[petsc-dev] FieldSplit restrictions

[Barry Smith]

On May 15, 2010, at 5:09 PM, Jed Brown wrote:

> Is there a case for putting a field in more than one split?  

    I believe absolutely. It is like overlapping Schwarz but not with overlapping grid points instead overlapping components.

    Barry

> The current
> implementation allows this, but it makes it easier to accidentally have
> more splits than you wanted.  The underlying challenge for Doing the
> Right Thing is that the type is not normally set until
> PCSetFromOptions().  Any calls to PCFieldSplitSet* will be ignored prior
> to this.  The problem occurs when the user specifies
> -pc_fieldsplit_*_fields AND the code adds splits with
> PCFieldSplitSet(IS|Fields).  This used to create a bunch of splits which
> is probably not what anyone asked for, I just pushed a some code that
> makes command-line split definitions permanent.  This isn't entirely
> satisfactory because there isn't currently a way to get rid of them, but
> it's better than having lots of spurious splits.
> 
> Lisandro, let me know if the current code behaves the way you expect.
> 
> Jed