[JOSS REVIEW] first example fails

[thelfer]

The following example, taken from https://ngspetsc.readthedocs.io/en/latest/PETScKSP/poisson.py.html, fails as follows:

$ python3 poisson.py 
optfile ./ng.opt does not exist - using default values
togl-version : 2
loading ngsolve library
NGSolve-6.2.2405-28-g63cfc18ca
Using Lapack
Including sparse direct solver UMFPACK
Running parallel using 32 thread(s)
Traceback (most recent call last):
  File "/home/th202608/codes/ngsPETSc/tests/Poisson/poisson.py", line 7, in <module>
    ngmesh = unit_square.GenerateMesh(maxh=0.1)
NameError: name 'unit_square' is not defined

[UZerbinati]

This example is running for me on a fresh install and on the docker image.
Could it be that something went wrong with your ngsolve install?

[thelfer]

I just followed your tutorial steps by steps. ngsolve did get installed, so I expect that there is a dependency missing.

[UZerbinati]

Did you install it with -DUSE_OCC=OFF instead of the default -DUSE_OCC=ON ?

[thelfer]

must check

[UZerbinati]

Because unit_square has lately become an OCC object in ngsolve hence, if you install without OCC support it might not be there.
You should be able to test the code even without OCC if you use from netgen.geom2d import unit_square.

[thelfer]

Indeed. I remember that I removed it because OCC was not listed as a dependency to ngsolve

[thelfer]

I think that you have two choices :)

• update the installation guide to include OCC as a mandatory dependency
• update your examples

[UZerbinati]

We have included include OCC as a mandatory dependency (we will also change the pyproject.toml in next PR).

[thelfer]

Hi @UZerbinati,

Sorry for being so slow.

I reinstalled ngsolve, but there is still an issue with your install instructions: I had to add this package to be able to build ngsolve with OpenCascade enabled:

$ pip install  netgen-occt-devel

As a suggestion, I would add this line in your tutorial after the call to Draw:

input("Press the <ENTER> key to continue...")

[UZerbinati]

Thank you for spotting this. It has been fixed in PR #65.