Is it possible to compute the gradient of a Functional only at a specific point with dolfin-adjoint?
6 months ago by
I have a problem where I need the gradient of a (dolfin-adjoint) Functional but only at a specific point (and not over the whole domain, as I can solve this right now).
In my working example this would be something like
J = Functional(0.5*inner(u(eval_point) - u_exact(eval_point), u(eval_point) - u_exact(eval_point))*dx)
J = Functional(0.5*inner(u - u_exact, u - u_exact)*dx)
(which works fine)
from dolfin import * from dolfin_adjoint import * import numpy as np eval_point = np.array([[0.5],[0.5]]) mesh = UnitSquareMesh(16, 16) V = FunctionSpace(mesh, "CG", 1) M = FunctionSpace(mesh, "DG", 0) def G(m): u = Function(V, name="observation") v = TestFunction(V) def left_boundary(x, on_boundary): return on_boundary and near(x, 0.0) def right_boundary(x, on_boundary): return on_boundary and near(x, 1.0) def top_boundary(x, on_boundary): return on_boundary and near(x, 1.0) right = AutoSubDomain(right_boundary) top = AutoSubDomain(top_boundary) markers = FacetFunction("size_t", mesh, 0) markers.set_all(0) top.mark(markers, 1) right.mark(markers, 1) ds = Measure('ds', domain=mesh, subdomain_data=markers) F = inner(m*grad(u), grad(v))*dx - Constant(1.0)*v*ds(1) bc = DirichletBC(V, 0.0, left_boundary) solve(F == 0, u, bcs=bc) return u # exact thermal conductivity m_exact_M = interpolate(Expression("exp(-((x - 0.5)*(x - 0.5)/2.0*10.0) - ((x - 0.5)*(x - 0.5)/2.0*10.0)) + 2.0", degree=2), M) u_exact = G(m_exact_M) 'The part of major relevance__________________________________________________' m = interpolate(Constant(3.0), M, name="parameter") u = G(m) J = Functional(0.5*inner(u - u_exact, u - u_exact)*dx) m_c = Control(m) gradient = compute_gradient(J, m_c)
Is there a way to avoid integration over the whole domain and evaluate this functional at a specific point (with dolfin-adjoint)?I’ve already tried to solve this with a Dirac function, but gradient checking didn’t show the same results. Maybe there’s a way to do this with MeshFunctions?
I used conda-forge to install fenics and dolfin-adjoint
Thanks for your help!
Community: FEniCS Project
6 months ago by
J = Functional(0.5*inner(u - u_exact, u - u_exact)*dx(1))
where the cells around your point you care about are marked "1".
Please login to add an answer/comment or follow this question.