Source code for dolfinx.nls.petsc

# Copyright (C) 2021 Jørgen S. Dokken
# This file is part of DOLFINx (
# SPDX-License-Identifier:    LGPL-3.0-or-later
"""Methods for solving nonlinear equations using PETSc solvers."""

from __future__ import annotations

import typing

if typing.TYPE_CHECKING:
    from dolfinx.fem.problem import NonlinearProblem
    from mpi4py import MPI
    from petsc4py import PETSc

import types

from dolfinx import cpp as _cpp
from dolfinx import fem

__all__ = ["NewtonSolver"]

[docs]class NewtonSolver(_cpp.nls.petsc.NewtonSolver): def __init__(self, comm: MPI.Intracomm, problem: NonlinearProblem): """A Newton solver for non-linear problems.""" super().__init__(comm) # Create matrix and vector to be used for assembly # of the non-linear problem self._A = fem.petsc.create_matrix(problem.a) self.setJ(problem.J, self._A) self._b = fem.petsc.create_vector(problem.L) self.setF(problem.F, self._b) self.set_form(problem.form) def __del__(self): self._A.destroy() self._b.destroy()
[docs] 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.vector) u.x.scatter_forward() return n, converged
@property def A(self) -> PETSc.Mat: """Jacobian matrix""" return self._A @property def b(self) -> PETSc.Vec: """Residual vector""" return self._b
[docs] def setP(self, P: types.FunctionType, Pmat: PETSc.Mat): """ 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)