diff --git a/src/algorithm/invert.rs b/src/algorithm/invert.rs
index 124f3f7b..fd7fe5f2 100644
--- a/src/algorithm/invert.rs
+++ b/src/algorithm/invert.rs
@@ -1359,7 +1359,7 @@ fn invert_temp_pattern<'a>(
     if let Some((input, start_instr @ Instr::CopyToTemp { span, .. }, inner, end_instr, count)) =
         try_copy_temp_wrap(input)
     {
-        // Pseudo-inverse
+        // On-inverse
         for mid in 0..inner.len() {
             let (before, after) = inner.split_at(mid);
             let Ok(before_sig) = instrs_signature(before) else {
diff --git a/src/algorithm/monadic.rs b/src/algorithm/monadic.rs
index 17cb607c..5a7cb39f 100644
--- a/src/algorithm/monadic.rs
+++ b/src/algorithm/monadic.rs
@@ -778,27 +778,29 @@ impl<T: ArrayValue> Array<T> {
             return;
         }
         let chunk_len: usize = self.shape[depth..].iter().product();
-        if chunk_len == 0 {
+        let subrow_len: usize = self.shape[depth + 1..].iter().product();
+        if chunk_len == 0 || subrow_len == 0 {
             return;
         }
         let is_list = self.rank() == depth + 1;
         let mut new_chunk = Vec::with_capacity(chunk_len);
+        let mut indices = Vec::with_capacity(chunk_len / subrow_len);
         for chunk in self.data.as_mut_slice().chunks_exact_mut(chunk_len) {
             if is_list {
                 chunk.par_sort_by(T::array_cmp);
             } else {
-                let mut indices: Vec<usize> = (0..chunk.len() / chunk_len).collect();
+                indices.extend(0..chunk.len() / subrow_len);
                 indices.par_sort_by(|&a, &b| {
-                    chunk[a * chunk_len..(a + 1) * chunk_len]
+                    chunk[a * subrow_len..(a + 1) * subrow_len]
                         .iter()
-                        .zip(&chunk[b * chunk_len..(b + 1) * chunk_len])
+                        .zip(&chunk[b * subrow_len..(b + 1) * subrow_len])
                         .map(|(a, b)| a.array_cmp(b))
                         .find(|x| x != &Ordering::Equal)
                         .unwrap_or(Ordering::Equal)
                 });
                 new_chunk.clear();
-                for i in indices {
-                    new_chunk.extend_from_slice(&chunk[i * chunk_len..(i + 1) * chunk_len]);
+                for i in indices.drain(..) {
+                    new_chunk.extend_from_slice(&chunk[i * subrow_len..(i + 1) * subrow_len]);
                 }
                 chunk.clone_from_slice(&new_chunk);
             }
@@ -810,27 +812,29 @@ impl<T: ArrayValue> Array<T> {
             return;
         }
         let chunk_len: usize = self.shape[depth..].iter().product();
-        if chunk_len == 0 {
+        let subrow_len: usize = self.shape[depth + 1..].iter().product();
+        if chunk_len == 0 || subrow_len == 0 {
             return;
         }
         let is_list = self.rank() == depth + 1;
         let mut new_chunk = Vec::with_capacity(chunk_len);
+        let mut indices = Vec::with_capacity(chunk_len / subrow_len);
         for chunk in self.data.as_mut_slice().chunks_exact_mut(chunk_len) {
             if is_list {
                 chunk.par_sort_by(|a, b| b.array_cmp(a));
             } else {
-                let mut indices: Vec<usize> = (0..chunk.len() / chunk_len).collect();
+                indices.extend(0..chunk.len() / subrow_len);
                 indices.par_sort_by(|&a, &b| {
-                    chunk[a * chunk_len..(a + 1) * chunk_len]
+                    chunk[a * subrow_len..(a + 1) * subrow_len]
                         .iter()
-                        .zip(&chunk[b * chunk_len..(b + 1) * chunk_len])
+                        .zip(&chunk[b * subrow_len..(b + 1) * subrow_len])
                         .map(|(a, b)| b.array_cmp(a))
                         .find(|x| x != &Ordering::Equal)
                         .unwrap_or(Ordering::Equal)
                 });
                 new_chunk.clear();
-                for i in indices {
-                    new_chunk.extend_from_slice(&chunk[i * chunk_len..(i + 1) * chunk_len]);
+                for i in indices.drain(..) {
+                    new_chunk.extend_from_slice(&chunk[i * subrow_len..(i + 1) * subrow_len]);
                 }
                 chunk.clone_from_slice(&new_chunk);
             }
diff --git a/tests/optimized.ua b/tests/optimized.ua
index 076a5289..1986d20e 100644
--- a/tests/optimized.ua
+++ b/tests/optimized.ua
@@ -31,8 +31,11 @@
 ⍤⟜≍: ⟜(≡⊂≡°⊂)↯3_3_3⇡27
 ⍤⟜≍: ⟜(≡≡⊂≡≡°⊂)↯3_3_3⇡27
 
-# Rows sort
+# Sort
+⍤⟜≍: ⇌ ⟜(⊏⍏.) ↯3_3⇌⇡9
+⍤⟜≍: ⇌ ⟜(⊏⍖.) ↯3_3⇌9
 ⍤⟜≍: ⇌↯3_3⇡9 ≡(⊏⍏.) ↯3_3⇌⇡9
+⍤⟜≍: ≡⇌ ⟜≡(⊏⍖.) ↯3_3⇡9
 
 # Adjacent
 ⍤⟜≍: [3 5 7] ≡/+◫2 [1 2 3 4]