Memory leak when iterating Point in Python

[Steven Vandekerckhove]

from dolfin import *
import numpy as np

mesh = UnitSquareMesh(4, 4)

U = VectorFunctionSpace(mesh, "CG", 1)
u = Function(U)

p = (0.1, 0.1)

print u(p)[0] # Works
print u[0](p) # Works

p = Point(np.array((0.1, 0.1)))

print u(p)[0] # Works
print u[0](p) # Leaks

[Jan Blechta]

Two notes to u[0](p). It gives the assertion error:

*** Error:   Unable to complete call to function operator[]().
*** Reason:  Assertion i < 3 failed.
*** Where:   This error was encountered inside ../../../../../dolfin/geometry/Point.h (line 100).

The mechanism used to evaluate this is ufl_evaluate, which is very inefficient. First method u(p)[0] is strongly preferred.

[Steven Vandekerckhove]

Strange, I don't get this error in my docker container, just a memory leak... Good to know u(p)[0] is preferred.

Thanks for your comment!

[Jan Blechta]

The reason is that Point does not follow correctly Python iterable protocol.

from dolfin import *
def foo(): pass
foo(*Point())

*Point() starts unpacking the point until iteration ends. But it either never ends or fails on assertion.

[Jan Blechta]

Fixed by e12926191335f540b8014d1a9f79fbb2547b1aa4.