Function multi_port_nr_solve 

pub fn multi_port_nr_solve(
    n_nl: usize,
    s_nl: &[f64],
    known_a: &[f64],
    port_resistances: &[f64],
    devices: &[&dyn NlDeviceIv],
    v_guess: &mut [f64],
    max_iter: usize,
    tolerance: f64,
) -> Vec<f64>

Multi-port Newton-Raphson solver for coupled nonlinear WDF elements.

For N nonlinear ports on an R-type adaptor, the system of equations is:

F_i(v) = known_a_i + Σ_j S_nl[i][j]·(-2·R_j·i_j(v_j)) - 2·v_i = 0

where known_a[i] includes contributions from all passive/adapted ports, and S_nl is the NL-to-NL sub-block of the scattering matrix.

The Jacobian is:

J[i][j] = S_nl[i][j]·(-2·R_j)·(di_j/dv_j)           for j ≠ i
J[i][i] = S_nl[i][i]·(-2·R_i)·(di_i/dv_i) - 2        for j = i

Parameters

• n_nl: Number of coupled nonlinear ports
• s_nl: NL-to-NL scattering sub-block (n_nl × n_nl, row-major)
• known_a: Pre-computed incident wave contributions from passive ports (n_nl)
• port_resistances: Port resistance for each NL port (n_nl)
• devices: NL device I-V evaluators (n_nl)
• v_guess: Warm-start voltages, mutated to final solution (n_nl)
• max_iter: Maximum Newton-Raphson iterations
• tolerance: Convergence threshold for |dv|

Returns

Reflected wave b[i] for each NL port.