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Split prove function. #634

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May 29, 2024
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Split prove function. #634

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88 changes: 53 additions & 35 deletions crates/prover/src/core/prover/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ use super::backend::Backend;
use super::fri::FriVerificationError;
use super::pcs::{CommitmentSchemeProof, TreeVec};
use super::poly::circle::{CanonicCoset, SecureCirclePoly, MAX_CIRCLE_DOMAIN_LOG_SIZE};
use super::poly::twiddles::TwiddleTree;
use super::proof_of_work::ProofOfWorkVerificationError;
use super::ColumnVec;
use crate::core::air::{Air, AirExt, AirProverExt};
Expand Down Expand Up @@ -48,51 +49,32 @@ pub struct AdditionalProofData {
pub oods_quotients: Vec<CircleEvaluation<CpuBackend, SecureField, BitReversedOrder>>,
}

pub fn prove<B: Backend + MerkleOps<MerkleHasher>>(
air: &impl AirProver<B>,
pub fn evaluate_and_commit_on_trace<B: Backend + MerkleOps<MerkleHasher>>(
channel: &mut Channel,
twiddles: &TwiddleTree<B>,
trace: ColumnVec<CircleEvaluation<B, BaseField, BitReversedOrder>>,
) -> Result<StarkProof, ProvingError> {
// Check that traces are not too big.
for (i, trace) in trace.iter().enumerate() {
if trace.domain.log_size() + LOG_BLOWUP_FACTOR > MAX_CIRCLE_DOMAIN_LOG_SIZE {
return Err(ProvingError::MaxTraceDegreeExceeded {
trace_index: i,
degree: trace.domain.log_size(),
});
}
}

// Check that the composition polynomial is not too big.
let composition_polynomial_log_degree_bound = air.composition_log_degree_bound();
if composition_polynomial_log_degree_bound + LOG_BLOWUP_FACTOR > MAX_CIRCLE_DOMAIN_LOG_SIZE {
return Err(ProvingError::MaxCompositionDegreeExceeded {
degree: composition_polynomial_log_degree_bound,
});
}

let span = span!(Level::INFO, "Precompute twiddle").entered();
let twiddles = B::precompute_twiddles(
CanonicCoset::new(air.composition_log_degree_bound() + LOG_BLOWUP_FACTOR)
.circle_domain()
.half_coset,
);
span.exit();

// Evaluate and commit on trace.
// TODO(spapini): Commit on trace outside.
) -> Result<CommitmentSchemeProver<B>, ProvingError> {
let span = span!(Level::INFO, "Trace interpolation").entered();
let trace_polys = trace
.into_iter()
.map(|poly| poly.interpolate_with_twiddles(&twiddles))
.map(|poly| poly.interpolate_with_twiddles(twiddles))
.collect();
span.exit();

let mut commitment_scheme = CommitmentSchemeProver::new(LOG_BLOWUP_FACTOR);
let span = span!(Level::INFO, "Trace commitment").entered();
commitment_scheme.commit(trace_polys, channel, &twiddles);
commitment_scheme.commit(trace_polys, channel, twiddles);
span.exit();

Ok(commitment_scheme)
}

pub fn generate_proof<B: Backend + MerkleOps<MerkleHasher>>(
air: &impl AirProver<B>,
channel: &mut Channel,
twiddles: &TwiddleTree<B>,
commitment_scheme: &mut CommitmentSchemeProver<B>,
) -> Result<StarkProof, ProvingError> {
// Evaluate and commit on composition polynomial.
let random_coeff = channel.draw_felt();

Expand All @@ -107,7 +89,7 @@ pub fn prove<B: Backend + MerkleOps<MerkleHasher>>(
span.exit();

let span = span!(Level::INFO, "Composition commitment").entered();
commitment_scheme.commit(composition_polynomial_poly.to_vec(), channel, &twiddles);
commitment_scheme.commit(composition_polynomial_poly.to_vec(), channel, twiddles);
span.exit();

// Draw OODS point.
Expand All @@ -123,7 +105,7 @@ pub fn prove<B: Backend + MerkleOps<MerkleHasher>>(
sample_points.push(vec![vec![oods_point]; 4]);

// Prove the trace and composition OODS values, and retrieve them.
let commitment_scheme_proof = commitment_scheme.prove_values(sample_points, channel, &twiddles);
let commitment_scheme_proof = commitment_scheme.prove_values(sample_points, channel, twiddles);

// Evaluate composition polynomial at OODS point and check that it matches the trace OODS
// values. This is a sanity check.
Expand All @@ -143,6 +125,42 @@ pub fn prove<B: Backend + MerkleOps<MerkleHasher>>(
})
}

pub fn prove<B: Backend + MerkleOps<MerkleHasher>>(
air: &impl AirProver<B>,
channel: &mut Channel,
trace: ColumnVec<CircleEvaluation<B, BaseField, BitReversedOrder>>,
) -> Result<StarkProof, ProvingError> {
// Check that traces are not too big.
for (i, trace) in trace.iter().enumerate() {
if trace.domain.log_size() + LOG_BLOWUP_FACTOR > MAX_CIRCLE_DOMAIN_LOG_SIZE {
return Err(ProvingError::MaxTraceDegreeExceeded {
trace_index: i,
degree: trace.domain.log_size(),
});
}
}

// Check that the composition polynomial is not too big.
let composition_polynomial_log_degree_bound = air.composition_log_degree_bound();
if composition_polynomial_log_degree_bound + LOG_BLOWUP_FACTOR > MAX_CIRCLE_DOMAIN_LOG_SIZE {
return Err(ProvingError::MaxCompositionDegreeExceeded {
degree: composition_polynomial_log_degree_bound,
});
}

let span = span!(Level::INFO, "Precompute twiddle").entered();
let twiddles = B::precompute_twiddles(
CanonicCoset::new(air.composition_log_degree_bound() + LOG_BLOWUP_FACTOR)
.circle_domain()
.half_coset,
);
span.exit();

let mut commitment_scheme = evaluate_and_commit_on_trace(channel, &twiddles, trace)?;

generate_proof(air, channel, &twiddles, &mut commitment_scheme)
}

pub fn verify(
proof: StarkProof,
air: &impl Air,
Expand Down
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