consider switch to expm1

[tcaduser]

For your Bernoulli function

Genius-TCAD-Open/include/math/mathfunc.h

Line 78 in c76ade9

inline double bern ( double x )

The C++ math libraries, have an expm1 function that is easier to use when calculating exp(x)-1.

Please see:
https://en.cppreference.com/w/cpp/numeric/math/expm1

So that the Bernoulli function can be something like this:

y = expm1(x);
if (y != x)
{
    bern = x / expm(x);
}
else
{
    bern = 1.0/(1.0 + 0.5*x);
}