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"""Unit tests for the LUSolver interface"""
# Copyright (C) 2014 Garth N. Wells
#
# This file is part of DOLFIN.
#
# DOLFIN is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# DOLFIN is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with DOLFIN. If not, see <http://www.gnu.org/licenses/>.
from dolfin import *
import pytest
from dolfin_utils.test import skip_if_not_PETSc, skip_in_parallel
backends = ["PETSc", pytest.param(("Eigen"), marks=skip_in_parallel)]
@pytest.mark.parametrize('backend', backends)
def test_lu_solver(backend):
# Check whether backend is available
if not has_linear_algebra_backend(backend):
pytest.skip('Need %s as backend to run this test' % backend)
# Set linear algebra backend
prev_backend = parameters["linear_algebra_backend"]
parameters["linear_algebra_backend"] = backend
mesh = UnitSquareMesh(12, 12)
V = FunctionSpace(mesh, "Lagrange", 1)
u, v = TrialFunction(V), TestFunction(V)
A = assemble(Constant(1.0)*u*v*dx)
b = assemble(Constant(1.0)*v*dx)
norm = 13.0
solver = LUSolver()
x = Vector()
solver.solve(A, x, b)
assert round(x.norm("l2") - norm, 10) == 0
solver = LUSolver(A)
x = Vector()
solver.solve(x, b)
assert round(x.norm("l2") - norm, 10) == 0
solver = LUSolver()
x = Vector()
solver.set_operator(A)
solver.solve(x, b)
assert round(x.norm("l2") - norm, 10) == 0
solver = LUSolver()
x = Vector()
solver.solve(A, x, b)
assert round(x.norm("l2") - norm, 10) == 0
# Reset backend
parameters["linear_algebra_backend"] = prev_backend
@pytest.mark.parametrize('backend', backends)
def test_lu_solver_reuse(backend):
"""Test that LU re-factorisation is only performed after
set_operator(A) is called"""
# Test requires PETSc version 3.5 or later. Use petsc4py to check
# version number.
try:
from petsc4py import PETSc
except ImportError:
pytest.skip("petsc4py required to check PETSc version")
else:
if not PETSc.Sys.getVersion() >= (3, 5, 0):
pytest.skip("PETSc version must be 3.5 of higher")
# Check whether backend is available
if not has_linear_algebra_backend(backend):
pytest.skip('Need %s as backend to run this test' % backend)
# Set linear algebra backend
prev_backend = parameters["linear_algebra_backend"]
parameters["linear_algebra_backend"] = backend
mesh = UnitSquareMesh(12, 12)
V = FunctionSpace(mesh, "Lagrange", 1)
u, v = TrialFunction(V), TestFunction(V)
b = assemble(Constant(1.0)*v*dx)
A = assemble(Constant(1.0)*u*v*dx)
norm = 13.0
solver = LUSolver(A)
x = Vector()
solver.solve(x, b)
assert round(x.norm("l2") - norm, 10) == 0
assemble(Constant(0.5)*u*v*dx, tensor=A)
x = Vector()
solver.solve(x, b)
if backend != 'Eigen':
# The eigen backend only recomputes the factorization once set_operator is called
assert round(x.norm("l2") - 2.0*norm, 10) == 0
solver.set_operator(A)
solver.solve(x, b)
assert round(x.norm("l2") - 2.0*norm, 10) == 0
# Reset backend
parameters["linear_algebra_backend"] = prev_backend
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