What is the actual meanings of the abbrevations "ny" (direction), "nyP", and "nyPP" in the code?

[biergaizi]

Although I've worked with the openEMS codebase for a year and I know basically what every part of it, but I never actually understood some of the naming convention used. In the code, the variable "ny" can be x, y, z, so it stands for "direction", but why is it represented by "ny"? Similarly, in the Mur's ABC code, another two related variables are "nyP" and "nyPP". These variables have something to do with polarization, but what does nyP and nyPP actually stand for?

Once I got an answer, I hope I can either rework with naming or at least document the convention used in the comments...

[biergaizi]

From the comments

m_volt_nyP; //n+1 direction
m_volt_nyPP; //n+2 direction

So I think nyP and nyPP stands for ny_plus and ny_plusplus, that makes sense, but what about the y in ny?

[thliebig]

I think you can just ignore that. It stems I think from the thesis and it was a n_μ [n_(μ+1), n_(μ+2)] which in the code I wrote as ny. Don't ask my why, its like from 20 years ago...

[thliebig]

in a sense "n" stood for "normal"-direction and μ, μ+1, μ+2 was the index/direction

[thliebig]

I guess it could be renamed to nu, nuP, nuPP ? I tried to avoid just plain "n" (nP, nPP) as it is used often in loops etc.

[biergaizi]

After reading the code further, I think I know now. The y in ny probably means Yee, since this variable gives the direction with respect to the simulation box, on the other hand a plain n refers to the polarization direction of the vector field (not the box).

[thliebig]

I just noticed that I also used this "ny" in the python interface, so we might just explain that it stands for direction in space (usually 0,1 or 2 for x,y or z)