stwo 1.0.0

Stwo Circle-STARKs prover
Documentation 
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use itertools::Itertools;

use super::CpuBackend;
use crate::core::fields::m31::BaseField;
use crate::core::fields::qm31::SecureField;
use crate::core::pcs::quotients::{
    accumulate_row_quotients, quotient_constants, ColumnSampleBatch,
};
use crate::core::poly::circle::CircleDomain;
use crate::core::utils::bit_reverse_index;
use crate::prover::poly::circle::{CircleEvaluation, SecureEvaluation};
use crate::prover::poly::BitReversedOrder;
use crate::prover::secure_column::SecureColumnByCoords;
use crate::prover::QuotientOps;

impl QuotientOps for CpuBackend {
    fn accumulate_quotients(
        domain: CircleDomain,
        columns: &[&CircleEvaluation<Self, BaseField, BitReversedOrder>],
        random_coeff: SecureField,
        sample_batches: &[ColumnSampleBatch],
        _log_blowup_factor: u32,
    ) -> SecureEvaluation<Self, BitReversedOrder> {
        let mut values = unsafe { SecureColumnByCoords::uninitialized(domain.size()) };
        let quotient_constants = quotient_constants(sample_batches, random_coeff);

        for row in 0..domain.size() {
            let domain_point = domain.at(bit_reverse_index(row, domain.log_size()));
            let query_values_at_row = columns.iter().map(|col| col[row]).collect_vec();
            let row_value = accumulate_row_quotients(
                sample_batches,
                &query_values_at_row,
                &quotient_constants,
                domain_point,
            );
            values.set(row, row_value);
        }
        SecureEvaluation::new(domain, values)
    }
}

#[cfg(test)]
mod tests {
    use crate::core::circle::SECURE_FIELD_CIRCLE_GEN;
    use crate::core::pcs::quotients::ColumnSampleBatch;
    use crate::core::poly::circle::CanonicCoset;
    use crate::prover::backend::cpu::{CpuCircleEvaluation, CpuCirclePoly};
    use crate::prover::backend::CpuBackend;
    use crate::prover::QuotientOps;
    use crate::{m31, qm31};

    #[test]
    fn test_quotients_are_low_degree() {
        const LOG_SIZE: u32 = 7;
        const LOG_BLOWUP_FACTOR: u32 = 1;
        let polynomial = CpuCirclePoly::new((0..1 << LOG_SIZE).map(|i| m31!(i)).collect());
        let eval_domain = CanonicCoset::new(LOG_SIZE + 1).circle_domain();
        let eval = polynomial.evaluate(eval_domain);
        let point = SECURE_FIELD_CIRCLE_GEN;
        let value = polynomial.eval_at_point(point);
        let coeff = qm31!(1, 2, 3, 4);
        let quot_eval = CpuBackend::accumulate_quotients(
            eval_domain,
            &[&eval],
            coeff,
            &[ColumnSampleBatch {
                point,
                columns_and_values: vec![(0, value)],
            }],
            LOG_BLOWUP_FACTOR,
        );
        let quot_poly_base_field =
            CpuCircleEvaluation::new(eval_domain, quot_eval.columns[0].clone()).interpolate();
        assert!(quot_poly_base_field.is_in_fri_space(LOG_SIZE));
    }
}