From afaf992ac2cb9e1bc2a92f21278a9a6c7a281aa1 Mon Sep 17 00:00:00 2001
From: jtclemm <jtclemm@sandia.gov>
Date: Fri, 21 May 2021 11:06:34 -0600
Subject: [PATCH] Second working of bits for neigh/history

---
 src/MISC/pair_tracker.cpp |  1 +
 src/fix_neigh_history.cpp | 19 +++++++++++++------
 src/fix_neigh_history.h   |  1 +
 3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/src/MISC/pair_tracker.cpp b/src/MISC/pair_tracker.cpp
index 7a7bb57f21..e3fd64d0d6 100644
--- a/src/MISC/pair_tracker.cpp
+++ b/src/MISC/pair_tracker.cpp
@@ -290,6 +290,7 @@ void PairTracker::init_style()
     int ifix = modify->find_fix("NEIGH_HISTORY_TRACK");
     fix_history = (FixNeighHistory *) modify->fix[ifix];
     fix_history->pair = this;
+    fix_history->use_bit_flag = 0;
   }
 
   if (finitecutflag) {
diff --git a/src/fix_neigh_history.cpp b/src/fix_neigh_history.cpp
index e0c49e7caa..2fad4ad200 100644
--- a/src/fix_neigh_history.cpp
+++ b/src/fix_neigh_history.cpp
@@ -44,6 +44,7 @@ FixNeighHistory::FixNeighHistory(LAMMPS *lmp, int narg, char **arg) :
 
   create_attribute = 1;
   maxexchange_dynamic = 1;
+  use_bit_flag = 1;
 
   newton_pair = force->newton_pair;
 
@@ -623,15 +624,21 @@ void FixNeighHistory::post_neighbor()
 
     for (jj = 0; jj < jnum; jj++) {
       j = jlist[jj];
-      rflag = sbmask(j) | pair->beyond_contact | (!pair->finitecutflag);
-      j &= NEIGHMASK;
-      jlist[jj] = j;
+      
+      if (use_bit_flag) {
+        rflag = sbmask(j) | pair->beyond_contact;
+        j &= NEIGHMASK;    
+        jlist[jj] = j;
+      } else {
+        rflag = 1;
+        j &= NEIGHMASK;      
+      }
 
-      // rflag = 1 if r < radsum in npair_size() method
+      // rflag = 1 if r < radsum in npair_size() method or if pair interactions extend further
       // preserve neigh history info if tag[j] is in old-neigh partner list
       // this test could be more geometrically precise for two sphere/line/tri
-      // for pair styles with interactions not set by finite sizes, always record data since
-      // npair classes do not apply a mask for history (those bits are used for special bonds)
+      // if use_bit_flag is turned off, always record data since not all npair classes 
+      // apply a mask for history (and they could use the bits for special bonds)
 
       if (rflag) {
         jtag = tag[j];
diff --git a/src/fix_neigh_history.h b/src/fix_neigh_history.h
index 57391cfa9a..f6dee02cb5 100644
--- a/src/fix_neigh_history.h
+++ b/src/fix_neigh_history.h
@@ -28,6 +28,7 @@ class FixNeighHistory : public Fix {
  public:
   int nlocal_neigh;             // nlocal at last time neigh list was built
   int nall_neigh;               // ditto for nlocal+nghost
+  int use_bit_flag;             // flag whether fix neigh history uses extra bit in neighborlist
   int **firstflag;              // ptr to each atom's neighbor flsg
   double **firstvalue;          // ptr to each atom's values
   class Pair *pair;             // ptr to pair style that uses neighbor history