def F(self, snes, x, F):
"""Assemble residual vector."""
x.ghostUpdate(addv=PETSc.InsertMode.INSERT, mode=PETSc.ScatterMode.FORWARD)
x.copy(self.u.vector())
self.u.vector().ghostUpdate(addv=PETSc.InsertMode.INSERT, mode=PETSc.ScatterMode.FORWARD)
with F.localForm() as f_local:
f_local.set(0.0)
fem.assemble_vector(F, self.L)
fem.apply_lifting(F, [self.a], [[self.bc]], [x], -1.0)
F.ghostUpdate(addv=PETSc.InsertMode.ADD, mode=PETSc.ScatterMode.REVERSE)
fem.set_bc(F, [self.bc], x, -1.0)
def F(self, x):
"""Assemble residual vector."""
if self._F is None:
self._F = fem.assemble_vector(self.L)
else:
with self._F.localForm() as f_local:
f_local.set(0.0)
self._F = fem.assemble_vector(self._F, self.L)
dolfin.fem.apply_lifting(self._F, [self.a], [[self.bc]], [x], -1.0)
self._F.ghostUpdate(addv=PETSc.InsertMode.ADD, mode=PETSc.ScatterMode.REVERSE)
dolfin.fem.set_bc(self._F, [self.bc], x, -1.0)
return self._F
def test_ghost_mesh_assembly(mode, dx, ds):
mesh = UnitSquareMesh(MPI.comm_world, 12, 12, ghost_mode=mode)
V = FunctionSpace(mesh, ("Lagrange", 1))
u, v = TrialFunction(V), TestFunction(V)
dx = dx(mesh)
ds = ds(mesh)
f = Function(V)
with f.vector.localForm() as f_local:
f_local.set(10.0)
a = inner(f * u, v) * dx + inner(u, v) * ds
L = inner(f, v) * dx + inner(2.0, v) * ds
# Initial assembly
A = fem.assemble_matrix(a)
A.assemble()
assert isinstance(A, PETSc.Mat)
b = fem.assemble_vector(L)
b.ghostUpdate(addv=PETSc.InsertMode.ADD, mode=PETSc.ScatterMode.REVERSE)
assert isinstance(b, PETSc.Vec)
# Check that the norms are the same for all three modes
normA = A.norm()
assert normA == pytest.approx(0.6713621455570528, rel=1.e-6, abs=1.e-12)
normb = b.norm()
assert normb == pytest.approx(1.582294032953906, rel=1.e-6, abs=1.e-12)
def test_krylov_solver_lu():
mesh = UnitSquareMesh(MPI.comm_world, 12, 12)
V = FunctionSpace(mesh, ("Lagrange", 1))
u, v = TrialFunction(V), TestFunction(V)
a = inner(u, v) * dx
L = inner(1.0, v) * dx
A = assemble_matrix(a)
A.assemble()
b = assemble_vector(L)
b.ghostUpdate(addv=PETSc.InsertMode.ADD, mode=PETSc.ScatterMode.REVERSE)
norm = 13.0
solver = PETScKrylovSolver(mesh.mpi_comm())
solver.set_options_prefix("test_lu_")
PETScOptions.set("test_lu_ksp_type", "preonly")
PETScOptions.set("test_lu_pc_type", "lu")
solver.set_from_options()
x = A.createVecRight()
solver.set_operator(A)
solver.solve(x, b)
# *Tight* tolerance for LU solves
assert round(x.norm(PETSc.NormType.N2) - norm, 12) == 0
def amg_solve(N, method):
# Elasticity parameters
E = 1.0e9
nu = 0.3
mu = E / (2.0 * (1.0 + nu))
lmbda = E * nu / ((1.0 + nu) * (1.0 - 2.0 * nu))
# Stress computation
def sigma(v):
return 2.0 * mu * sym(grad(v)) + lmbda * tr(sym(
grad(v))) * Identity(2)
# Define problem
mesh = UnitSquareMesh(MPI.comm_world, N, N)
V = VectorFunctionSpace(mesh, 'Lagrange', 1)
bc0 = Function(V)
with bc0.vector().localForm() as bc_local:
bc_local.set(0.0)
def boundary(x, only_boundary):
return [only_boundary] * x.shape(0)
bc = DirichletBC(V.sub(0), bc0, boundary)
u = TrialFunction(V)
v = TestFunction(V)
# Forms
a, L = inner(sigma(u), grad(v)) * dx, dot(ufl.as_vector(
(1.0, 1.0)), v) * dx
# Assemble linear algebra objects
A = assemble_matrix(a, [bc])
A.assemble()
b = assemble_vector(L)
