From ac20d1ab41d63096f60cdeac54d1f76cb60b5dff Mon Sep 17 00:00:00 2001
From: Steve Plimpton <sjplimp@sandia.gov>
Date: Mon, 18 Mar 2019 09:52:16 -0600
Subject: [PATCH] fix corner-case issue with hyper communication, also timer

---
 src/REPLICA/fix_hyper_local.cpp | 12 ++++++++++--
 src/REPLICA/hyper.cpp           | 11 ++++++++---
 src/comm_brick.cpp              | 18 ++++++++----------
 3 files changed, 26 insertions(+), 15 deletions(-)

diff --git a/src/REPLICA/fix_hyper_local.cpp b/src/REPLICA/fix_hyper_local.cpp
index 21ad2cd86a..be4a642ebb 100644
--- a/src/REPLICA/fix_hyper_local.cpp
+++ b/src/REPLICA/fix_hyper_local.cpp
@@ -1261,16 +1261,24 @@ void FixHyperLocal::unpack_reverse_comm(int n, int *list, double *buf)
 {
   int i,j,k,m;
 
-  m = 0;
+  // return if n = 0
+  // b/c if there are no atoms (n = 0), the message will not have
+  //   been sent by Comm::reverse_comm_fix() or reverse_comm_fix_variable()
+  // so must not read nonzero from first buf location (would be zero anyway)
+
+  if (n == 0) return;
 
   // STRAIN
   // unpack maxstrain vector
   // nonzero # of entries, each has offset to which atom in receiver's list
   // use MAX, b/c want maximum abs value strain for each atom's bonds
-  
+
+  m = 0;
+
   if (commflag == STRAIN) {
     int offset;
     int nonzero = (int) ubuf(buf[m++]).i;   // # of atoms with values
+
     for (int iatom = 0; iatom < nonzero; iatom++) {
       offset = (int) ubuf(buf[m++]).i;      // offset into list for which atom
       j = list[offset];
diff --git a/src/REPLICA/hyper.cpp b/src/REPLICA/hyper.cpp
index 0d8de6d060..5d820b2e27 100644
--- a/src/REPLICA/hyper.cpp
+++ b/src/REPLICA/hyper.cpp
@@ -181,9 +181,6 @@ void Hyper::command(int narg, char **arg)
 
   if (hyperenable) fix_hyper->init_hyper();
 
-  timer->barrier_start();
-  time_start = timer->get_wall(Timer::TOTAL);
-
   // perform initial minimization and bond list creation
 
   int nevent = 0;
@@ -198,6 +195,14 @@ void Hyper::command(int narg, char **arg)
   if (hyperenable) fix_hyper->build_bond_list(0);
   fix_event->restore_state_quench();
 
+  // reset stats and timers to skip HD setup
+
+  nbuild = ndanger = 0;
+  time_dynamics = time_quench = 0.0;
+
+  timer->barrier_start();
+  time_start = timer->get_wall(Timer::TOTAL);
+
   // main loop: dynamics, store state, quench, check event, restore state
 
   int ecount;
diff --git a/src/comm_brick.cpp b/src/comm_brick.cpp
index 64b21e41c9..330551aaed 100644
--- a/src/comm_brick.cpp
+++ b/src/comm_brick.cpp
@@ -1046,10 +1046,6 @@ void CommBrick::reverse_comm_fix(Fix *fix, int size)
    reverse communication invoked by a Fix with variable size data
    query fix for pack size to insure buf_send is big enough
    handshake sizes before each Irecv/Send to insure buf_recv is big enough
-   this removes the if tests on sendnum and recvnum to make MPI calls,
-     as in reverse_comm_fix(), b/c the caller may still want to
-     exchange a message even if the send/recv swap has no atoms,
-     e.g. a reduced count = 0 of atoms to send/recv, as in fix hyper/local
 ------------------------------------------------------------------------- */
 
 void CommBrick::reverse_comm_fix_variable(Fix *fix)
@@ -1074,12 +1070,14 @@ void CommBrick::reverse_comm_fix_variable(Fix *fix)
                    &nrecv,1,MPI_INT,sendproc[iswap],0,world,
                    MPI_STATUS_IGNORE);
 
-      if (nrecv > maxrecv) grow_recv(nrecv);
-      MPI_Irecv(buf_recv,maxrecv,MPI_DOUBLE,sendproc[iswap],0,
-                world,&request);
-
-      MPI_Send(buf_send,nsend,MPI_DOUBLE,recvproc[iswap],0,world);
-      MPI_Wait(&request,MPI_STATUS_IGNORE);
+      if (sendnum[iswap]) {
+        if (nrecv > maxrecv) grow_recv(nrecv);
+        MPI_Irecv(buf_recv,maxrecv,MPI_DOUBLE,sendproc[iswap],0,
+                  world,&request);
+      }
+      if (recvnum[iswap])
+        MPI_Send(buf_send,nsend,MPI_DOUBLE,recvproc[iswap],0,world);
+      if (sendnum[iswap]) MPI_Wait(&request,MPI_STATUS_IGNORE);
       buf = buf_recv;
     } else buf = buf_send;