r_t               121 src/secOrd_op_rhs_impl.cpp   const double r_t = r_end * r_start / (r_end * e_kt + r_start * (1 - e_kt) );
r_t               123 src/secOrd_op_rhs_impl.cpp   cache[1] = k * ( 1 - r_t / r_end);