[petsc-users] Trying to write Fortran version of ksp/ex34.c

[Åsmund Ervik]

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Dear PETSc users,

I'm trying to write a Poisson solver in Fortran using the
KSPSetComputeOperators etc. framework. When debugging this, I ended up
modifying ksp/ex22.f so that it matches ksp/ex34.c. The difference
between these is that ex34.c has a non-constant RHS and Neumann BCs,
which is closer to what I want.

Now, when I run these two programs I get the following:

./ex22f_mod
   Residual, L2 norm         1.007312
   Error, sup norm         0.020941
   Error, L1 norm        10.687882
   Error, L2 norm         0.340425

./ex34
   Residual, L2 norm 1.07124e-05
   Error, sup norm 0.0209405
   Error, L1 norm 0.00618512
   Error, L2 norm 0.000197005

but when I MatView/VecView the matrix and RHS for each example (write
them to file), there is no difference. I have attached ex22f_mod.F90,
any suggestions on what the error is?

Once this example works, you can of course include it with PETSc.

Regards,
Åsmund

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