall(NEPSetFunction(nep, A, A, MyNEPFunction, PETSC_NULL_INTEGER, ierr))

      PetscCall(NEPSetJacobian(nep, B,    MyNEPJacobian, PETSC_NULL_INTEGER, ierr))

The code runs, calls MyNEPFunction and MatMult_A multiple times, sweeping over the prescribed RG range, but crashes before it ever calls MyNEPJacobian or MatMult_B.  The NEP viewer and error messages are attached.

Any help on getting this problem properly set up would be greatly appreciated.

Kenneth Hall
ATTACHMENTS:
test_nep.f90
code_output

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