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feat: dot product when one vector's size is known #17

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Merged
merged 1 commit into from
Jun 16, 2025
Merged

feat: dot product when one vector's size is known #17

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17 changes: 17 additions & 0 deletions src/arithmetics/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -122,6 +122,23 @@ pub fn dot_product_pt_n_eval<C: Config>(
acc
}

pub fn fixed_dot_product<C: Config>(
builder: &mut Builder<C>,
a: &[Ext<C::F, C::EF>],
b: &Array<C, Ext<C::F, C::EF>>,
zero: Ext<C::F, C::EF>,
) -> Ext<<C as Config>::F, <C as Config>::EF> {
// simple trick to prefer AddE(1 cycle) than AddEI(4 cycles)
let acc: Ext<C::F, C::EF> = builder.eval(zero + zero);

for (i, va) in a.iter().enumerate() {
let vb = builder.get(b, i);
builder.assign(&acc, acc + *va * vb);
}

acc
}

pub fn reverse<C: Config, T: MemVariable<C>>(
builder: &mut Builder<C>,
arr: &Array<C, T>,
Expand Down
21 changes: 10 additions & 11 deletions src/tower_verifier/program.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,8 +2,7 @@ use super::binding::{
IOPProverMessageVariable, PointAndEvalVariable, PointVariable, TowerVerifierInputVariable,
};
use crate::arithmetics::{
challenger_multi_observe, dot_product, dot_product_pt_n_eval, eq_eval, evaluate_at_point,
exts_to_felts, gen_alpha_pows, is_smaller_than, join, product, reverse,
challenger_multi_observe, dot_product, dot_product_pt_n_eval, eq_eval, evaluate_at_point, exts_to_felts, fixed_dot_product, gen_alpha_pows, is_smaller_than, join, product, reverse
};
use crate::transcript::transcript_observe_label;
use openvm_native_compiler::prelude::*;
Expand Down Expand Up @@ -435,18 +434,20 @@ pub fn verify_tower_proof<C: Config>(
// rt' = r_merge || rt
// r_merge.len() == ceil_log2(num_product_fanin)
transcript_observe_label(builder, challenger, b"merge");
let one: Ext<<C as Config>::F, <C as Config>::EF> = builder.constant(C::EF::ONE);
let zero: Ext<<C as Config>::F, <C as Config>::EF> = builder.constant(C::EF::ZERO);

builder.cycle_tracker_start("derive rt_prime");
let r_merge = challenger.sample_ext(builder);

let coeffs: Array<C, Ext<C::F, C::EF>> = builder.dyn_array(num_fanin);
let one: Ext<<C as Config>::F, <C as Config>::EF> = builder.constant(C::EF::ONE);
let c1: Ext<<C as Config>::F, <C as Config>::EF> = builder.eval(one - r_merge.clone());
let c2: Ext<<C as Config>::F, <C as Config>::EF> = builder.eval(r_merge.clone());
builder.set(&coeffs, 0, c1);
builder.set(&coeffs, 1, c2);
let coeffs = vec![c1, c2];

let r_merge_arr = builder.dyn_array(RVar::from(1));
builder.set(&r_merge_arr, 0, r_merge);
let rt_prime = join(builder, &sub_rt, &r_merge_arr);
builder.cycle_tracker_end("derive rt_prime");

// generate next round challenge
let next_alpha_len: Usize<C::N> = builder
Expand All @@ -472,7 +473,7 @@ pub fn verify_tower_proof<C: Config>(
let prod_slice =
builder.get(&tower_verifier_input.prod_specs_eval, spec_index);
let prod_round_slice = builder.get(&prod_slice, round_var);
let evals = dot_product(builder, &prod_round_slice, &coeffs);
let evals = fixed_dot_product(builder, &coeffs, &prod_round_slice, zero);

builder.set(
&prod_spec_point_n_eval,
Expand Down Expand Up @@ -532,15 +533,13 @@ pub fn verify_tower_proof<C: Config>(
let p2 = builder.get(&prod_round_slice, 1);
let q1 = builder.get(&prod_round_slice, 2);
let q2 = builder.get(&prod_round_slice, 3);
let c1 = builder.get(&coeffs, 0);
let c2 = builder.get(&coeffs, 1);

let p_eval: Ext<<C as Config>::F, <C as Config>::EF> =
builder.constant(C::EF::ZERO);
let q_eval: Ext<<C as Config>::F, <C as Config>::EF> =
builder.constant(C::EF::ZERO);
builder.assign(&p_eval, p1 * c1 + p2 * c2);
builder.assign(&q_eval, q1 * c1 + q2 * c2);
builder.assign(&p_eval, p1 * coeffs[0] + p2 * coeffs[1]);
builder.assign(&q_eval, q1 * coeffs[0] + q2 * coeffs[1]);

builder.set(
&logup_spec_p_point_n_eval,
Expand Down