[petsc-dev] Discussion about time-dependent optimization moved from PR

[Jed Brown]

Lawrence Mitchell <wencel at gmail.com> writes:

>> On 16 Oct 2017, at 09:35, Stefano Zampini <stefano.zampini at gmail.com> wrote:
>> 
>> Jed,
>> 
>> have you thought about how to fix this?
>> 
>> https://lists.mcs.anl.gov/pipermail/petsc-dev/2017-October/021387.html

I feel like I'm missing context.  I know I failed to follow up in a
thread at some time in the past, but I don't really understand the
problem or what is being attempted.  What is the failing test case?

> c.f. also the petsc-maint discussion last October in the thread:
>
> "Segfault when DM is reused in two SNESes with multigrid"

What should I do?  That thread petered out when nobody could suggest a
criteria to distinguish reuse of a DM in related SNES objects (e.g.,
nonlinear preconditioning or nonlinear multigrid) from reuse with intent
to solve different problems.

When I suggested as a young child that DM be essentially just a function
space and create a new object for resolution-independent specification
of a problem (residual and Jacobian functions and related components),
Barry wanted it to be part of DM to avoid having a new object.  So it's
part of DM -- make a new DM if you're solving a different problem.