apply_lifting(b, [a], [[bc]])
b.ghostUpdate(addv=PETSc.InsertMode.ADD,
mode=PETSc.ScatterMode.REVERSE)
set_bc(b, [bc])
# Create solution function
u = Function(V)
# Create near null space basis and orthonormalize
null_space = build_nullspace(V, u.vector())
# Attached near-null space to matrix
A.set_near_nullspace(null_space)
# Test that basis is orthonormal
assert null_space.is_orthonormal()
# Create PETSC smoothed aggregation AMG preconditioner, and
# create CG solver
solver = PETScKrylovSolver("cg", method)
# Set matrix operator
solver.set_operator(A)
# Compute solution and return number of iterations
return solver.solve(u.vector(), b)
def test_krylov_solver_lu():
mesh = UnitSquareMesh(MPI.comm_world, 12, 12)
V = FunctionSpace(mesh, ("Lagrange", 1))
u, v = TrialFunction(V), TestFunction(V)
a = inner(u, v) * dx
L = inner(1.0, v) * dx
A = assemble_matrix(a)
A.assemble()
b = assemble_vector(L)
b.ghostUpdate(addv=PETSc.InsertMode.ADD, mode=PETSc.ScatterMode.REVERSE)
norm = 13.0
solver = PETSc.KSP().create(mesh.mpi_comm())
solver.setOptionsPrefix("test_lu_")
opts = PETSc.Options("test_lu_")
opts["ksp_type"] = "preonly"
opts["pc_type"] = "lu"
solver.setFromOptions()
x = A.createVecRight()
solver.setOperators(A)
solver.solve(b, x)
# *Tight* tolerance for LU solves
assert x.norm(PETSc.NormType.N2) == pytest.approx(norm, abs=1.0e-12)
def F(self, x):
"""Assemble residual vector."""
if self._F is None:
self._F = fem.assemble_vector([self.L], [[self.a]], [self.bc],
dolfin.cpp.fem.BlockType.monolithic,
x)
else:
self._F = fem.assemble(self._F, self.L, [self.a], [self.bc], x)
return self._F
def _solve_varproblem(*args, **kwargs):
"Solve variational problem a == L or F == 0"
# Extract arguments
eq, u, bcs, J, tol, M, form_compiler_parameters, petsc_options \
= _extract_args(*args, **kwargs)
# Solve linear variational problem
if isinstance(eq.lhs, ufl.Form) and isinstance(eq.rhs, ufl.Form):
a = fem.Form(eq.lhs, form_compiler_parameters=form_compiler_parameters)
L = fem.Form(eq.rhs, form_compiler_parameters=form_compiler_parameters)
b = fem.assemble_vector(L._cpp_object)
fem.apply_lifting(b, [a._cpp_object], [bcs])
b.ghostUpdate(addv=PETSc.InsertMode.ADD,
mode=PETSc.ScatterMode.REVERSE)
fem.set_bc(b, bcs)
A = fem.assemble_matrix(a._cpp_object, bcs)
A.assemble()
comm = L._cpp_object.mesh().mpi_comm()
ksp = PETSc.KSP().create(comm)
ksp.setOperators(A)
ksp.setOptionsPrefix("dolfin_solve_")
opts = PETSc.Options()
opts.prefixPush("dolfin_solve_")
for k, v in petsc_options.items():
opts[k] = v
opts.prefixPop()
ksp.setFromOptions()
ksp.solve(b, u.vector)
ksp.view()
# Solve nonlinear variational problem
else:
raise RuntimeError("Not implemented")
def _solve_varproblem(*args, **kwargs):
"Solve variational problem a == L or F == 0"
# Extract arguments
eq, u, bcs, J, tol, M, form_compiler_parameters, petsc_options \
= _extract_args(*args, **kwargs)
# Solve linear variational problem
if isinstance(eq.lhs, ufl.Form) and isinstance(eq.rhs, ufl.Form):
a = fem.Form(eq.lhs, form_compiler_parameters=form_compiler_parameters)
L = fem.Form(eq.rhs, form_compiler_parameters=form_compiler_parameters)
b = fem.assemble_vector(L._cpp_object)
fem.apply_lifting(b, [a._cpp_object], [bcs])
