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Combine eq step constraints into single constraint
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andrewmilson committed Aug 21, 2024
1 parent e0f1063 commit 0d04479
Showing 1 changed file with 13 additions and 4 deletions.
17 changes: 13 additions & 4 deletions crates/prover/src/examples/xor/gkr_lookups/mle_eval.rs
Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,10 @@ impl<const N_VARIABLES: usize> MleEvalPoint<N_VARIABLES> {
_p: p,
}
}

pub fn n_variables(&self) -> usize {
self._p.len()
}
}

/// Evaluates EqEvals constraints on a column.
Expand Down Expand Up @@ -83,18 +87,23 @@ fn eval_eq_constraints<E: EvalAtRow, const N_VARIABLES: usize>(
eval.add_constraint(half_coset0_initial_check + half_coset1_final_check);

// Check all variables except the last (last variable is handled by the constraint above).
#[allow(clippy::needless_range_loop)]
for variable_i in 0..N_VARIABLES.saturating_sub(1) {
let step_constraints = (0..N_VARIABLES.saturating_sub(1)).map(|variable_i| {
let half_coset0_next = next_next;
let half_coset1_prev = next_next;
let [half_coset0_step, half_coset1_step] =
eval.next_interaction_mask(selector_interaction, [0, -1]);
let carry_quotient = mle_eval_point.eq_carry_quotients[variable_i];
// Safe to combine these constraints as `is_step.half_coset0` and `is_step.half_coset1`
// Safe to combine these constraints as `half_coset0_step` and `half_coset1_step`
// are never non-zero at the same time on the trace.
let half_coset0_check = (curr - half_coset0_next * carry_quotient) * half_coset0_step;
let half_coset1_check = (curr * carry_quotient - half_coset1_prev) * half_coset1_step;
eval.add_constraint(half_coset0_check + half_coset1_check);
half_coset0_check + half_coset1_check
});

// Safe to combine into a single constraint as the step selectors are never non-zero on the
// trace at the same time.
if let Some(steps_constraint) = step_constraints.reduce(|a, b| a + b) {
eval.add_constraint(steps_constraint)
}

curr
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