NewtonSolver in v11

dolfinx
1

Hello, I am trying to run the hyperelasticity demo from Hyperelasticity — Computational Mechanics Numerical Tours with FEniCSx , but I get the following error message, related to NewtonSolver in NonlinearProblem:

Traceback (most recent call last):
  File "/home/claire/Downloads/hyperelasticity.py", line 224, in <module>
    solver = nls.petsc.NewtonSolver(mesh.comm, problem)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/claire/anaconda3/envs/fenicsx-env-v11/lib/python3.11/site-packages/dolfinx/nls/petsc.py", line 54, in __init__
    self._A = create_matrix(problem.a)
                            ^^^^^^^^^
AttributeError: 'NonlinearProblem' object has no attribute 'a'. Did you mean: 'A'?
Exception ignored in: <function NewtonSolver.__del__ at 0x7fc392df0720>
Traceback (most recent call last):
  File "/home/claire/anaconda3/envs/fenicsx-env-v11/lib/python3.11/site-packages/dolfinx/nls/petsc.py", line 62, in __del__
    for obj in filter(lambda obj: obj is not None, (self._A, self._b)):
                                                    ^^^^^^^
AttributeError: 'NewtonSolver' object has no attribute '_A'

I am not sure how to solve this. I have already tried editing lines below line 210:

petsc_options = {
    "snes_type": "newtonls",
    "snes_linesearch_type": "none",
    "snes_stol": np.sqrt(np.finfo(dolfinx.default_real_type).eps) * 1e-2,
    "snes_atol": 0,
    "snes_rtol": 0,
    "ksp_type": "preonly",
    "pc_type": "lu",
    "pc_factor_mat_solver_type": "mumps",
    "snes_monitor": None,
}
problem = fem.petsc.NonlinearProblem(Residual, u, bcs=bcs,  petsc_options_prefix="demo_hyperelasticity_",  petsc_options=petsc_options)

but I still get the error above.

Many thanks in advance for your help !

Kind regards,

Claire

2

As far as what i know, the referenced hyperelasticity demo corresonding to dolfinx version 0.8. For version V11 it might not be compatible, which is why the possible error.

From the small snippet, i noticed that you have to replace the definition of problem as,

from dolfinx.fem.petsc import NewtonSolverNonlinearProblem
problem = fem.petsc.NewtonSolverNonlinearProblem(Residual, u, bcs,)
solver = nls.petsc.NewtonSolver(mesh.comm, problem)

Also when i tried, there is another modification subjected to v11,

# u.vector.set(0.0) --> to be replaced as 
u.x.petsc_vec.set(0.0)

I hope this works.