[petsc-users] Lumped matrix

[Jed Brown]

Eric Chamberland <Eric.Chamberland at giref.ulaval.ca> writes:

> Hi,
>
> We are asking ourselves what would be the most efficient way to 
> create/do assembly/solve a problem involving a lumped matrix in PETSC?

Lumping frequently comes from reduced quadrature, so you could simply
use the reduced quadrature.  Lumping in a solver often comes from
computing row sums instead of the diagonal for Jacobi
smoothers/preconditioners.  In that case, just -pc_jacobi_type rowsum.

> #1- To create the matrix: Use an standard AIJ with 1 nnz per line 
> (didn't find any lumped or diagonal type)?

Right, or assemble the normal matrix and use Jacobi as above.
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