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# Copyright (C) 2021-2025 Jørgen S. Dokken
#
# This file is part of DOLFINx (https://www.fenicsproject.org)
#
# SPDX-License-Identifier: LGPL-3.0-or-later
"""(Deprecated) Methods for solving nonlinear equations using PETSc
solvers."""
from __future__ import annotations
import typing
import warnings
from mpi4py import MPI
from petsc4py import PETSc
from dolfinx.fem.forms import extract_function_spaces
if typing.TYPE_CHECKING:
import dolfinx
assert dolfinx.has_petsc4py
from dolfinx.fem.petsc import NewtonSolverNonlinearProblem
import types
from dolfinx import cpp as _cpp
from dolfinx import fem
from dolfinx.fem.petsc import (
create_matrix,
create_vector,
)
__all__ = ["NewtonSolver"]
class NewtonSolver(_cpp.nls.petsc.NewtonSolver):
def __init__(self, comm: MPI.Intracomm, problem: NewtonSolverNonlinearProblem):
"""(Deprecated) A Newton solver for non-linear problems.
Note:
This class is deprecated in favour of
:class:`dolfinx.fem.petsc.NonlinearProblem`, a high
level interface to PETSc SNES.
"""
super().__init__(comm)
warnings.warn(
(
"dolfinx.nls.petsc.NewtonSolver is deprecated. "
+ "Use dolfinx.fem.petsc.NonlinearProblem, "
+ "a high level interface to PETSc SNES."
),
DeprecationWarning,
)
# Create matrix and vector to be used for assembly
# of the non-linear problem
self._A = create_matrix(problem.a)
self.setJ(problem.J, self._A)
self._b = create_vector(extract_function_spaces(problem.L)) # type: ignore
self.setF(problem.F, self._b)
self.set_form(problem.form)
def __del__(self):
for obj in filter(lambda obj: obj is not None, (self._A, self._b)):
obj.destroy()
def solve(self, u: fem.Function):
"""Solve non-linear problem into function u. Returns the number
of iterations and if the solver converged."""
n, converged = super().solve(u.x.petsc_vec)
u.x.scatter_forward()
return n, converged
@property
def A(self) -> PETSc.Mat: # type: ignore
"""Jacobian matrix"""
return self._A
@property
def b(self) -> PETSc.Vec: # type: ignore
"""Residual vector"""
return self._b
def setP(self, P: types.FunctionType, Pmat: PETSc.Mat): # type: ignore
"""
Set the function for computing the preconditioner matrix
Args:
P: Function to compute the preconditioner matrix
Pmat: Matrix to assemble the preconditioner into
"""
super().setP(P, Pmat)
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