for(int j=0; j < N; ++j) fill_gaussian(d.elem(i), r1.elem(i), r2.elem(i));
fill_gaussian(d.elem(i), r1.elem(i), r2.elem(i));
fill_gaussian(PVector<T,N,C>& d, PVector<T,N,C>& r1, PVector<T,N,C>& r2){  for(int i=0; i < N; ++i)    for(int j=0; j < N; ++j)      fill_gaussian(d.elem(i), r1.elem(i), r2.elem(i));}