[petsc-dev] attaching field information to PetscLayout?

[Dmitry Karpeev]

On Sat, May 14, 2011 at 3:25 PM, Jed Brown <jed at 59a2.org> wrote:
> On Sat, May 14, 2011 at 22:21, Barry Smith <bsmith at mcs.anl.gov> wrote:
>>
>> The user will be composing preconditioners on splits etc using the string
>> name (you cannot type an IS at the command line but you can type "pressure")
>> so I am not sure why you are so focused on "the IS _is_ the thing you need".
>> So I can see the string names as being important.
>
> I assumed fieldsplit would use the string name and then hold onto the IS
> (there is a good chance it is needed internally anyway). I don't see why the
> string name would be needed in a performance-sensitive place since it's only
> for "configuration" anyway.
So the splits are identified by the IS (e.g., "give me the subvec
corresponding to the split with this IS")?
I assume that will require IS matching.  Is that faster than string
matching (I guess it depends on the string/IS length/type).

Dmitry.