[petsc-dev] Petsc "make test" have more failures for --with-openmp=1

[Matthew Knepley]

On Fri, Mar 19, 2021 at 2:21 PM Jed Brown <jed at jedbrown.org> wrote:

> Matthew Knepley <knepley at gmail.com> writes:
>
> >> Notice how the permutations are contained within the vertices {0, ...,
> 8},
> >> edges {9, ..., 24}, and cells {25, ..., 32}. I would like to get rid of
> >> that restriction, but you've said it would have significant non-local
> >> consequences so I haven't tried.
> >>
> >
> > Yes, that is not a good idea, even in theory. It wrecks the nice
> contiguity
> > we use for topological operations.
> >
> > As Lawrence points out, this need not affect your smoother because dof
> > permutations can break this stratification. It has been that way for a
> > decade.
>
> I only want to break dof stratification, not point stratification. The
> points produced by the stratified RCM are okay (at least as Lawrence
> described it; not sure how it's done in DMPlexGetOrdering, but can't be
> anything hard).
>
> What code needs to be written to get unstratified RCM-like dofs? Lawrence
> evidently has this code in Firedrake, but I want it in DMPlex, tested and
> probably done by default because most users would benefit from it. I could
> swear you said it would break some other assumptions and thus not
> everything would work, but perhaps we weren't talking about the same thing.
>

It is possible that I misunderstood what you were asking for. What Section
requires for everything to work is that dofs follow the point ordering. The
point
ordering can be anything we want since we can use a permutation from the
mesh point ordering. However, some stuff depends on all dofs associated with
a point being contiguous. Not everything does, since I wrote something for
LibMesh which allows them to order in a field major way, instead of point
major,
but it is probably not possible to individually permute unknowns. Usually,
this is not what we want anyway I would assume.

  Thanks,

     Matt

-- 
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

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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