PCNN preconditioner and setting the interface

[Andreas Grassl]

Hello,

I'm working with a FE-Software where I get out the element stiffness
matrices and the element-node correspondency to setup the stiffness
matrix for solving with PETSc.

I'm currently fighting with the interface definition. My
LocalToGlobalMapping for test-purposes was the "identity"-IS, but I
guess this is far from the optimum, because nowhere is defined a node
set of interface nodes.

How do I declare the interface? Is it simply a reordering of the nodes,
the inner nodes are numbered first and the interface nodes last?

Thank you in advance

ando

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