[petsc-users] Solving eigenproblems in the form of Stokes equations
Julian Andrej
juan at tf.uni-kiel.de
Fri Jul 10 16:28:24 CDT 2015
Hi,
i'm trying to solve a generalized eigenvalue problem which is the
stokes equations discretized by finite elements (with fenics) and
producing a banded matrix (reordered structure) of the well known
block form
[N Q]
[QT 0]
The domain is the unit square with dirichlet boundary condition
evaluating to zero at all boundary nodes.
A is the block matrix in banded reordered structure and M is the mass matrix.
I'm using slepc4py for the eigenvalue calculation.
E = SLEPc.EPS().create()
E.setOperators(A, M)
E.setDimensions(NEV, PETSc.DECIDE)
E.setFromOptions()
I always get the error
[0] Zero pivot row 1 value 0 tolerance 2.22045e-14
I cannot find a combination which solves the eigenvalues for this problem.
The system itself solves fine with a KSP solver object from PETSc
using tfmqr with the icc PC.
I can assemble the matrix with a penalty term for the pressure and
calculate the eigenvalues with a direct solver, but i try to avoid
that.
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