NGSpy and boost::bessel

[Sofi Esterhazy]

Hey there!!

I would be very much interested to export the bessel function from boost into NGSpy!!

I was hoping this could be done by adapting the ExportStdMathFunction to ExportSplMathFunction which accepts two arguments the order of the bessel function v and the postion x.

So something like that in <python_fem.cpp>:</python_fem.cpp>

#include <boost/math/special_functions/bessel.hpp>

template <typename FUNC> **// adapt for two arguments ??**
void ExportSplMathFunction(string name)
{
  bp::def (name.c_str(), FunctionPointer
           ([] (bp::object x) -> bp::object
            {
              FUNC func;
              if (bp::extract<SPCF>(x).check())
                {
                  auto coef = bp::extract<SPCF>(x)();
                  return bp::object(UnaryOpCF(coef, func, func, FUNC::Name()));
                }
              bp::extract<double> ed(x);
              if (ed.check()) return bp::object(func(ed(),ed()));  **// <- two arguments !?**
              // if (bp::extract<Complex> (x).check())
              //   return bp::object(func(ed(),bp::extract<Complex> (x)()));  **// <- two arguments !?**
              throw Exception ("can't compute math-function");
            }));
}

So that I can use:

struct GenericBessel_J {
  template <typename T> T operator() (T v, T x) const { return cyl_bessel_j(v,x); } // from boost
  static string Name() { return "Bessel_J"; }

for

ExportSplMathFunction<GenericBessel_J>("Bessel_J");

Thank you very much!!

CheerS

[Joachim Schoeberl]

Hi Sofi,

you can do it like the atan2, which also uses 2 arguments,

Joachim

[Joachim Schoeberl]

Hi Sofi,

you can now export unary functions (binary functions may come soon) from a separate module, without changing the NGSolve code. It is explained in our brand-new NGSolve-Blog:
https://ngsolve.sourceforge.io/index.php/blog/ngsolve/9-exporting-mathematical-functions

Joachim