imposing boundary conditions for Hermite element MixedFunctionSpace
Dear firedrake users, I try to solve a fourth-order 1d nonlinear problem using the Hermite element in firedrake. The functional space for the weak solution is: $$\mathcal{H}\times \mathcal{H}/times H^{2}_{0} $$ where, $$ \mathcal{H} = \left\lbrace f\in H^2([0,\ell]), \; f(0)=0, \; f'(0)=0 \right\rbrace. $$ I can't impose the boundary conditions correctly. When I compile the code, I get the following error: FiniteElement('Hermite', interval, 3), name=None, index=1, component=None), IndexedProxyFunctionSpace(<firedrake.mesh.MeshTopology object at 0x125a2ce80>, FiniteElement('Hermite', interval, 3), name=None, index=2, component=None), name='None_None_None'), Mesh(VectorElement(FiniteElement('Lagrange', interval, 1), dim=1), 0)), 9) defined on incompatible FunctionSpace! Note the same problem was implemented using FEniCS with C0-interior penalty method, in the reference (sec. 3 eq 3.12-3.13): Enhanced models for the nonlinear bending of planar rods: localization phenomena and multistability by: Matteo Brunetti , Antonino Favata and Stefano Vidoli. I attached the codes to this email. Thanks in advance Smail MERABET
Dear Smail, I haven't had the chance to look at your codes, but it's possible to make a subclass of DirichletBC that imposes boundary conditions on Hermite function spaces on an interval. For example, to fix the derivative at the left end-point of an interval, in the past I did import firedrake.utils as utils class FixHermiteDerivativeValue(DirichletBC): @utils.cached_property def nodes(self): if V.mesh().mpi_comm().size > 1: raise NotImplementedError return [1] # the derivative component of the first vertex at x = 0 If you wanted to set the function value, the method should return [0], etc. Hope this helps! Patrick On 11/04/2025 09:11, Smail Merabet wrote:
Dear firedrake users,
I try to solve a fourth-order 1d nonlinear problem using the Hermite element in firedrake. The functional space for the weak solution is: $$\mathcal{H}\times \mathcal{H}/times H^{2}_{0} $$ where, $$ \mathcal{H} = \left\lbrace f\in H^2([0,\ell]), \; f(0)=0, \; f'(0)=0 \right\rbrace. $$ I can't impose the boundary conditions correctly. When I compile the code, I get the following error: FiniteElement('Hermite', interval, 3), name=None, index=1, component=None), IndexedProxyFunctionSpace(<firedrake.mesh.MeshTopology object at 0x125a2ce80>, FiniteElement('Hermite', interval, 3), name=None, index=2, component=None), name='None_None_None'), Mesh(VectorElement(FiniteElement('Lagrange', interval, 1), dim=1), 0)), 9) defined on incompatible FunctionSpace!
Note the same problem was implemented using FEniCS with C0-interior penalty method, in the reference (sec. 3 eq 3.12-3.13):
Enhanced models for the nonlinear bending of planar rods: localization phenomena and multistability by: Matteo Brunetti , Antonino Favata and Stefano Vidoli.
I attached the codes to this email.
Thanks in advance Smail MERABET
_______________________________________________ firedrake mailing list firedrake@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/firedrake
Dear firedrake users, I try to solve a variational inequality using snes-firedrake. I have two unknown functions say (theta,w) so the functionspace is Vh = MixedFunctionSpace([Th,Wh]) where Th = FunctionSpace(mesh, "Lagrange", 1) Wh = FunctionSpace(mesh, "Lagrange", 2) the inequality constraint concerns only $w$ I set : obstacle = Function(Vh.sub(1)).interpolate((Constant(-0.03))) upper = Function(Vh.sub(1)).interpolate(Constant(1e10)) *solver.solve(bounds=(obstacle, upper)) * but this line causes the following error: File "/Users/maths/Desktop/Firedrake/VI/Timoshenko-obs.py", line 64, in <module> solver.solve(bounds=(obstacle, upper)) File "petsc4py/PETSc/Log.pyx", line 188, in petsc4py.PETSc.Log.EventDecorator.decorator.wrapped_func File "petsc4py/PETSc/Log.pyx", line 189, in petsc4py.PETSc.Log.EventDecorator.decorator.wrapped_func File "/Users/maths/firedrake/src/firedrake/firedrake/adjoint_utils/variational_solver.py", line 89, in wrapper out = solve(self, **kwargs) File "/Users/maths/firedrake/src/firedrake/firedrake/variational_solver.py", line 312, in solve self.snes.setVariableBounds(lb, ub) File "petsc4py/PETSc/SNES.pyx", line 1978, in petsc4py.PETSc.SNES.setVariableBounds petsc4py.PETSc.Error: error code 75 [0] SNESVISetVariableBounds() at /Users/maths/firedrake/src/petsc/src/snes/impls/vi/vi.c:424 [0] SNESVISetVariableBounds_VI() at /Users/maths/firedrake/src/petsc/src/snes/impls/vi/vi.c:443 [0] Arguments are incompatible [0] Incompatible vector lengths lower bound = 201 solution vector = 302 Hope that one can help me ... Best regards. Smail. On Fri, Apr 11, 2025 at 9:11 AM Smail Merabet <merabetsmail@gmail.com> wrote:
Dear firedrake users,
I try to solve a fourth-order 1d nonlinear problem using the Hermite element in firedrake. The functional space for the weak solution is: $$\mathcal{H}\times \mathcal{H}/times H^{2}_{0} $$ where, $$ \mathcal{H} = \left\lbrace f\in H^2([0,\ell]), \; f(0)=0, \; f'(0)=0 \right\rbrace. $$ I can't impose the boundary conditions correctly. When I compile the code, I get the following error: FiniteElement('Hermite', interval, 3), name=None, index=1, component=None), IndexedProxyFunctionSpace(<firedrake.mesh.MeshTopology object at 0x125a2ce80>, FiniteElement('Hermite', interval, 3), name=None, index=2, component=None), name='None_None_None'), Mesh(VectorElement(FiniteElement('Lagrange', interval, 1), dim=1), 0)), 9) defined on incompatible FunctionSpace!
