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Optimize prover boundary evaluations in construction of composition polynomial #22

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merged 5 commits into from
Jun 6, 2023
Merged

Optimize prover boundary evaluations in construction of composition polynomial #22

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a042ae0
Compute boundary evaluations and batch inverse of zerofier outside of…
ajgara Jun 5, 2023
dcb945b
Clippy and format
ajgara Jun 5, 2023
03dc0ba
Merge branch 'main' into optimize-prover-boundary-evaluations
schouhy Jun 6, 2023
aff667a
evaluate boundary polys before collecting the polynomials
schouhy Jun 6, 2023
9cb5dad
add space
schouhy Jun 6, 2023
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56 changes: 46 additions & 10 deletions src/air/constraints/evaluator.rs
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,11 @@ use lambdaworks_math::{
};

use super::{boundary::BoundaryConstraints, evaluation_table::ConstraintEvaluationTable};
use crate::air::{frame::Frame, trace::TraceTable, AIR};
use crate::{
air::{frame::Frame, trace::TraceTable, AIR},
prover::evaluate_polynomial_on_lde_domain,
Domain,
};
use std::iter::zip;

pub struct ConstraintEvaluator<'poly, F: IsFFTField, A: AIR> {
Expand Down Expand Up @@ -36,7 +40,7 @@ impl<'poly, F: IsFFTField, A: AIR + AIR<Field = F>> ConstraintEvaluator<'poly, F
pub fn evaluate(
&self,
lde_trace: &TraceTable<F>,
lde_domain: &[FieldElement<F>],
domain: &Domain<F>,
alpha_and_beta_transition_coefficients: &[(FieldElement<F>, FieldElement<F>)],
alpha_and_beta_boundary_coefficients: &[(FieldElement<F>, FieldElement<F>)],
rap_challenges: &A::RAPChallenges,
Expand All @@ -47,7 +51,7 @@ impl<'poly, F: IsFFTField, A: AIR + AIR<Field = F>> ConstraintEvaluator<'poly, F
// The + 1 is for the boundary constraints column
let mut evaluation_table = ConstraintEvaluationTable::new(
self.air.context().num_transition_constraints() + 1,
lde_domain,
&domain.lde_roots_of_unity_coset,
);
let n_trace_colums = self.trace_polys.len();
let boundary_constraints = &self.boundary_constraints;
Expand Down Expand Up @@ -83,11 +87,37 @@ impl<'poly, F: IsFFTField, A: AIR + AIR<Field = F>> ConstraintEvaluator<'poly, F
#[cfg(debug_assertions)]
let mut transition_evaluations = Vec::new();

let mut boundary_polys_evaluations = Vec::with_capacity(boundary_polys.len());
for poly in boundary_polys.iter() {
let evaluations = evaluate_polynomial_on_lde_domain(
poly,
domain.blowup_factor,
domain.interpolation_domain_size,
&domain.coset_offset,
)
.unwrap();
boundary_polys_evaluations.push(evaluations);
}

let mut boundary_zerofiers_inverse_evaluations =
Vec::with_capacity(boundary_zerofiers.len());
for poly in boundary_zerofiers.iter() {
let mut evaluations = evaluate_polynomial_on_lde_domain(
poly,
domain.blowup_factor,
domain.interpolation_domain_size,
&domain.coset_offset,
)
.unwrap();
FieldElement::inplace_batch_inverse(&mut evaluations);
boundary_zerofiers_inverse_evaluations.push(evaluations);
}
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We can evaluate the polynomials before collecting the original vectors, so we halve the memory taken by the whole operation.

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Good idea. Done!


let divisors = self.air.transition_divisors();
let boundary_term_degree_adjustment =
self.air.composition_poly_degree_bound() - self.air.context().trace_length;
// Iterate over trace and domain and compute transitions
for (i, d) in lde_domain.iter().enumerate() {
for (i, d) in domain.lde_roots_of_unity_coset.iter().enumerate() {
let frame = Frame::read_from_trace(
lde_trace,
i,
Expand All @@ -109,16 +139,22 @@ impl<'poly, F: IsFFTField, A: AIR + AIR<Field = F>> ConstraintEvaluator<'poly, F
);

let d_adjustment_power = d.pow(boundary_term_degree_adjustment);
let boundary_evaluation = zip(&boundary_polys, &boundary_zerofiers)
.enumerate()
.map(|(index, (boundary_poly, boundary_zerofier))| {
let boundary_evaluation = zip(
&boundary_polys_evaluations,
&boundary_zerofiers_inverse_evaluations,
)
.enumerate()
.map(
|(index, (boundary_poly_evaluation, zerofier_inverse_evaluation))| {
let (boundary_alpha, boundary_beta) =
alpha_and_beta_boundary_coefficients[index].clone();

(boundary_poly.evaluate(d) / boundary_zerofier.evaluate(d))
&boundary_poly_evaluation[i]
* &zerofier_inverse_evaluation[i]
* (&boundary_alpha * &d_adjustment_power + &boundary_beta)
})
.fold(FieldElement::<F>::zero(), |acc, eval| acc + eval);
},
)
.fold(FieldElement::<F>::zero(), |acc, eval| acc + eval);

evaluations.push(boundary_evaluation);

Expand Down
4 changes: 2 additions & 2 deletions src/prover.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -91,7 +91,7 @@ where
(trees, roots)
}

fn evaluate_polynomial_on_lde_domain<F>(
pub fn evaluate_polynomial_on_lde_domain<F>(
p: &Polynomial<FieldElement<F>>,
blowup_factor: usize,
domain_size: usize,
Expand Down Expand Up @@ -224,7 +224,7 @@ where

let constraint_evaluations = evaluator.evaluate(
&round_1_result.lde_trace,
&domain.lde_roots_of_unity_coset,
domain,
transition_coeffs,
boundary_coeffs,
&round_1_result.rap_challenges,
Expand Down