From 7e81d48a317e037e551b3f9fc3b82a34fd493442 Mon Sep 17 00:00:00 2001
From: Tom French <15848336+TomAFrench@users.noreply.github.com>
Date: Wed, 21 Jan 2026 13:39:20 +0000
Subject: [PATCH 1/2] feat: unroll loop for adding final fields into state

---
 src/poseidon2.nr | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/src/poseidon2.nr b/src/poseidon2.nr
index 27b9255..97bcbb9 100644
--- a/src/poseidon2.nr
+++ b/src/poseidon2.nr
@@ -70,10 +70,23 @@ impl Poseidon2 {
             }
 
             // handle remaining elements after last full RATE-sized chunk
-            let remainder_start = (in_len / RATE) * RATE;
-            for j in remainder_start..in_len {
-                state[j - remainder_start] += input[j];
-            }
+            let num_extra_fields = in_len % RATE;
+            let remainder_start = in_len - num_extra_fields;
+            state[0] += if num_extra_fields > 0 {
+                input[remainder_start]
+            } else {
+                0
+            };
+            state[1] += if num_extra_fields > 1 {
+                input[remainder_start + 1]
+            } else {
+                0
+            };
+            state[2] += if num_extra_fields > 2 {
+                input[remainder_start + 2]
+            } else {
+                0
+            };
         } else {
             let mut states: [[Field; 4]; N / RATE + 1] = [[0; 4]; N / RATE + 1];
             states[0] = state;

From c92ab8fa07cef647b3a36434404271d3780fe0ba Mon Sep 17 00:00:00 2001
From: Tom French <15848336+TomAFrench@users.noreply.github.com>
Date: Wed, 21 Jan 2026 17:26:33 +0000
Subject: [PATCH 2/2] feat: remove unnecessary state write

---
 src/poseidon2.nr | 23 +++++++----------------
 1 file changed, 7 insertions(+), 16 deletions(-)

diff --git a/src/poseidon2.nr b/src/poseidon2.nr
index 97bcbb9..9183560 100644
--- a/src/poseidon2.nr
+++ b/src/poseidon2.nr
@@ -71,22 +71,13 @@ impl Poseidon2 {
 
             // handle remaining elements after last full RATE-sized chunk
             let num_extra_fields = in_len % RATE;
-            let remainder_start = in_len - num_extra_fields;
-            state[0] += if num_extra_fields > 0 {
-                input[remainder_start]
-            } else {
-                0
-            };
-            state[1] += if num_extra_fields > 1 {
-                input[remainder_start + 1]
-            } else {
-                0
-            };
-            state[2] += if num_extra_fields > 2 {
-                input[remainder_start + 2]
-            } else {
-                0
-            };
+            if num_extra_fields != 0 {
+                let remainder_start = in_len - num_extra_fields;
+                state[0] += input[remainder_start];
+                if num_extra_fields > 1 {
+                    state[1] += input[remainder_start + 1]
+                }
+            }
         } else {
             let mut states: [[Field; 4]; N / RATE + 1] = [[0; 4]; N / RATE + 1];
             states[0] = state;