[petsc-users] Questions about TS
Blaise Bourdin
bourdin at math.lsu.edu
Wed Oct 19 10:54:13 CDT 2011
Hi,
I am trying to use TS to solve a simple transient problem in an unstructured finite element f90 code.
1. Section 6.1.1 of the manual refers to a TSSetMatrices function that can be used to set the RHS and LHS matrices, but I can;t find it. Is this section outdated?
2. Since we are using unstructured finite elements, the LHS matrix is not the identity. As far as I understand, we have two possible choices:
- Use a mass lumping approximation of the variational identity matrix (mass matrix), M, and use M^{-1}K for the RHS matrix instead of K.
- Use an IMEX method where the implicit matrix is the variational identity M.
Is this right? What is the recommended way?
3. Is src/ts/examples/tests/ex1f.F supposed to work? Is there a fortran or fortran90 example I could start from? I get the following:
galerkin:tests bourdin$ ./ex1f -linear_constant_matrix
1 Procs Avg. error 2 norm NaN NaN euler
galerkin:tests bourdin$ ./ex1f
1 Procs Avg. error 2 norm NaN NaN euler
Thanks,
Blaise
--
Department of Mathematics and Center for Computation & Technology
Louisiana State University, Baton Rouge, LA 70803, USA
Tel. +1 (225) 578 1612, Fax +1 (225) 578 4276 http://www.math.lsu.edu/~bourdin
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