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Merged
merged 2 commits into from
Jun 19, 2025
Merged

Feat: combine multiple loops into one in sumcheck verifier #22

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64f8730
combine two phases into one to reduce memory rw cost
kunxian-xia Jun 19, 2025
b7eb655
save 3 cycles by using 0+0 trick
kunxian-xia Jun 19, 2025
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2 changes: 1 addition & 1 deletion src/arithmetics/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -724,7 +724,7 @@ impl<C: Config> UniPolyExtrapolator<C> {
}

pub fn extrapolate_uni_poly(&mut self, builder: &mut Builder<C>, p_i: &Array<C, Ext<C::F, C::EF>>, eval_at: Ext<C::F, C::EF>) -> Ext<C::F, C::EF> {
let res: Ext<C::F, C::EF> = builder.constant(C::EF::ZERO);
let res: Ext<C::F, C::EF> = builder.eval(self.constants[0] + self.constants[0]);

builder.if_eq(p_i.len(), Usize::from(4)).then_or_else(|builder| {
let ext = self.extrapolate_uni_poly_deg_3(builder, p_i, eval_at);
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72 changes: 22 additions & 50 deletions src/tower_verifier/program.rs
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Expand Up @@ -2,7 +2,8 @@ use super::binding::{
IOPProverMessageVariable, PointAndEvalVariable, PointVariable, TowerVerifierInputVariable,
};
use crate::arithmetics::{
challenger_multi_observe, dot_product, eq_eval, evaluate_at_point, extend, exts_to_felts, fixed_dot_product, gen_alpha_pows, is_smaller_than, reverse, UniPolyExtrapolator
challenger_multi_observe, dot_product, eq_eval, evaluate_at_point, extend, exts_to_felts,
fixed_dot_product, gen_alpha_pows, is_smaller_than, reverse, UniPolyExtrapolator,
};
use crate::transcript::transcript_observe_label;
use openvm_native_compiler::prelude::*;
Expand Down Expand Up @@ -70,83 +71,54 @@ pub fn iop_verifier_state_verify<C: Config>(
Array<C, Ext<<C as Config>::F, <C as Config>::EF>>,
Ext<<C as Config>::F, <C as Config>::EF>,
) {
// TODO: either store it in a global cache or pass them as parameters
let zero: Ext<C::F, C::EF> = builder.constant(C::EF::ZERO);

let max_num_variables_usize: Usize<C::N> =
Usize::from(builder.cast_felt_to_var(max_num_variables.clone()));
challenger.observe(builder, max_num_variables);
challenger.observe(builder, max_degree);

let one: Ext<C::F, C::EF> = builder.constant(C::EF::ONE);
let round: Ext<C::F, C::EF> = builder.constant(C::EF::ONE);
builder.assert_var_eq(max_num_variables_usize.get_var(), prover_messages.len());

let challenges: Array<C, Ext<C::F, C::EF>> = builder.dyn_array(max_num_variables_usize.clone());
let expected: Ext<C::F, C::EF> = builder.eval(out_claim.clone() + zero);

builder.cycle_tracker_start("IOPVerifierState::verify_round_and_update_state");
builder
.range(0, max_num_variables_usize.clone())
.for_each(|i_vec, builder| {
let i = i_vec[0];
// TODO: this takes 7 cycles, can we optimize it?
let prover_msg = builder.get(&prover_messages, i);

builder.cycle_tracker_start("multi_observe");
builder.cycle_tracker_start("observe_then_sample");
unsafe {
let prover_msg_felts = exts_to_felts(builder, &prover_msg.evaluations);
challenger_multi_observe(builder, challenger, &prover_msg_felts);
}
builder.cycle_tracker_end("multi_observe");

builder.cycle_tracker_start("observe round");
transcript_observe_label(builder, challenger, b"Internal round");
builder.cycle_tracker_end("observe round");

builder.cycle_tracker_start("sample_ext");
let challenge = challenger.sample_ext(builder);
builder.cycle_tracker_end("sample_ext");

builder.set_value(&challenges, i, challenge);
builder.assign(&round, round + one);
});
builder.cycle_tracker_end("IOPVerifierState::verify_round_and_update_state");

builder.cycle_tracker_start("IOPVerifierState::check_and_generate_subclaim");
// set `expected` to P(r)`
let expected_len: RVar<_> = builder.eval_expr(max_num_variables_usize.clone() + RVar::from(1));
let expected_vec: Array<C, Ext<C::F, C::EF>> = builder.dyn_array(expected_len.clone());
builder.set(&expected_vec, 0, out_claim.clone());
builder.cycle_tracker_end("observe_then_sample");

let truncated_expected_vec = expected_vec.slice(builder, 1, expected_len);
iter_zip!(builder, prover_messages, challenges, truncated_expected_vec).for_each(
|idx_vec, builder| {
let poly_ptr = idx_vec[0];
let c_ptr = idx_vec[1];
let e1 = builder.get(&prover_msg.evaluations, 0);
let e2 = builder.get(&prover_msg.evaluations, 1);
let target: Ext<<C as Config>::F, <C as Config>::EF> = builder.eval(e1 + e2);
builder.assert_ext_eq(expected, target);

let msg = builder.iter_ptr_get(&prover_messages, poly_ptr);
let c = builder.iter_ptr_get(&challenges, c_ptr);

let expected_ptr = idx_vec[2];
builder.cycle_tracker_start("extrapolate_uni_poly");
let expected = unipoly_extrapolator.extrapolate_uni_poly(
let p_r = unipoly_extrapolator.extrapolate_uni_poly(
builder,
&msg.evaluations,
c,
&prover_msg.evaluations,
challenge,
);
builder.cycle_tracker_end("extrapolate_uni_poly");
builder.iter_ptr_set(&truncated_expected_vec, expected_ptr, expected);
},
);

// l-append asserted_sum to the first position of the expected vector
iter_zip!(builder, prover_messages, expected_vec).for_each(|idx_vec, builder| {
let msg = builder.iter_ptr_get(&prover_messages, idx_vec[0]);
let expected = builder.iter_ptr_get(&expected_vec, idx_vec[1]);

let e1 = builder.get(&msg.evaluations, 0);
let e2 = builder.get(&msg.evaluations, 1);
let target: Ext<<C as Config>::F, <C as Config>::EF> = builder.eval(e1 + e2);

builder.assert_ext_eq(expected, target);
});

let expected = builder.get(&expected_vec, max_num_variables_usize);
builder.cycle_tracker_end("IOPVerifierState::check_and_generate_subclaim");
builder.assign(&expected, p_r + zero);
builder.set_value(&challenges, i, challenge);
});
builder.cycle_tracker_end("IOPVerifierState::verify_round_and_update_state");

(challenges, expected)
}
Expand Down