Note the same problem was implemented using FEniCS with C0-interior penalty method, in the reference (sec. 3 eq 3.12-3.13):
Enhanced models for the nonlinear bending of planar rods: localization phenomena and multistability by: Matteo Brunetti , Antonino Favata and Stefano Vidoli.
I attached the codes to this email.
Thanks in advance Smail MERABET
On Thu, Jul 17, 2025 at 7:52 AM Smail Merabet <merabetsmail@gmail.com> wrote:
Dear firedrake users, I try to solve a variational inequality using snes-firedrake. I have two unknown functions say (theta,w) so the functionspace is Vh = MixedFunctionSpace([Th,Wh]) where Th = FunctionSpace(mesh, "Lagrange", 1) Wh = FunctionSpace(mesh, "Lagrange", 2)
the inequality constraint concerns only $w$
I set : obstacle = Function(Vh.sub(1)).interpolate((Constant(-0.03))) upper = Function(Vh.sub(1)).interpolate(Constant(1e10))
The SNES is operating on the full space, but you have interpolated constraints on the subspace. You have to inject those to full space vectors before setting the bounds. Thanks, Matt
*solver.solve(bounds=(obstacle, upper)) *
but this line causes the following error:
File "/Users/maths/Desktop/Firedrake/VI/Timoshenko-obs.py", line 64, in <module> solver.solve(bounds=(obstacle, upper)) File "petsc4py/PETSc/Log.pyx", line 188, in petsc4py.PETSc.Log.EventDecorator.decorator.wrapped_func File "petsc4py/PETSc/Log.pyx", line 189, in petsc4py.PETSc.Log.EventDecorator.decorator.wrapped_func File "/Users/maths/firedrake/src/firedrake/firedrake/adjoint_utils/variational_solver.py", line 89, in wrapper out = solve(self, **kwargs) File "/Users/maths/firedrake/src/firedrake/firedrake/variational_solver.py", line 312, in solve self.snes.setVariableBounds(lb, ub) File "petsc4py/PETSc/SNES.pyx", line 1978, in petsc4py.PETSc.SNES.setVariableBounds petsc4py.PETSc.Error: error code 75 [0] SNESVISetVariableBounds() at /Users/maths/firedrake/src/petsc/src/snes/impls/vi/vi.c:424 [0] SNESVISetVariableBounds_VI() at /Users/maths/firedrake/src/petsc/src/snes/impls/vi/vi.c:443 [0] Arguments are incompatible [0] Incompatible vector lengths lower bound = 201 solution vector = 302
Hope that one can help me ...
Best regards. Smail.
On Fri, Apr 11, 2025 at 9:11 AM Smail Merabet <merabetsmail@gmail.com> wrote:
Dear firedrake users,
I try to solve a fourth-order 1d nonlinear problem using the Hermite element in firedrake. The functional space for the weak solution is: $$\mathcal{H}\times \mathcal{H}/times H^{2}_{0} $$ where, $$ \mathcal{H} = \left\lbrace f\in H^2([0,\ell]), \; f(0)=0, \; f'(0)=0 \right\rbrace. $$ I can't impose the boundary conditions correctly. When I compile the code, I get the following error: FiniteElement('Hermite', interval, 3), name=None, index=1, component=None), IndexedProxyFunctionSpace(<firedrake.mesh.MeshTopology object at 0x125a2ce80>, FiniteElement('Hermite', interval, 3), name=None, index=2, component=None), name='None_None_None'), Mesh(VectorElement(FiniteElement('Lagrange', interval, 1), dim=1), 0)), 9) defined on incompatible FunctionSpace!
Note the same problem was implemented using FEniCS with C0-interior penalty method, in the reference (sec. 3 eq 3.12-3.13):
Enhanced models for the nonlinear bending of planar rods: localization phenomena and multistability by: Matteo Brunetti , Antonino Favata and Stefano Vidoli.
I attached the codes to this email.
Thanks in advance Smail MERABET
_______________________________________________ firedrake mailing list firedrake@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/firedrake
-- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
participants (3)
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Matthew Knepley
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Patrick Farrell
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Smail Merabet