[petsc-users] DMPlexMatSetClosure for non connected points in DM

[Ashish Patel]

Dear PETSc users,

I am trying to assemble a matrix for a finite element problem where the
degree of freedom (dof) on a surface is constrained via a reference node
which also exists in the DM but is not connected  with any other point in
the mesh. To apply the constraint I want to be able to set matrix values in
the rows belonging to dofs of reference nodes and columns belonging to dofs
of surface nodes and vice versa. But since the two points are not connected
topologically I cannot just use DMPlexMatSetClosure to do that. I am
currently trying to use DMPlexAddConeSize on all the constrained surface
points followed by a call to DMPlexInsertCone wherein I add the reference
node to the cone of surface point before setting up the PetscSection. Is
this the right approach? I am currently getting following message

New nonzero at (8952,28311) caused a malloc
Use MatSetOption(A, MAT_NEW_NONZERO_ALLOCATION_ERR, PETSC_FALSE) to turn
off this check

I could set the suggested option to get rid of the error but was wondering
if I am missing something.

Thanks
Ashish
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