Hi!
I just started using FEniCS and tried to extend the example for solving
the Poisson eq. to 3D (FEniCS book page 5). When I try to evaluate the
calculated function at a specific point WITHIN the domain, I get the
following error.
***-------------------------------------------------------------------------
*** Error: Unable to evaluate function at point.
*** Reason: The point is not inside the domain. Consider setting
"allow_extrapolation" to allow extrapolation.
*** Where: This error was encountered inside Function.cpp.
*** Process: 0
***
*** DOLFIN version: 1.2.0+
*** Git changeset: 3fccc245c4f7d4f35503d0112ec2966b4946a311
*** -------------------------------------------------------------------------
I have tried various versions of calculating the function value at this
point, but didn't succeed. Other points (like (0.5, 0.5, 0.5)) work. What
am I doing wrong? I hope it's not some trivial mistake.
Thank you very much!
--
from dolfin import *
import numpy
# Mesh
mesh = UnitCubeMesh(14,14,14)
V = FunctionSpace(mesh, "Lagrange", 1)
# BC
u0 = Expression("1 + x[0]*x[0] + 2*x[1]*x[1] + x[2]*x[2]")
bc = DirichletBC(V,u0,DomainBoundary())
# Define variational problem
u, v = TrialFunction(V), TestFunction(V)
f = Constant(-6.0)
a = inner(nabla_grad(u), nabla_grad(v))*dx
L = f*v*dx
# Compute solution
u = Function(V)
set_log_level(PROGRESS)
solve(a==L,u,bc)
x = numpy.array([0.75, 0.25, 0.125])
print u(x)
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