On 11/6/25 12:08, Arthur Bawin wrote:
present_pressure_values is part of the scratch_data, so I don't think this is
the issue. The attached gdb backtrace shows VecGetSize_Seq on top, called
in dealii::PETScWrappers::VectorBase::extract_subvector_to<unsigned int
const*, double*> , which would be a read issue on Petsc's end? (Sorry, I
should have included the backtrace in the first place).
Yes, I think my expectation would also have been that reading the size of a
vector via VecGetSize is thread-safe. Apparently, it is not :-( The function
is implemented here:
https://gitlab.com/petsc/petsc/-/blob/main/src/vec/vec/impls/seq/bvec2.c?ref_type=heads#L122
I can't really say why that would not be thread-safe: The only thing I can
imagine is the call to PetscFunctionBegin.
I do not know how to fix this, but here are a few suggestions:
* When you're in a debugger, take a look where the other threads are. In the
backtrace, one is clearly in a PETSc function. Check where the other thread
is, to make sure that you can narrow down that it's really concurrent access
to PETSc data that are the problem.
* If you have the ability, compile PETSc with debug flags so that you can go
in the debugger and check which line in the PETSc functions actually causes
the problem.
* Talk to the PETSc folks on their mailing list about the issue once you're
sure you know what the problem is.
I acknowledge that none of these options actually solve your problem.
Best
W.
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Wolfgang Bangerth email: [email protected]
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