problems with the docs

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1

I am brand new to ngsolve but installed it today and and keen to learn to use it. There are a couple of problems that I found in the docs and I am not sure if it is well known or not.

First, in installing ngsolve on jupyter on my ubuntu system, I needed to install jupyter-notebook as well, and the install command did not work but needed to use enable, as copied below.

sudo apt install jupyter-notebook
jupyter nbextension enable ngsolve --user --py

Second, I found about 6 or so examples in the notebooks that did not run, the first of which was the notebook on Maxwells equations. I can provide a longer list if need be.

I presume these are known but wanted to try and contribute in case they aren’t.

2

Hi Poulin,

welcome to NGSolve. Yes, please tell us what is not working.

You may also watch the tutorials on youtube to see how they should work, e.g. the Maxwell tutorial:

Joachim

3

Hello Joachim,

Thanks for sharing this video wtih me.

I understand the setup of the code but the problem I had was with an error.

In particular, I am copying the error message below. I will copy other errors that I get in the other codes in separate lines.

AttributeError Traceback (most recent call last)
in
5 from math import pi
6 mu0 = 4pi1e-7
----> 7 mur = mesh.MaterialCF({“magnet” : 1000}, default=1)
8
9 a = BilinearForm(fes)

AttributeError: ‘ngsolve.comp.Mesh’ object has no attribute ‘MaterialCF’

4

2.6 Stokes Equation

TypeError Traceback (most recent call last)
in
1 V = H1(mesh, order=2, dirichlet=“wall|inlet|cyl”)
2 Q = H1(mesh, order=1)
----> 3 X = VVQ

TypeError: unsupported operand type(s) for *: ‘ngsolve.comp.H1’ and ‘ngsolve.comp.H1’

5

2.11 Matrix free operator application¶

NameError Traceback (most recent call last)
in
2 felS = Sigma.GetFE(el)
3 felV = V.GetFE(el)
----> 4 fel = MixedFE(felS, felV)
5 trafo = mesh.GetTrafo(el)
6

NameError: name ‘MixedFE’ is not defined

6

3.3 Discontinuous Galerkin Discretizations for linear transport

TypeError Traceback (most recent call last)
in
1 # this does not work:
2 c2 = BilinearForm(VT)
----> 3 res.data = c2.mat * gfu.vec

TypeError: matrix not ready - assemble bilinearform first

7

looks like you have an elder version of NGSolve, these are all quite new features

you can print the active version via

print (ngsolve.__version__)

current version is 2008

in the online documentation you can choose the ngsolve-version at the bottom of the menu on the left.

Joachim

8

Thank you for the help.

When I am in a notebook and I type the line that you suggested, after importing ngsolve, I get an error

NameError Traceback (most recent call last)
in
1 from ngsolve import *
----> 2 print (ngsolve.version)

NameError: name ‘ngsolve’ is not defined

However, when I am in the terminal and typ in netgen I see I’m using a very old version,

$ netgen
NETGEN-6.2.2007
Developed by Joachim Schoeberl at
2010-xxxx Vienna University of Technology
2006-2010 RWTH Aachen University
1996-2006 Johannes Kepler University Linz
Including OpenCascade geometry kernel
optfile ./ng.opt does not exist - using default values
togl-version : 2
OCC module loaded
loading ngsolve library
NGSolve-6.2.2007
Using Lapack
Including sparse direct solver UMFPACK
Running parallel using 36 thread(s)
importing NGSolve-6.2.2007

This is what installed in ubuntu usin apt-get.

To get a newer version do you recommend I build them from source?

9

To get the latest version I decided to build from source. Everything seemed to go well until it was scannin gdependencies of target ngstd, and that’s where it failed because of an error. Should I post this until a different problem?

Scanning dependencies of target ngstd
[ 1%] Building CXX object ngstd/CMakeFiles/ngstd.dir/blockalloc.cpp.o
In file included from /home/fpoulin/software/ngsolve-src/ngstd/ngstd.hpp:14,
from /home/fpoulin/software/ngsolve-src/ngstd/blockalloc.cpp:12:
/home/fpoulin/software/ngsolve-src/include/ngs_stdcpp_include.hpp:43:2: error: #error “GCC 9.1/9.2 generates wrong code on AVX512 platforms (see 93009 – [9 Regression] AVX512 FMA - wrong code generation since r265288 ). Either build for a different architecture (cmake -DUSE_NATIVE=OFF), or use a different compiler (like GCC 8.3 or Clang)”
43 | #error “GCC 9.1/9.2 generates wrong code on AVX512 platforms (see 93009 – [9 Regression] AVX512 FMA - wrong code generation since r265288 ). Either build for a different architecture (cmake -DUSE_NATIVE=OFF), or use a different compiler (like GCC 8.3 or Clang)”
| ^~~~~
make[5]: *** [ngstd/CMakeFiles/ngstd.dir/build.make:63: ngstd/CMakeFiles/ngstd.dir/blockalloc.cpp.o] Error 1
make[4]: *** [CMakeFiles/Makefile2:173: ngstd/CMakeFiles/ngstd.dir/all] Error 2
make[3]: *** [Makefile:141: all] Error 2
make[2]: *** [CMakeFiles/ngsolve.dir/build.make:116: dependencies/Stamp/ngsolve/ngsolve-build] Error 2
make[1]: *** [CMakeFiles/Makefile2:222: CMakeFiles/ngsolve.dir/all] Error 2
make: *** [Makefile:152: all] Error 2

10

Hello,

Concerning the apt-get version: Which Ubuntu version do you have? Note that 19.10 is already end-of-life and not receiving updates anymore.

Concerning the compiler error: Your compiler version is buggy, that’s why we had to explicitly block it. One way to work around it, is configuring cmake with
-DUSE_NATIVE_ARCH=OFF
which results in sub-optimal performance of the generated code (no AVX instructions used).

I think both of your issues could be solved by an Ubuntu upgrade.

Best,
Matthias

11

Thank you Matthias.

I will certainly get my ubuntu machine upgraded.

For the moment I have used the configuration that you suggested and have been able to install version 6.2.2008 with success. I admit that the instructions I found in the docs did not quite work in setting up the PYTHONPATH but I figured out what it should be so I’m happy about that.

I can also verify that the Maxwells example does work, and I suspect the others will work as well.

Thanks everyone for the help!