On 1/28/22 7:50 PM, Lucas Myers wrote:
**
Whoops, this one was indeed a silly error! The problem had nothing to do with
the `get_function_values` function. Rather, it only showed up there because
that is the only place that I use ghost elements. These weren't being updated
because (as clearly stated in the ghost vector documentation
<https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.dealii.org%2Fcurrent%2Fdoxygen%2Fdeal.II%2FDEALGlossary.html%23GlossGhostedVector&data=04%7C01%7CWolfgang.Bangerth%40colostate.edu%7C49474d9b216b42772e9608d9e2d21227%7Cafb58802ff7a4bb1ab21367ff2ecfc8b%7C0%7C0%7C637790215228308755%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=uxMqyURgOkHhJ3KNSOgZ1rdH3qgQyJQP2NtWkxOATjI%3D&reserved=0>)
one should not write to a ghosted vector, except by a copy assignment from a
completely distributed (non-ghost) vector. I fixed the problem by copying the
`locally_relevant_solution` vector into a `completely_distributed_solution`
vector, adding the update there, and then copying back over to the
`locally_relevant_solution` vector.
As an aside, is there a way to throw a warning/error if one tries to write to
a ghosted vector with anything except a completely distributed vector? If
possible, it might save someone some frustration...
Lucas -- I'm glad to hear you found the error. Reading through your email when
it came in first, I was thinking of exactly the situation you ultimately found
to be responsible: ghost values not properly updated.
As for the warning/error: Yes, there should ideally be one. Do you think you
can come up with as short a program that illustrates the mistake and that
should, but does not, produce an error? Then create a github issue that
documents this? Thanks in advance!
Best
W.
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Wolfgang Bangerth email: bange...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/
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