[petsc-dev] Fwd: rename SNES methods ls, tr etc

[Jed Brown]

On Wed, Dec 5, 2012 at 10:36 AM, Anton Popov <popov at uni-mainz.de> wrote:

> This is not exactly clear to me. Residuals for Dirichlet DOF should be
> (set to) zero, should they? Because those are not unknowns. What do you
> mean by Dirichlet boundary residuals?


If you leave the variables in the vector (convenient for visualization, for
example) then you have to write residuals for them. With most
preconditioners, those residuals will be zero after the first iteration,
but that is not required.


> Is there any SNES example demonstrating usage of Newton or Picard for a
> problem with non-zero Dirichlet BC?


The lid-driven cavity examples do the non-symmetric version. snes ex48 uses
symmetric version enforcement and could trivially be inhomogeneous. When
working with external applications, I almost always advocate doing this
instead of removal or other ad-hoc boundary condition implementations.

Here is a slightly more formal explanation:

http://scicomp.stackexchange.com/a/3300/119
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