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Create MLE eval verifier component
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andrewmilson committed Aug 28, 2024
1 parent 283d17a commit 4f24c54
Showing 1 changed file with 190 additions and 7 deletions.
197 changes: 190 additions & 7 deletions crates/prover/src/examples/xor/gkr_lookups/mle_eval.rs
Original file line number Diff line number Diff line change
Expand Up @@ -41,7 +41,7 @@ use crate::core::poly::BitReversedOrder;
use crate::core::utils::{self, bit_reverse_index, coset_index_to_circle_domain_index};
use crate::core::ColumnVec;

/// Component that carries out a univariate IOP for multilinear eval at point.
/// Prover component that carries out a univariate IOP for multilinear eval at point.
///
/// See <https://eprint.iacr.org/2023/1284.pdf> (Section 5.1).
#[allow(dead_code)]
Expand Down Expand Up @@ -101,7 +101,7 @@ impl<'twiddles, 'oracle, O: MleCoeffColumnOracle> MleEvalProverComponent<'twiddl
}
}

/// Size of this components trace columns.
/// Size of this component's trace columns.
pub fn log_size(&self) -> u32 {
self.mle_eval_point.n_variables() as u32
}
Expand Down Expand Up @@ -267,6 +267,115 @@ impl<'twiddles, 'oracle, O: MleCoeffColumnOracle> ComponentProver<SimdBackend>
}
}

/// Verifier component that carries out a univariate IOP for multilinear eval at point.
///
/// See <https://eprint.iacr.org/2023/1284.pdf> (Section 5.1).
pub struct MleEvalVerifierComponent<'oracle, O: MleCoeffColumnOracle> {
/// Oracle for the polynomial encoding the multilinear Lagrange basis coefficients of the MLE.
mle_coeff_column_oracle: &'oracle O,
/// Multilinear evaluation point.
mle_eval_point: MleEvalPoint,
/// Equals `mle_claim / 2^mle_n_variables`.
mle_claim_shift: SecureField,
/// Commitment tree index for the trace.
interaction: usize,
/// Location in the trace for the this component.
trace_location: TreeVec<TreeColumnSpan>,
}

impl<'oracle, O: MleCoeffColumnOracle> MleEvalVerifierComponent<'oracle, O> {
pub fn new(
location_allocator: &mut TraceLocationAllocator,
mle_coeff_column_oracle: &'oracle O,
eval_point: &[SecureField],
claim: SecureField,
interaction: usize,
) -> Self {
let mle_eval_point = MleEvalPoint::new(eval_point);
let n_variables = mle_eval_point.n_variables();
let mle_claim_shift = claim / BaseField::from(1 << n_variables);

let trace_structure = mle_eval_info(interaction, n_variables).mask_offsets;
let trace_location = location_allocator.next_for_structure(&trace_structure);

Self {
mle_coeff_column_oracle,
mle_eval_point,
mle_claim_shift,
interaction,
trace_location,
}
}

/// Size of this component's trace columns.
pub fn log_size(&self) -> u32 {
self.mle_eval_point.n_variables() as u32
}

pub fn eval_info(&self) -> InfoEvaluator {
let n_variables = self.mle_eval_point.n_variables();
mle_eval_info(self.interaction, n_variables)
}
}

impl<'oracle, O: MleCoeffColumnOracle> Component for MleEvalVerifierComponent<'oracle, O> {
fn n_constraints(&self) -> usize {
self.eval_info().n_constraints
}

fn max_constraint_log_degree_bound(&self) -> u32 {
self.log_size() + 1
}

fn trace_log_degree_bounds(&self) -> TreeVec<ColumnVec<u32>> {
let log_size = self.log_size();
let InfoEvaluator { mask_offsets, .. } = self.eval_info();
mask_offsets.map(|tree_offsets| vec![log_size; tree_offsets.len()])
}

fn mask_points(
&self,
point: CirclePoint<SecureField>,
) -> TreeVec<ColumnVec<Vec<CirclePoint<SecureField>>>> {
let trace_step = CanonicCoset::new(self.log_size()).step();
let InfoEvaluator { mask_offsets, .. } = self.eval_info();
mask_offsets.map_cols(|col_offsets| {
col_offsets
.iter()
.map(|offset| point + trace_step.mul_signed(*offset).into_ef())
.collect()
})
}

fn evaluate_constraint_quotients_at_point(
&self,
point: CirclePoint<SecureField>,
mask: &TreeVec<ColumnVec<Vec<SecureField>>>,
accumulator: &mut PointEvaluationAccumulator,
) {
let component_mask = mask.sub_tree(&self.trace_location);
let trace_coset = CanonicCoset::new(self.log_size()).coset;
let vanish_on_trace_eval_inv = coset_vanishing(trace_coset, point).inverse();
let mut eval = PointEvaluator::new(component_mask, accumulator, vanish_on_trace_eval_inv);

let mle_coeff_col_eval = self.mle_coeff_column_oracle.evaluate_at_point(point, mask);
let carry_quotients_col_eval = eval_carry_quotient_col(&self.mle_eval_point, point);
let is_first = eval_is_first(trace_coset, point);
let is_second = eval_is_first(trace_coset, point - trace_coset.step.into_ef());

eval_mle_eval_constraints(
self.interaction,
&mut eval,
mle_coeff_col_eval,
&self.mle_eval_point,
self.mle_claim_shift,
carry_quotients_col_eval,
is_first,
is_second,
)
}
}

