I wanted to give you some info on your original question in case your
want to still use PETSc.
> It appears that for petsc, the assumption that the locally owned dofs Index
> Sets are contiguous is really throwing a wrench in our plans for the non
> block system approach. I have seen the other discussions where everyone
> says essentially it is not currently possible to get petsc and petsc
> wrappers to a point where it could use non contiguous locally owned index
> sets.
Yes, you need the locally owned range of indices to be contiguous.
This means, that you can split your matrices/vectors into blocks
however you want (for example by component), but they need to be
contiguous within a block.
> fe_values.get_function_values() on the velocity vector.
> ExcIndexNotPresent (n)
get_function_values() needs to see the ghost values of your vector
(all DoFs on a cell).
> So, in this new case, what would be a good way to accomplish the desired
> result?
how about:
...
DoFRenumbering::hierarchical (dof_handler);
std::vector<unsigned int> velocity_dof_indices1;
std::vector<unsigned int> velocity_dof_indices2;
for each active cell:
get_dof_indices(...)
for (unsigned int i;i<n_local_dofs;}}i)
{
unsigned int component = fe.system_to_component_index(i).first;
if (component<dim) // velocity
velocity_dof_indices1.push_back(local_dof_indices[i]);
}
DoFRenumbering::component_wise(dof_handler);
for each active cell:
get_dof_indices(...)
for (unsigned int i;i<n_local_dofs;}}i)
{
unsigned int component = fe.system_to_component_index(i).first;
if (component<dim) // velocity
velocity_dof_indices2.push_back(local_dof_indices[i]);
}
Now you have a mapping between the two different numberings and you
can use that to convert solution vectors. Note that you probably only
want to consider locally owned DoFs and use a more efficient data
structure that actually maps between the pairs of indices directly.
--
Timo Heister
http://www.math.clemson.edu/~heister/
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