[petsc-dev] I don't understand PETSCPARTITIONSHELL

[Matthew Knepley]

On Thu, Feb 9, 2017 at 9:51 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
>   So shell can 1) use some random partitioner or 2) allow the user to
> provide the partitioning?
>
>   This is a strange combination. Won't it be better to have
> PETSCPARTIONERRANDOM and PETSCPARTITIONERSHELL?
>
>   You could use the random for the tests (but as command line options not
> hardwired in the examples).


Oh God. Yes, I forgot that was in there. We can move it to Simple, where it
makes sense.

  Matt


>
>    Barry
>
>
> > On Feb 9, 2017, at 9:45 PM, Matthew Knepley <knepley at gmail.com> wrote:
> >
> > On Thu, Feb 9, 2017 at 9:36 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> >
> >   Matt,
> >
> >    I don't understand PETSCPARTITIONSHELL.
> >
> >    Why does it exist? Why not just use PETSCPARTITIONSIMPLE when no
> other partitioner exists?
> >
> >    Why is it called shell? Other XXSHELL allow users to provide their
> own routines to provide the XX functionality, this does not seem to do
> that. So it is not shell in the PETSc sense.
> >
> >    Why hard wire examples to use it? Why not just have list it as an
> args: in the test cases with -petscpartitioner_type shell (but why not just
> simple?) putting the ugly shit directly into the source code seems
> unnecessary and annoying.
> >
> > 1) The two partitioners do different things:
> >
> >   Simple: It divides the cells evenly without reordering.
> >
> >   Shell: It allows the user to set a prescribed partition
> >
> > It is clear to me that Shell is needed because sometimes you want to
> prescribe the partition, if for no
> > other reason than you know that a certain partition has a bug. Simple is
> questionable, but we were
> > using it for testing.
> >
> > 2) It is called Shell because for a shell the user prescribes the
> behavior directly, which is exactly what happens.
> >
> > 3) I did not put it in arguments because it can get very long, and I
> thought it was easier to see and manipulate in the code. I am open to
> moving it.
> >
> >   Matt
> >
> >
> >
> >   Barry
> >
> >
> >
> >
> >
> >
> > --
> > What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which their
> experiments lead.
> > -- Norbert Wiener
>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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