ligerito 0.6.2

Ligerito polynomial commitment scheme over binary extension fields
Documentation 
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#[cfg(feature = "prover")]
use crate::data_structures::RecursiveLigeroWitness;
use crate::utils::{eval_sk_at_vks, evaluate_lagrange_basis, evaluate_scaled_basis_inplace};
use binary_fields::{BinaryFieldElement, BinaryPolynomial};
use merkle_tree::{build_merkle_tree, Hash};
#[cfg(feature = "parallel")]
use rayon::prelude::*;
#[cfg(feature = "prover")]
use reed_solomon::ReedSolomon;
use sha2::{Digest, Sha256};

// Debug printing macros - no-ops in no_std
#[cfg(feature = "std")]
macro_rules! debug_println {
    ($($arg:tt)*) => { std::println!($($arg)*) }
}

#[cfg(not(feature = "std"))]
macro_rules! debug_println {
    ($($arg:tt)*) => {};
}

#[cfg(feature = "prover")]
pub fn poly2mat<F: BinaryFieldElement>(
    poly: &[F],
    m: usize,
    n: usize,
    inv_rate: usize,
) -> Vec<Vec<F>> {
    let m_target = m * inv_rate;
    let mut mat = vec![vec![F::zero(); n]; m_target];

    #[cfg(feature = "parallel")]
    {
        mat.par_iter_mut().enumerate().for_each(|(i, row)| {
            for j in 0..n {
                let idx = j * m + i;
                if idx < poly.len() {
                    row[j] = poly[idx];
                }
            }
        });
    }

    #[cfg(not(feature = "parallel"))]
    {
        for (i, row) in mat.iter_mut().enumerate() {
            for j in 0..n {
                let idx = j * m + i;
                if idx < poly.len() {
                    row[j] = poly[idx];
                }
            }
        }
    }

    mat
}

#[cfg(all(feature = "prover", feature = "parallel"))]
pub fn encode_cols<F: BinaryFieldElement + Send + Sync + bytemuck::Pod + 'static>(
    poly_mat: &mut Vec<Vec<F>>,
    rs: &ReedSolomon<F>,
    parallel: bool,
) {
    let n = poly_mat[0].len();

    if parallel {
        // Parallelize at column level only - each column FFT runs sequentially
        // to avoid nested parallelization overhead
        let cols: Vec<Vec<F>> = (0..n)
            .into_par_iter()
            .map(|j| {
                let mut col: Vec<F> = poly_mat.iter().map(|row| row[j]).collect();
                // Use sequential FFT within each parallel task to avoid nested parallelism
                reed_solomon::encode_in_place_with_parallel(rs, &mut col, false);
                col
            })
            .collect();

        // Transpose back
        for (i, row) in poly_mat.iter_mut().enumerate() {
            for (j, col) in cols.iter().enumerate() {
                row[j] = col[i];
            }
        }
    } else {
        for j in 0..n {
            let mut col: Vec<F> = poly_mat.iter().map(|row| row[j]).collect();
            reed_solomon::encode_in_place(rs, &mut col);
            for (i, val) in col.iter().enumerate() {
                poly_mat[i][j] = *val;
            }
        }
    }
}

#[cfg(all(feature = "prover", not(feature = "parallel")))]
pub fn encode_cols<F: BinaryFieldElement + Send + Sync + bytemuck::Pod + 'static>(
    poly_mat: &mut Vec<Vec<F>>,
    rs: &ReedSolomon<F>,
    _parallel: bool,
) {
    let n = poly_mat[0].len();
    for j in 0..n {
        let mut col: Vec<F> = poly_mat.iter().map(|row| row[j]).collect();
        reed_solomon::encode_in_place(rs, &mut col);
        for (i, val) in col.iter().enumerate() {
            poly_mat[i][j] = *val;
        }
    }
}

/// Hash a row of field elements with deterministic serialization
/// Optimized: hashes entire row at once instead of element-by-element
#[inline(always)]
pub fn hash_row<F: BinaryFieldElement>(row: &[F]) -> Hash {
    let mut hasher = Sha256::new();