b.ghostUpdate(addv=PETSc.InsertMode.ADD, mode=PETSc.ScatterMode.REVERSE)
fem.set_bc(b, bcs)
A = fem.assemble_matrix(a._cpp_object, bcs)
A.assemble()
comm = L._cpp_object.mesh().mpi_comm()
solver = cpp.la.PETScKrylovSolver(comm)
solver.set_options_prefix("dolfin_solve_")
for k, v in petsc_options.items():
cpp.la.PETScOptions.set("dolfin_solve_" + k, v)
solver.set_from_options()
solver.set_operator(A)
solver.solve(u.vector, b)
# Solve nonlinear variational problem
else:
raise RuntimeError("Not implemented")
v = TestFunction(V)
a = inner(sigma(u), grad(v)) * dx
L = inner(f, v) * dx
u0 = Function(V)
with u0.vector.localForm() as bc_local:
bc_local.set(0.0)
# Set up boundary condition on inner surface
bc = DirichletBC(V, u0, boundary)
# Assemble system, applying boundary conditions and preserving symmetry)
A = assemble_matrix(a, [bc])
A.assemble()
b = assemble_vector(L)
apply_lifting(b, [a], [[bc]])
b.ghostUpdate(addv=PETSc.InsertMode.ADD, mode=PETSc.ScatterMode.REVERSE)
set_bc(b, [bc])
# Create solution function
u = Function(V)
# Create near null space basis (required for smoothed aggregation AMG).
null_space = build_nullspace(V)
# Attach near nullspace to matrix
A.setNearNullSpace(null_space)
# Set solver options
opts = PETSc.Options()
def project(v, V=None, bcs=[], mesh=None, funct=None):
"""Return projection of given expression *v* onto the finite element
space *V*.
*Arguments*
v
a :py:class:`Function <dolfin.functions.function.Function>` or
an :py:class:`Expression <dolfin.functions.expression.Expression>`
bcs
Optional argument :py:class:`list of DirichletBC
<dolfin.fem.bcs.DirichletBC>`
V
Optional argument :py:class:`FunctionSpace
<dolfin.functions.functionspace.FunctionSpace>`
mesh
Optional argument :py:class:`mesh <dolfin.cpp.Mesh>`.
funct
Target function where result is stored.
*Example of usage*
.. code-block:: python
v = Expression("sin(pi*x[0])")
V = FunctionSpace(mesh, "Lagrange", 1)
Pv = project(v, V)
This is useful for post-processing functions or expressions
which are not readily handled by visualization tools (such as
for example discontinuous functions).
"""
# Try figuring out a function space if not specified
if V is None:
# Create function space based on Expression element if trying
# to project an Expression
if isinstance(v, function.Expression):
if mesh is not None and isinstance(mesh, cpp.mesh.Mesh):
V = function.FunctionSpace(mesh, v.ufl_element())
# else:
# cpp.dolfin_error("projection.py",
# "perform projection",
# "Expected a mesh when projecting an Expression")
else:
# Otherwise try extracting function space from expression
V = _extract_function_space(v, mesh)
# Check arguments
# Ensure we have a mesh and attach to measure
if mesh is None:
mesh = V.mesh
dx = ufl.dx(mesh)
# Define variational problem for projection
w = function.TestFunction(V)
Pv = function.TrialFunction(V)
a = ufl.inner(Pv, w) * dx
L = ufl.inner(v, w) * dx
# Assemble linear system
A = fem.assemble_matrix(a, bcs)
A.assemble()
b = fem.assemble_vector(L)
fem.apply_lifting(b, [a], [bcs])
b.ghostUpdate(addv=PETSc.InsertMode.ADD, mode=PETSc.ScatterMode.REVERSE)
fem.set_bc(b, bcs)
# Solve linear system for projection
if funct is None:
funct = function.Function(V)
la.solve(A, funct.vector, b)
return funct