fn mle_eval_info(interaction: usize, n_variables: usize) -> InfoEvaluator {
let mut eval = InfoEvaluator::default();
let mle_eval_point = MleEvalPoint::new(&vec![SecureField::from(2); n_variables]);
Expand Down Expand Up @@ -613,8 +722,9 @@ mod tests {
use rand::{Rng, SeedableRng};

use super::{
eval_carry_quotient_col, eval_eq_constraints, eval_mle_eval_constraints,
eval_prefix_sum_constraints, gen_carry_quotient_col, MleEvalPoint,
build_trace, eval_carry_quotient_col, eval_eq_constraints, eval_mle_eval_constraints,
eval_prefix_sum_constraints, gen_carry_quotient_col, MleEvalPoint, MleEvalProverComponent,
MleEvalVerifierComponent,
};
use crate::constraint_framework::constant_columns::{gen_is_first, gen_is_step_with_offset};
use crate::constraint_framework::{assert_constraints, EvalAtRow, TraceLocationAllocator};
Expand All @@ -635,9 +745,7 @@ mod tests {
use crate::core::utils::{bit_reverse, coset_order_to_circle_domain_order};
use crate::core::vcs::blake2_merkle::Blake2sMerkleChannel;
use crate::examples::xor::gkr_lookups::accumulation::MIN_LOG_BLOWUP_FACTOR;
use crate::examples::xor::gkr_lookups::mle_eval::{
build_trace, eval_step_selector_with_offset, MleEvalProverComponent,
};
use crate::examples::xor::gkr_lookups::mle_eval::eval_step_selector_with_offset;

#[test]
fn mle_eval_prover_component() -> Result<(), VerificationError> {
Expand Down Expand Up @@ -701,6 +809,81 @@ mod tests {
verify(&components.0, channel, commitment_scheme, proof)
}

#[test]
fn mle_eval_verifier_component() -> Result<(), VerificationError> {
const N_VARIABLES: usize = 8;
const COEFFS_COL_TRACE: usize = 0;
const MLE_EVAL_TRACE: usize = 1;
const CONST_TRACE: usize = 2;
const LOG_EXPAND: u32 = 1;
// Create the test MLE.
let mut rng = SmallRng::seed_from_u64(0);
let log_size = N_VARIABLES as u32;
let size = 1 << log_size;
let mle_coeffs = (0..size).map(|_| rng.gen::<SecureField>()).collect();
let mle = Mle::<SimdBackend, SecureField>::new(mle_coeffs);
let eval_point: [SecureField; N_VARIABLES] = array::from_fn(|_| rng.gen());
let claim = mle.eval_at_point(&eval_point);
// Setup protocol.
let twiddles = SimdBackend::precompute_twiddles(
CanonicCoset::new(log_size + LOG_EXPAND + MIN_LOG_BLOWUP_FACTOR)
.circle_domain()
.half_coset,
);
let config = PcsConfig::default();
let commitment_scheme = &mut CommitmentSchemeProver::new(config, &twiddles);
let channel = &mut Blake2sChannel::default();
// Build trace.
// 1. MLE coeffs trace.
let mut tree_builder = commitment_scheme.tree_builder();
tree_builder.extend_evals(mle_coeff_column::build_trace(&mle));
tree_builder.commit(channel);
// 2. MLE eval trace (eq evals + prefix sum).
let mut tree_builder = commitment_scheme.tree_builder();
tree_builder.extend_evals(build_trace(&mle, &eval_point, claim));
tree_builder.commit(channel);
// Create components.
let trace_location_allocator = &mut TraceLocationAllocator::default();
let mle_coeffs_col_component = MleCoeffColumnComponent::new(
trace_location_allocator,
MleCoeffColumnEval::new(COEFFS_COL_TRACE, mle.n_variables()),
);
let mle_eval_component = MleEvalProverComponent::generate(
trace_location_allocator,
&mle_coeffs_col_component,
&eval_point,
mle,
claim,
&twiddles,
MLE_EVAL_TRACE,
);
let components: &[&dyn ComponentProver<SimdBackend>] =
&[&mle_coeffs_col_component, &mle_eval_component];
// Generate proof.
let proof = prove(components, channel, commitment_scheme).unwrap();

// Verify.
let trace_location_allocator = &mut TraceLocationAllocator::default();
let mle_coeffs_col_component = MleCoeffColumnComponent::new(
trace_location_allocator,
MleCoeffColumnEval::new(COEFFS_COL_TRACE, N_VARIABLES),
);
let mle_eval_component = MleEvalVerifierComponent::new(
trace_location_allocator,
&mle_coeffs_col_component,
&eval_point,
claim,
MLE_EVAL_TRACE,
);
let components = Components(vec![&mle_coeffs_col_component, &mle_eval_component]);
let log_sizes = components.column_log_sizes();
let channel = &mut Blake2sChannel::default();
let commitment_scheme = &mut CommitmentSchemeVerifier::<Blake2sMerkleChannel>::new(config);
commitment_scheme.commit(proof.commitments[0], &log_sizes[0], channel);
commitment_scheme.commit(proof.commitments[1], &log_sizes[1], channel);
verify(&components.0, channel, commitment_scheme, proof)
}

#[test]
fn test_mle_eval_constraints_with_log_size_5() {
const N_VARIABLES: usize = 5;
Expand Down

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