Converting from TDofs to LDofs

[j-signorelli]

Hi,

I have the following code I have written for converting tdofs to ldofs:

void TDofToLDof(const FiniteElementSpace &f, const Array<int> &tdof_indices, Array<int> &ldof_indices)
{
    Array<int> tdof_marked, ldof_marked;

    f.ListToMarker(tdof_indices, f.GetTrueVSize(), tdof_marked, 1);

    const SparseMatrix *P = f.GetConformingProlongation();

    if (!P)
    {
        ldof_marked.MakeRef(tdof_marked);
    }
    else
    {
        
        P->BooleanMult(tdof_marked, ldof_marked);
    }

    f.MarkerToList(ldof_marked, ldof_indices);
}

This works when I run with 1 MPI proc; however, when I use >1 MPI procs, this code fails. To my understanding based on the MFEM website/documentation, $P$ should be generally be instantiated when using >1 processor, but it is not. I believe that this is why this code is failing, but am not sure why $P$ isn't being instantiated in the first place (unless I am misunderstanding something more fundamental).

Any assistance with this is greatly appreciated, thank you!

[j-signorelli]

Working code:

void TDofToLDof(const ParFiniteElementSpace &f, const Array<int> &tdof_indices, Array<int> &ldof_indices)
{
    Array<int> tdof_marked, ldof_marked;

    ldof_marked.SetSize(f.GetVSize());

    f.ListToMarker(tdof_indices, f.GetTrueVSize(), tdof_marked, 1);

    const SparseMatrix *Rt = f.GetRestrictionMatrix();
    Rt->BooleanMultTranspose(tdof_marked,ldof_marked);

    f.MarkerToList(ldof_marked, ldof_indices);
}