[petsc-users] want some explanations on BC setup

Jed Brown jed at 59A2.org
Fri Apr 23 11:19:56 CDT 2010

On Fri, 23 Apr 2010 16:01:21 +0000, "Li, Zhisong (lizs)" <lizs at mail.uc.edu> wrote:
> 1. Direct removing temperature terms in snes/ex19.c doesn't give a
> sensible result except applying option "-snes_mf" or
> "-snes_mf_operator".

DMMG normally computes the operator using coloring which is essentially
the same operation as used for -snes_mf/-snes_mf_operator.  You haven't
given enough information to explain what's wrong.

> 2. Combining snes/ex19.c and ts/ex7.c (no temperature), I could not
> even get a converging SNES function norm or bounded result if I
> strictly follow your BC rules. But I can make it converged or bounded
> by setting BC like " f[j][i] = - lid " or "x[j][i] = - lid "
> with/without -snes_mf.

I don't believe you are actually doing this since it will not converge:
f[j][i] will never go to zero so the norm of the residual will not


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