    // Hash row length for domain separation
    hasher.update((row.len() as u32).to_le_bytes());

    // Hash entire row at once using bytemuck for zero-copy byte slice
    // This is much faster than per-element hashing
    let row_bytes = unsafe {
        core::slice::from_raw_parts(row.as_ptr() as *const u8, std::mem::size_of_val(row))
    };
    hasher.update(row_bytes);

    hasher.finalize().into()
}

#[cfg(feature = "prover")]
pub fn ligero_commit<F: BinaryFieldElement + Send + Sync + bytemuck::Pod + 'static>(
    poly: &[F],
    m: usize,
    n: usize,
    rs: &ReedSolomon<F>,
) -> RecursiveLigeroWitness<F> {
    let mut poly_mat = poly2mat(poly, m, n, 4);

    // Direct call - no backend abstraction overhead
    encode_cols(&mut poly_mat, rs, true);

    // Parallelize row hashing
    #[cfg(feature = "parallel")]
    let hashed_rows: Vec<Hash> = poly_mat.par_iter().map(|row| hash_row(row)).collect();

    #[cfg(not(feature = "parallel"))]
    let hashed_rows: Vec<Hash> = poly_mat.iter().map(|row| hash_row(row)).collect();

    let tree = build_merkle_tree(&hashed_rows);

    RecursiveLigeroWitness {
        mat: poly_mat,
        tree,
    }
}

pub fn verify_ligero<T, U>(queries: &[usize], opened_rows: &[Vec<T>], yr: &[T], challenges: &[U])
where
    T: BinaryFieldElement + Send + Sync,
    U: BinaryFieldElement + Send + Sync + From<T>,
{
    debug_println!("verify_ligero: challenges = {:?}", challenges);

    let gr = evaluate_lagrange_basis(challenges);
    let n = yr.len().trailing_zeros() as usize;

    // Julia uses eval_sk_at_vks(2^n, U) but also has T for yr
    // We need sks_vks in type T to match yr
    let sks_vks: Vec<T> = eval_sk_at_vks(1 << n);

    // Let's test the first query only to avoid too much output
    if !queries.is_empty() {
        let query = queries[0];
        let row = &opened_rows[query];

        let dot = row.iter().zip(gr.iter()).fold(U::zero(), |acc, (&r, &g)| {
            let r_u = U::from(r);
            acc.add(&r_u.mul(&g))
        });

        // Convert query index to field element correctly
        // julia uses T(query - 1) because julia queries are 1-based
        // rust queries are already 0-based, so use query directly
        let query_for_basis = query % (1 << n);
        let qf = T::from_poly(<T as BinaryFieldElement>::Poly::from_value(
            query_for_basis as u64,
        ));

        let mut local_sks_x = vec![T::zero(); sks_vks.len()];
        let mut local_basis = vec![U::zero(); 1 << n];
        let scale = U::from(T::one());
        evaluate_scaled_basis_inplace(&mut local_sks_x, &mut local_basis, &sks_vks, qf, scale);

        let e = yr
            .iter()
            .zip(local_basis.iter())
            .fold(U::zero(), |acc, (&y, &b)| {
                let y_u = U::from(y);
                acc.add(&y_u.mul(&b))
            });

        debug_println!(
            "verify_ligero: Query {} -> e = {:?}, dot = {:?}",
            query,
            e,
            dot
        );
        debug_println!("verify_ligero: Equal? {}", e == dot);

        if e != dot {
            debug_println!(
                "verify_ligero: mathematical relationship mismatch for query {}",
                query
            );
            debug_println!("  e = {:?}", e);
            debug_println!("  dot = {:?}", dot);
            debug_println!("  this might be expected in certain contexts");
            // don't panic - this might be normal behavior in some verification contexts
        } else {
            debug_println!(
                "verify_ligero: mathematical relationship holds for query {}",
                query
            );
        }
    }
}