Residual() function not defined error (Conda fenics version 2018.1.0)

1

Hi, I’m reading some other ppl’s code and there was a function residual(A, x, b) which computes the residual value. But I got the error of residual not defined. Is there any alternative for that?

Some update, I thought the residual function was depreciated, but seems like it is not as it still works in 2019 version. So it should be my conda installation problem or version problem?

2

The following code snippet works fine for me, using FEniCS 2019.1.0:

from dolfin import *

mesh = UnitIntervalMesh(1)
V = FunctionSpace(mesh,"CG",1)
A = assemble(TrialFunction(V)*TestFunction(V)*dx)
b = assemble(TestFunction(V)*dx)
x = Function(V).vector()

print(residual(A,x,b))
print(norm(A*x-b))
3

Hi, Kamensky,

Thanks for your reply. But the same script will output an error “residual not defined.”
I’m using the conda version of FEnics. Checked the version is 2018.1.0. But I think I’ve got the latest conda package.

4

Latest conda version should be 2019.1.0

5

Hi, Dokken,

I am not sure how can I get the latest version with conda. I just followed the installation guidance and installed with
conda install -c conda-forge fenics

but after installation, I get fenics-version 2018.1.0

6

I installed docker-version 2019.1.0. Problem resolved.