From 19cbbd4d12667da75047913dda43416bd2a8e20c Mon Sep 17 00:00:00 2001
From: wborgeaud <williamborgeaud@gmail.com>
Date: Fri, 25 Mar 2022 08:01:22 +0100
Subject: [PATCH] Minor

---
 plonky2/src/gates/selectors.rs       | 10 +++++++++-
 plonky2/src/plonk/circuit_builder.rs |  7 ++-----
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/plonky2/src/gates/selectors.rs b/plonky2/src/gates/selectors.rs
index ed251237..a5d15f87 100644
--- a/plonky2/src/gates/selectors.rs
+++ b/plonky2/src/gates/selectors.rs
@@ -20,8 +20,16 @@ pub(crate) struct SelectorsInfo {
 /// Partition the gates into (the smallest amount of) groups `{ G_i }`, such that for each group `G`
 /// `|G| + max_{g in G} g.degree() <= max_degree`. These groups are constructed greedily from
 /// the list of gates sorted by degree.
+/// We build a selector polynomial `S_i` for each group `G_i`, with
+/// ```
+/// S_i[j] =
+///     if j-th row gate=g_k in G_i
+///         k
+///     else
+///         UNUSED_SELECTOR
+/// ```
 pub(crate) fn selector_polynomials<F: RichField + Extendable<D>, const D: usize>(
-    gates: Vec<GateRef<F, D>>,
+    gates: &[GateRef<F, D>],
     instances: &[GateInstance<F, D>],
     max_degree: usize,
 ) -> (Vec<PolynomialValues<F>>, SelectorsInfo) {
diff --git a/plonky2/src/plonk/circuit_builder.rs b/plonky2/src/plonk/circuit_builder.rs
index 7fbc67f4..12180600 100644
--- a/plonky2/src/plonk/circuit_builder.rs
+++ b/plonky2/src/plonk/circuit_builder.rs
@@ -667,11 +667,8 @@ impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
         let quotient_degree_factor = self.config.max_quotient_degree_factor;
         let mut gates = self.gates.iter().cloned().collect::<Vec<_>>();
         gates.sort_unstable_by_key(|g| (g.0.degree(), g.0.id()));
-        let (mut constant_vecs, selectors_info) = selector_polynomials(
-            gates.clone(),
-            &self.gate_instances,
-            quotient_degree_factor + 1,
-        );
+        let (mut constant_vecs, selectors_info) =
+            selector_polynomials(&gates, &self.gate_instances, quotient_degree_factor + 1);
         constant_vecs.extend(self.constant_polys());
         let num_constants = constant_vecs.len();