pub fn build_cn_tridiag(
chi: &Array1<f64>,
rho: &Array1<f64>,
dt: f64,
) -> (Vec<f64>, Vec<f64>, Vec<f64>, Vec<f64>)Expand description
Build Crank-Nicolson tridiagonal coefficients for 1D diffusion.
Returns (a, b, c, d) where a/b/c are sub/main/super diagonals for
fusion_math::tridiag::thomas_solve and d is a zero-initialized RHS
template that callers may fill with source terms.