pub fn ntt_inv(f: &mut [i16; 256])Expand description
Inverse NTT (Algorithm 10) — full Montgomery.
Input: NTT-domain (from basemul, in /R domain), |c| <= q. Output: standard-domain, |c| <= q after final scaling.
Uses negative Montgomery zetas: -ZETAS_MONT[k].
GS butterfly: f[j] = t + f[j+l], f[j+l] = fqmul(-z, t - f[j+l]).
Final scaling by F_SCALE = 1441 = R²·128⁻¹ mod q.