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Merge pull request #604 from mir-protocol/get_subgroup_evals

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Use FFTs to get subgroup evaluations in `check_constraints`
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Daniel Lubarov 2022-07-13 09:52:14 -07:00 committed by GitHub
commit c214c53c93
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1 changed files with 17 additions and 19 deletions
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36
evm/src/prover.rs
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@ -492,14 +492,19 @@ fn check_constraints<'a, F, C, S, const D: usize>(
let subgroup = F::two_adic_subgroup(degree_bits + rate_bits);
// Retrieve the polynomials values at index `i`.
let get_comm_values = |comm: &PolynomialBatch<F, C, D>, i| -> Vec<F> {
comm.polynomials
.iter()
.map(|poly| poly.eval(subgroup[i])) // O(n^2) FTW
.collect()
// Get the evaluations of a batch of polynomials over our subgroup.
let get_subgroup_evals = |comm: &PolynomialBatch<F, C, D>| -> Vec<Vec<F>> {
let values = comm
.polynomials
.par_iter()
.map(|coeffs| coeffs.clone().fft().values)
.collect::<Vec<_>>();
transpose(&values)
};
let trace_subgroup_evals = get_subgroup_evals(trace_commitment);
let permutation_ctl_zs_subgroup_evals = get_subgroup_evals(permutation_ctl_zs_commitment);
// Last element of the subgroup.
let last = F::primitive_root_of_unity(degree_bits).inverse();
@ -519,19 +524,14 @@ fn check_constraints<'a, F, C, S, const D: usize>(
lagrange_basis_last,
);
let vars = StarkEvaluationVars {
local_values: &get_comm_values(trace_commitment, i).try_into().unwrap(),
next_values: &get_comm_values(trace_commitment, i_next)
.try_into()
.unwrap(),
local_values: trace_subgroup_evals[i].as_slice().try_into().unwrap(),
next_values: trace_subgroup_evals[i_next].as_slice().try_into().unwrap(),
public_inputs: &public_inputs,
};
let permutation_check_vars =
permutation_challenges.map(|permutation_challenge_sets| PermutationCheckVars {
local_zs: get_comm_values(permutation_ctl_zs_commitment, i)
[..num_permutation_zs]
.to_vec(),
next_zs: get_comm_values(permutation_ctl_zs_commitment, i_next)
[..num_permutation_zs]
local_zs: permutation_ctl_zs_subgroup_evals[i][..num_permutation_zs].to_vec(),
next_zs: permutation_ctl_zs_subgroup_evals[i_next][..num_permutation_zs]
.to_vec(),
permutation_challenge_sets: permutation_challenge_sets.to_vec(),
});
@ -542,10 +542,8 @@ fn check_constraints<'a, F, C, S, const D: usize>(
.enumerate()
.map(
|(iii, (_, columns, filter_column))| CtlCheckVars::<F, F, F, 1> {
local_z: get_comm_values(permutation_ctl_zs_commitment, i)
[num_permutation_zs + iii],
next_z: get_comm_values(permutation_ctl_zs_commitment, i_next)
[num_permutation_zs + iii],
local_z: permutation_ctl_zs_subgroup_evals[i][num_permutation_zs + iii],
next_z: permutation_ctl_zs_subgroup_evals[i_next][num_permutation_zs + iii],
challenges: ctl_data.challenges.challenges[iii % config.num_challenges],
columns,
filter_column,