[petsc-users] SLEPc: logpcg works but lanczos fails

[Qiyue Lu]

Hello,
I am solving a general eigenvalue problem
Ax=lamda*Bx
A is the stiffness matrix, B the mass matrix. The DOF of these matrices are
24,000 around. Both of them are symmetric and stored in SEQSBAIJ format.
Also, I downloaded mumps during the configuration and installation of
PETSc.
In SLETc, this eigenvalue system can be solved by *-eps_tpye logpcg* while
requesting *EPS_SMALLEST_REAL*. However, *-eps_type lanczos* doesn't work,
which yields a very huge number. It seems mumps is called indeed. The
output of *-eps_view* is attached. The command line I am using is:
*mpirun -np 40 ./test -fA matrixA -fB matrixB -eps_type lanczos -eps_view*

Did I miss any substantial configurations for lanczos solver?

Thanks,

Qiyue Lu
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