[petsc-users] questions about PetscSF

[Fande Kong]

Jed,

Thanks,

I readed the node you gave. I still have some questions.

(1) One root can be related with zero, one or many leaves, right? One leaf
only can be related with zero or one root.

(2) In Algorithms section. Could you please give me a very simple example
to demonstrate how  'Extracting a submatrix from a sparse matrix', '
Ownership discovery and transfer' and 'Graph distribution'. The description
is hard for me to understand.

Fande,


On Mon, Mar 3, 2014 at 5:54 PM, Jed Brown <jed at jedbrown.org> wrote:

> Fande Kong <fd.kong at siat.ac.cn> writes:
>
> > Hi all,
> >
> > I was wondering mechanisms of the object PetscSF. What are definitions of
> > roots and leaves? Do roots/leaves associate with the data we want to
> > receive/send?  For the function Bcast, it seems that we transfer data
> from
> > roots to leaves. But in another function Reduce, it seems that we move
> data
> > in the opposite direction (from leaves to roots). These kind of
> mechanisms
> > possibly make users confused.
>
> The SF graph is asymmetric so that it can have cleaner semantics.  Read
> my note and reply here if something is still unclear.
>
> http://59a2.org/files/StarForest.pdf
>
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