[petsc-users] Repeated global indices in local maps

[Prateek Gupta]

Hi,
I am new to using petsc and need its nonlinear solvers for my code. I am
currently using parmetis (outside petsc) to partition an unstructured mesh
element-wise, but working with data on the vertices of the mesh.
Consequently, I have repeated vertices in different MPI-processes/ranks. At
the solver stage, I need to solve for the data on vertices (solution vector
is defined on the vertices). So, I need to create a distributed vector over
vertices of the mesh, but the distribution in MPI-ranks is not contiguous
since partitioning is (has to be) done element wise. I am trying to figure
out,
1. if I need only Local to Global IS or do I need to combine them with AO?
2. Even at the VecCreateMPI stage, is it possible to inform petsc that,
although, say, rank_i has n_i components of the vector, but those
components are not arranged contiguously?

For instance,

Global vertices vector v : [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
v_rank_1 : [2, 3, 4, 8, 9, 7] ; v_rank_2 : [0, 1, 2, 3, 6, 10, 11, 8, 9, 5]



Any help is greatly appreciated.

Thank you.
Prateek Gupta
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