Struct Ntt64Context 

pub struct Ntt64Context {
    pub n: usize,
    pub log_n: u32,
    pub arith: Ntt64Arith,
    pub root_powers: Vec<u64>,
    pub inv_root_powers: Vec<u64>,
    pub n_inv: u64,
}

Precomputed NTT context for a given (N, modulus) pair.

Contains twiddle-factor tables for both forward and inverse NTT, organized in Longa-Naehrig ordering for negacyclic convolution.

Fields

n: usize

Polynomial size (power of 2).

log_n: u32

log₂(n).

arith: Ntt64Arith

Modular arithmetic context (Barrett/Montgomery constants).

root_powers: Vec<u64>

Twiddle factors for forward NTT.

Organized for sequential access in the Cooley-Tukey butterfly: root_powers[m + j] for layer with half-size m and group index j.

inv_root_powers: Vec<u64>

Inverse twiddle factors for inverse NTT.

Organized for sequential access in the Gentleman-Sande butterfly.

n_inv: u64

N⁻¹ mod q — normalization factor for the INTT.

Implementations

impl Ntt64Context

pub fn try_new(n: usize, arith: Ntt64Arith) -> Result<Self, NttError>

Fallible constructor for an NTT context.

Validates all preconditions and returns an error instead of panicking.

Arguments

• n — polynomial size, must be a power of 2 (≥ 2)
• arith — precomputed modular arithmetic context; the modulus must be prime and satisfy q ≡ 1 (mod 2N)

Errors

• crate::NttError::InvalidSize if n is not a power of 2 ≥ 2
• crate::NttError::NotPrime if the modulus is not prime
• crate::NttError::NotNttFriendly if q − 1 is not divisible by 2N

pub fn new(n: usize, arith: Ntt64Arith) -> Self

Creates a new NTT context for polynomial size n and the given arithmetic context.

Arguments

• n — polynomial size, must be a power of 2 (≥ 2)
• arith — precomputed modular arithmetic context; the modulus must satisfy q ≡ 1 (mod 2N)

Panics

• If n is not a power of 2
• If the modulus is not prime
• If q − 1 is not divisible by 2N

pub fn forward(&self, data: &mut [u64])

Applies forward NTT in-place.

pub fn inverse(&self, data: &mut [u64])

Applies inverse NTT in-place.

pub fn forward_tiled(&self, data: &mut [u64])

Applies the tiled forward NTT in-place.

Currently delegates to the standard forward NTT. A cache-optimized four-step variant is planned for v0.2.

pub fn pointwise_mul(&self, a: &[u64], b: &[u64], result: &mut [u64])

Pointwise multiplication of two NTT-domain vectors.

result[i] = a[i] * b[i] mod q

This is the core operation: in NTT domain, polynomial convolution becomes element-wise multiplication.

pub fn negacyclic_mul(&self, a: &[u64], b: &[u64]) -> Vec<u64>

Full negacyclic polynomial multiplication: c = a * b mod (X^N + 1).

Performs forward NTT on both inputs, pointwise multiplication, and inverse NTT on the result.

Trait Implementations

impl Clone for Ntt64Context

fn clone(&self) -> Ntt64Context

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Ntt64Context

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.