[petsc-dev] FieldSplit restrictions

[Jed Brown]

On Sat, 15 May 2010 22:19:09 -0500, Matthew Knepley <knepley at gmail.com> wrote:
> I agree with Barry.
> 
> By "making command line splits permanent" you mean they are not overridden
> by API splits?

What I have right now is that if you create splits with
-pc_fieldsplit_*_fields, any subsequent API splits are ignored.  I don't
like this, but the alternatives are to ignore the command line or to
take both.  The old behavior was to take both, but then you would
commonly get lots of splits with likely unexpected prefixes.  Now that
API splits are named, they at least have predictable names.  But I would
expect it is much more common to create command-line splits *instead of*
the API splits rather than in addition to.  The trouble is that it's not
possible to set API splits until after PCSetFromOptions(), so the
command-line splits will already exist.  I'd appreciate suggestions on
semantics (what should be set when, and how forcefully).

Jed