[petsc-users] left and right preconditioning with a constant null space

[Klaij, Christiaan]

I'm solving the Navier-Stokes equations using PCFieldSplit type
Schur and Selfp. This particular case has only Neumann conditions
for the pressure field.

With left preconditioning and no nullspace, I see that the KSP
solver for S does not converge (attachment "left_nonullsp") in
either norm.

When I attach the constant null space to A11, it gets passed on
to S and the KSP solver for S does converge in the preconditioned
norm only (attachment "left").

However, right preconditioning uses the unpreconditioned norm and
therefore doesn't converge (attachment "right"), regardless of
whether the nullspace is attached or not. Should I conclude that
right preconditioning cannot be used in combination with a null
space?

Chris


dr. ir. Christiaan Klaij  | Senior Researcher | Research & Development
MARIN | T +31 317 49 33 44 | mailto:C.Klaij at marin.nl | http://www.marin.nl

MARIN news: http://www.marin.nl/web/News/News-items/H2020-marinergi-project-launched.htm

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