Bessel functions as CoefficientFunctions

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1

Hi,

I want to use the bessel function from a python library (for example scipy.special) as a CoefficientFunctions.

my code:
from ngsolve import *
from scipy.special import jn #import bessel J function
uexact = jn(1,x)

I get the following error:
uexact = jn(1,x)
TypeError: ufunc ‘jv’ not supported for the input types, and the inputs could not be safely coerced to any supported types according to the casting rule ‘‘safe’’

Is there a way to use these functions from a python library as CoefficentFunction?

Thank you,

Renzo

2

Hi, no you cannot use scipy functions as coefficients, but we have the ngs-special-functions addon that provides these functions:

Best
Christopher

3

Hi Christopher,
Thank you for your answer!
I followed the instruction to install the package on Linux and I tried to run the demo bessel.py but I get an import error:

ImportError: /home/c/rzanol/.local/lib/python3.8/site-packages/ngsolve/special_functions.so: undefined symbol: _ZNK5ngfem19CoefficientFunction14GetDescriptionB5cxx11Ev

Do you have any idea what could be the problem?

4

Hi, i tried to install ngs-special-functions as decribed on GitHub repository.
However i do not have “make” command, probably due to missing VC toolchain on my Win11 pc.
What toolchain would you recomend installing for best compatibility on Win11?
Sorry for the beginner question.

5

follow the build/install instruction from

could you run cmake ?

6

Thank you for Your quick replay joachim.

  • I followed the GitHub instruction.
  • the cmake … worked wihout error message
  • it created some *.vcxproj, *.filters and ngsolve_special_functions.sln
  • but on my system i do not have make

i think i have to do some compatible tool chain instalation.
i have

  • win11
  • conda
  • installed ngsolve via: pip install --pre --upgrade ngsolve
  • where cl returns: C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.39.33519\bin\Hostx64\x64\cl.