Updating Fenics Vol 1 Demos

1

Hi all, I am currently going through all the annotated examples. Like many have already stated, a lot of the code is outdated but I have managed to find answers for these issues up to this point. I am currently on the “Poisson Extended” (example 10 which is available on the Fenics site) and have managed to clear some of the code that will throw errors such as:

Removing the
Interactive()
line at the bottom of the code

Changing
nr = input('Pick a demo: ') to nr = int(input('Pick a demo: '))
this line is located very close to the bottom of the code

And have even found an updated version of the
boxfield
library

However, even with all this, when I try to run the code I get this error:
AttributeError: ‘dolfin.cpp.parameter.Parameters’ object has no attribute ‘linear_solver’

If anyone has done this example or knows how to fix this issue I’d appreciate the help, thank you.

2

Dear Erik,

Next time you post here, please provide the link to the given demo you are modifying (or post the code here.
I am guessing you are referring to: https://fenicsproject.org/pub/tutorial/sphinx1/._ftut1006.html
The issue you have in the demo can be fixed by:

    prm = LinearVariationalSolver.default_parameters()
    if linear_solver == 'Krylov':
        prm["linear_solver"] = 'gmres'
        prm["preconditioner"] = 'ilu'
        prm["krylov_solver.absolute_tolerance"] = abs_tol
        prm["krylov_solver.relative_tolerance"] = rel_tol
        prm["krylov_solver.maximum_iterations"] = max_iter
    else:
        prm["linear_solver"] = 'lu'

These has been quite a few changes since the demos were released, and many of the changes are listed in the Changelog

1 Like
3

Total newbie here: I’m working through the tutorial vol.1 demos and dealing with issues as they arise. The fix given above is incorrect; the correct one is given here:

RuntimeError: Parameter krylov_solver.absolute_tolerance not found in Parameters object

Also: the link to the Changelog is broken.

4

An updated link to the changelog can be found here: Bitbucket