[petsc-users] Questions about TS

[Blaise Bourdin]

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 Is this section outdated?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 

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Department of Mathematics and Center for Computation & Technology
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