Source term doesn't seem to do anything

[DIsrael-LANL]

I've got a more complex set of coupled 1-d PDEs, but for now, I've narrowed the error down to this simple example. Why doesn't the following work?

from fipy import Grid1D, CellVariable, TransientTerm, Viewer, ImplicitSourceTerm
from numpy import cos

m = Grid1D(nx=100, Lx=1.)
u = CellVariable(mesh=m, name="u", value=1)
eq = TransientTerm(var=u) == ImplicitSourceTerm(var=u)
vi = Viewer(u)
for t in range(10):
    eq.solve(dt=1.e-2)
    vi.plot()

I expect to see exponential growth (this is really a trivially ODE at each point), but instead the solution stays u=1 for all times.
If I write the source term explicitly, it also does not work.

If I use a source term that is spatially varying, then it works. (For example, if I set u.setValue=m.x.)

[wd15]

It seems like the default coefficient for the ImplicitSourceTerm is 0.0. I always thought the default value to be 1.0. Anyway, the following seems to work,

from fipy import Grid1D, CellVariable, TransientTerm, Viewer, ImplicitSourceTerm
from numpy import cos

m = Grid1D(nx=100, Lx=1.)
u = CellVariable(mesh=m, name="u", value=1.0)
eq = TransientTerm(var=u) == ImplicitSourceTerm(coeff=1.0, var=u)
vi = Viewer(u)
for t in range(10):
    eq.solve(dt=1.e-2)
    vi.plot()

Also, remember to set value=1.0 in the CellVariable to make it a float.

[guyer]

Yep, this issue was identified several years ago (#512), but evidently never fixed.