Struct NTTLookup 

pub struct NTTLookup(/* private fields */);

A precomputed lookup table for fast LDE operations on 64-bit binary field elements.

This structure stores precomputed LDE evaluations for all possible 8-bit input combinations, enabling fast computation of the full 64-bit LDE through table lookups and additions. See the module-level documentation for the LDE definition and the Flock compression it uses.

Structure

The internal data structure is a boxed array Box<[[PackedRijndael64x8b; 256]; 2]> where:

• First dimension: the byte-position parity b % 2. Only these two tables are stored; the remaining six byte positions are recovered by permutation (see the module-level “Compressed storage” notes).
• Second dimension: the 8-bit value (0-255) for that byte.

Each entry holds the ROWS_PER_HYPERCUBE_VERTEX LDE evaluations of that byte’s coefficients, packed into a single PackedRijndael64x8b.

Implementations

impl NTTLookup

pub fn new(subspace: &BinarySubspace<B8>) -> Self

Creates a new NTT lookup table by precomputing all possible NTT evaluations for 8-bit input chunks across all byte positions in a 64-bit word.

Parameters

• subspace: Binary subspace of dimension SKIPPED_VARS + 1. Its lower half defines the NTT input domain and its upper half the output domain at which evaluations are precomputed.

Constraints

• Subspace dimension must equal SKIPPED_VARS + 1

Panics

Panics if subspace.dim() != SKIPPED_VARS + 1.

pub fn ntt(&self, input: Word) -> PackedRijndael64x8b

Computes the LDE of 64 1-bit coefficients using the precomputed lookup tables.

The 64-bit input is split into eight bytes B₀, B₁, …, B₇. By linearity the LDE of the input is the sum of the per-byte LDEs: LDE(input) = LDE(B₀) + LDE(B₁) + ... + LDE(B₇).

Only two byte-position tables are stored, so the LDE of byte position b is reconstructed from the table for parity b % 2 by permuting its packed evaluations according to b / 2. This permutation is the translation of the output domain exploited by the Flock compression (see the module-level “Compressed storage” notes); in the packed representation it is a permutation of the four 128-bit lanes, lane[i] <- lane[i ^ (b / 2)]. The loop is unrolled over b, so the parity select and lane index are compile-time constants.

Used directly only in tests; univariate_round_message_extension_domain accesses the tables inline to compute three LDE evaluations at once, which is more efficient.

Returns

A PackedRijndael64x8b holding the ROWS_PER_HYPERCUBE_VERTEX LDE evaluations over the output domain.

Trait Implementations

impl Clone for NTTLookup

fn clone(&self) -> NTTLookup

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for NTTLookup

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

Formats the value using the given formatter.