From 858065029d27622049e64388a642a7d2b986b258 Mon Sep 17 00:00:00 2001
From: David Nicholson <davidanich@gmail.com>
Date: Sun, 12 Nov 2017 15:46:51 -0500
Subject: [PATCH] Reverse communication compute fragment/aggregate

---
 src/compute_aggregate_atom.cpp | 45 +++++++++++++++++++++++++++++++++-
 src/compute_aggregate_atom.h   |  2 ++
 src/compute_fragment_atom.cpp  | 45 +++++++++++++++++++++++++++++++++-
 src/compute_fragment_atom.h    |  2 ++
 4 files changed, 92 insertions(+), 2 deletions(-)

diff --git a/src/compute_aggregate_atom.cpp b/src/compute_aggregate_atom.cpp
index 1155ac437a..f92bf02cba 100644
--- a/src/compute_aggregate_atom.cpp
+++ b/src/compute_aggregate_atom.cpp
@@ -51,6 +51,7 @@ ComputeAggregateAtom::ComputeAggregateAtom(LAMMPS *lmp, int narg, char **arg) :
   peratom_flag = 1;
   size_peratom_cols = 0;
   comm_forward = 1;
+  comm_reverse = 1;
 
   nmax = 0;
 }
@@ -163,6 +164,11 @@ void ComputeAggregateAtom::compute_peratom()
   while (1) {
     comm->forward_comm_compute(this);
 
+    // reverse communication when bonds are not stored on every processor
+
+    if (force->newton_bond)
+      comm->reverse_comm_compute(this);
+
     change = 0;
     while (1) {
       done = 1;
@@ -252,13 +258,50 @@ void ComputeAggregateAtom::unpack_forward_comm(int n, int first, double *buf)
   m = 0;
   last = first + n;
   if (commflag)
-    for (i = first; i < last; i++) aggregateID[i] = buf[m++];
+    for (i = first; i < last; i++) {
+      double x = buf[m++];
+
+      // only overwrite ghost IDs with values lower than current ones
+
+      aggregateID[i] = MIN(x,aggregateID[i]);
+    }
   else {
     int *mask = atom->mask;
     for (i = first; i < last; i++) mask[i] = (int) ubuf(buf[m++]).i;
   }
 }
 
+/* ---------------------------------------------------------------------- */
+
+int ComputeAggregateAtom::pack_reverse_comm(int n, int first, double *buf)
+{
+  int i,m,last;
+
+  m = 0;
+  last = first + n;
+  for (i = first; i < last; i++) {
+    buf[m++] = aggregateID[i];
+  }
+  return m;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void ComputeAggregateAtom::unpack_reverse_comm(int n, int *list, double *buf)
+{
+  int i,j,m;
+
+  m = 0;
+  for (i = 0; i < n; i++) {
+    j = list[i];
+    double x = buf[m++];
+
+    // only overwrite local IDs with values lower than current ones
+
+    aggregateID[j] = MIN(x,aggregateID[j]);
+  }
+}
+
 /* ----------------------------------------------------------------------
    memory usage of local atom-based array
 ------------------------------------------------------------------------- */
diff --git a/src/compute_aggregate_atom.h b/src/compute_aggregate_atom.h
index 8170aabc7f..dc2e1d7b40 100644
--- a/src/compute_aggregate_atom.h
+++ b/src/compute_aggregate_atom.h
@@ -33,6 +33,8 @@ class ComputeAggregateAtom : public Compute {
   void compute_peratom();
   int pack_forward_comm(int, int *, double *, int, int *);
   void unpack_forward_comm(int, int, double *);
+  int pack_reverse_comm(int, int, double *);
+  void unpack_reverse_comm(int, int *, double *);
   double memory_usage();
 
  private:
diff --git a/src/compute_fragment_atom.cpp b/src/compute_fragment_atom.cpp
index 2dfb20a570..8606f54933 100644
--- a/src/compute_fragment_atom.cpp
+++ b/src/compute_fragment_atom.cpp
@@ -44,6 +44,7 @@ ComputeFragmentAtom::ComputeFragmentAtom(LAMMPS *lmp, int narg, char **arg) :
   peratom_flag = 1;
   size_peratom_cols = 0;
   comm_forward = 1;
+  comm_reverse = 1;
 
   nmax = 0;
 }
@@ -122,6 +123,11 @@ void ComputeFragmentAtom::compute_peratom()
   while (1) {
     comm->forward_comm_compute(this);
 
+    // reverse communication when bonds are not stored on every processor
+
+    if (force->newton_bond)
+      comm->reverse_comm_compute(this);
+
     change = 0;
     while (1) {
       done = 1;
@@ -183,13 +189,50 @@ void ComputeFragmentAtom::unpack_forward_comm(int n, int first, double *buf)
   m = 0;
   last = first + n;
   if (commflag)
-    for (i = first; i < last; i++) fragmentID[i] = buf[m++];
+    for (i = first; i < last; i++) {
+      double x = buf[m++];
+
+      // only overwrite ghost IDs with values lower than current ones
+
+      fragmentID[i] = MIN(x,fragmentID[i]);
+    }
   else {
     int *mask = atom->mask;
     for (i = first; i < last; i++) mask[i] = (int) ubuf(buf[m++]).i;
   }
 }
 
+/* ---------------------------------------------------------------------- */
+
+int ComputeFragmentAtom::pack_reverse_comm(int n, int first, double *buf)
+{
+  int i,m,last;
+
+  m = 0;
+  last = first + n;
+  for (i = first; i < last; i++) {
+    buf[m++] = fragmentID[i];
+  }
+  return m;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void ComputeFragmentAtom::unpack_reverse_comm(int n, int *list, double *buf)
+{
+  int i,j,m;
+
+  m = 0;
+  for (i = 0; i < n; i++) {
+    j = list[i];
+    double x = buf[m++];
+
+    // only overwrite local IDs with values lower than current ones
+
+    fragmentID[j] = MIN(x,fragmentID[j]);
+  }
+}
+
 /* ----------------------------------------------------------------------
    memory usage of local atom-based array
 ------------------------------------------------------------------------- */
diff --git a/src/compute_fragment_atom.h b/src/compute_fragment_atom.h
index a56239dbda..2365b6028b 100644
--- a/src/compute_fragment_atom.h
+++ b/src/compute_fragment_atom.h
@@ -32,6 +32,8 @@ class ComputeFragmentAtom : public Compute {
   void compute_peratom();
   int pack_forward_comm(int, int *, double *, int, int *);
   void unpack_forward_comm(int, int, double *);
+  int pack_reverse_comm(int, int, double *);
+  void unpack_reverse_comm(int, int *, double *);
   double memory_usage();
 
  private: