[Trilinos-Users] Tpetra::Vbr results for 1x1 block not matching Tpetra::Crs

C.S. Natarajan csnataraj at gmail.com
Sun Oct 27 19:03:34 MDT 2013

Hello All,
        I have a question concerning the Tpetra::VbrMatrix interface. For
1x1 blocks I would think that the Tpetra/Epetra Crs interface and the
Tpetra Vbr interface should produce identical results. However, I am seeing
that this is not the case. I am wondering if I am abusing the interface or
just doing something blatantly wrong. I am attaching a code below that
generates the FEM system ( with Q1 elements) for 2D (vanilla-) Poisson in
parallel. The Tpetra::Vbr interface doesn't produce the same results (as in
correct) as the crs interface in epetra/tpetra.  (The stencil should be 9
nnz's per interior point--not adjacent to boundary; with 8/3 diagonal and
-1/3 off diagonal). The correct values are being passed for insertion,
however, it looks like there is some issue during the summation from
off-processor elements. The epetra/Tpetra crs matrices and the Tpetra Vbr
Matrix all have their values inserted into identical row and column indices.

I would appreciate any input.

Thanks and best,
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