Segmentation fault during interpolation

9 months ago by
Hi everyone,

I am solving a problem that requires an adaptive solver and load ramping for convergence.
Since I was always confronted with segmentation faults, I made this very simple problem that recreates the issue:
# coding: utf-8

from fenics import *
from dolfin import *


epsilon0 = 8.854187e-12 # F/m
epsilonr = 1.0e6
epsilon = epsilon0*epsilonr

def adaptive_Poisson(mesh, previous_solution, surface_charge_value) :
    Element = FiniteElement('Lagrange', mesh.ufl_cell(), 1)   
    Space = FunctionSpace(mesh, Element)

    bc = DirichletBC(Space, 0., left)
    u = TrialFunction(Space)
    w = TestFunction(Space)

    equation = -dot(grad(w), grad(u))*dx + surface_charge_value*w*ds

    sol = Function(Space)
    print('before interpolation')
    sol.interpolate(previous_solution) #assign the previous solution as starting value
    print('after interpolation')
    R = action(equation, sol)
    DR = derivative(R, sol)
    problem = NonlinearVariationalProblem(R, sol, bc, DR)

    goal = sol*dx
    solver = AdaptiveNonlinearVariationalSolver(problem, goal)
    solver_tol = 1.0e-8

    return mesh.leaf_node(), sol.leaf_node()

class LeftBoundary(SubDomain):
    def inside(self, x, on_boundary): 
         return on_boundary and near(x[0], 0, tol)

left = LeftBoundary()  

domain_length = 1.
mesh = IntervalMesh(500, 0, domain_length)
surface_charge_value = 1.0e-3
sol = Constant(0)

for ll in range(100) :
    print('solving interation: ', ll)
    mesh, sol = adaptive_Poisson(mesh, sol, surface_charge_value)
    surface_charge_value = 1.1*surface_charge_value

The segmentation fault always occurs during the sol.interpolate() command.
The weird thing is that the program crashes in a random iteration and not necessarily in the first.

Does anyone know what I am doing wrong or how I can solve this problem?
I am running Fenics 2017.1.0 in Anaconda 4.4.0. The OS is Kubuntu 17.04 and the machine has 64 GB of RAM (thus not a problem of insufficient memory).

Thank you for your answers,
Community: FEniCS Project
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