From 43e3dc7a9ee58e556eafa845bfe5645cafcd0f8d Mon Sep 17 00:00:00 2001
From: Axel Kohlmeyer <akohlmey@gmail.com>
Date: Sat, 22 Oct 2022 08:10:00 -0400
Subject: [PATCH] use inline insertion sort for short array

---
 src/REACTION/fix_bond_react.cpp | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/REACTION/fix_bond_react.cpp b/src/REACTION/fix_bond_react.cpp
index bf931fadd1..87573040f7 100644
--- a/src/REACTION/fix_bond_react.cpp
+++ b/src/REACTION/fix_bond_react.cpp
@@ -1735,7 +1735,16 @@ void FixBondReact::inner_crosscheck_loop()
   // ...actually, avail_guesses should never be zero here anyway
   if (guess_branch[avail_guesses-1] == 0) guess_branch[avail_guesses-1] = num_choices;
 
-  std::sort(tag_choices, tag_choices + num_choices);
+  for (int i=1; i < num_choices; ++i) {
+    tagint hold = tag_choices[i];
+    int j = i - 1;
+    while ((j >=0) && (tag_choices[j] > hold)) {
+      tag_choices[j+1] = tag_choices[j];
+      --j;
+    }
+    tag_choices[j+1] = hold;
+  }
+
   for (int i = guess_branch[avail_guesses-1]-1; i >= 0; i--) {
     int already_assigned = 0;
     for (int j = 0; j < onemol->natoms; j++) {