Do not allow re-intialisation of GenericTensor/Vector/Matrix

[Prof Garth Wells]

See mailing list thread http://fenicsproject.org/pipermail/fenics/2014-January/000990.html.

[Prof Garth Wells]

Fixed in 832c1b1.

It's not anticipated that this will break any user code, but some tweaking may be required. It will issue warnings for usage that will become an error in a future version.

[Jan Blechta]

@garth-wells This

from dolfin import *

mesh = UnitSquareMesh(3, 3)

V = VectorFunctionSpace(mesh, 'CG', 1)
P = FunctionSpace(mesh, 'CG', 1)

W = MixedFunctionSpace([V, P])

v = Function(V)
w = Function(W)
w0, w1 = w.split()

v.assign(w0)

was working in 1.3.0 and now raises

*** Error:   Unable to initialize vector of degrees of freedom for function.
*** Reason:  Cannot re-initialize a non-empty vector. Consider creating a new function.
*** Where:   This error was encountered inside Function.cpp.

It can be worked-around by FunctionAssigner but shouldn't it be resolved to keep old codes working? (I have a suspicion that this is trivial.)

[Jan Blechta]

Oh, by reading again, I now probably see that this is intended behaviour.

[Jan Blechta]

Issue #291 was marked as a duplicate of this issue.

[Prof Garth Wells]

Removing milestone: 1.4 (automated comment)

[Alexandre Dufour]

Hi, I'm currently migrating some 1.2 code to 1.4 and just ran into the same issue (cannot re-initialize...). How can I use the FunctionAssigner to fix this (any 2-line example code)? I'm not well aware of the inner guts of Dolfin, hence my ignorance. Cheers

[Jan Blechta]

@adufour, please ask on http://fenicsproject.org/qa to in order to get helped.