Hi everyone,

I am having trouble with using SNES from petsc4py in PETSc 3.22. The problem is similar to https://gitlab.com/petsc/petsc/-/issues/1611 and related to the readonly access of “x”. Particularly, in my application, based on FEniCS, I want to solve a nonlinear PDE. Therefore, in my callbacks, I want to set the vector of DoFs of my FEniCS function to “x” with a line like

self.u.vector().vec().setArray(x)

However, this now raises the error

[0] Vector 'Vec_0x84000003_0' (argument #1) was locked for read-only access in unknown_function() at unknown file:0 (line numbers only accurate to function begin)

I believe that this is a consequence of https://gitlab.com/petsc/petsc/-/merge_requests/7567#22c226fc29b6fc9dc5781b0aff4dcc70ac6c3489, but I did not find any information on how to remove the lock from the vector or how I can set use “x” to update the vector of my function. Using

xx = x.getArray(readonly=True)

as described in https://gitlab.com/petsc/petsc/-/issues/1611 does not work either, as calling self.u.vector().vec().setArray(xx) then fails with the same error message.

Does anyone have an idea how to fix this?

Thanks a lot in advance,

Sebastian

--

Dr. Sebastian Blauth

Fraunhofer-Institut für

Techno- und Wirtschaftsmathematik ITWM

Abteilung Transportvorgänge

Fraunhofer-Platz 1, 67663 Kaiserslautern

Telefon: +49 631 31600-4968

sebastian.blauth@itwm.fraunhofer.de

https://www.itwm.fraunhofer.de