From d35c27167742bd457abc2a36a2fa95ca6b96312f Mon Sep 17 00:00:00 2001
From: Axel Kohlmeyer <akohlmey@gmail.com>
Date: Fri, 27 Oct 2023 19:10:55 -0400
Subject: [PATCH] limit the maximum number of iterations so the LAMMPS
 simulation will not stall

---
 src/compute_cluster_atom.cpp  |  9 +++++++--
 src/compute_fragment_atom.cpp | 10 ++++++++--
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/src/compute_cluster_atom.cpp b/src/compute_cluster_atom.cpp
index ae44fbcd37..0d60b8b993 100644
--- a/src/compute_cluster_atom.cpp
+++ b/src/compute_cluster_atom.cpp
@@ -29,6 +29,7 @@
 
 using namespace LAMMPS_NS;
 
+static constexpr int MAXLOOP = 100;
 /* ---------------------------------------------------------------------- */
 
 ComputeClusterAtom::ComputeClusterAtom(LAMMPS *lmp, int narg, char **arg) :
@@ -136,9 +137,11 @@ void ComputeClusterAtom::compute_peratom()
 
   int change, done, anychange;
 
-  while (true) {
+  int counter = 0;
+  // stop after MAXLOOP iterations
+  while (counter < MAXLOOP) {
     comm->forward_comm(this);
-
+    ++counter;
     change = 0;
     while (true) {
       done = 1;
@@ -177,6 +180,8 @@ void ComputeClusterAtom::compute_peratom()
     MPI_Allreduce(&change, &anychange, 1, MPI_INT, MPI_MAX, world);
     if (!anychange) break;
   }
+  if ((comm->me == 0) && (counter >= MAXLOOP))
+    error->warning(FLERR, "Compute cluster/atom did not converge after {} iterations", MAXLOOP);
 }
 
 /* ---------------------------------------------------------------------- */
diff --git a/src/compute_fragment_atom.cpp b/src/compute_fragment_atom.cpp
index 035f554c8d..7e3f3437b6 100644
--- a/src/compute_fragment_atom.cpp
+++ b/src/compute_fragment_atom.cpp
@@ -31,7 +31,8 @@
 
 using namespace LAMMPS_NS;
 
-#define BIG 1.0e20
+static constexpr double BIG = 1.0e20;
+static constexpr int MAXLOOP = 100;
 
 /* ---------------------------------------------------------------------- */
 
@@ -145,8 +146,11 @@ void ComputeFragmentAtom::compute_peratom()
 
   commflag = 1;
 
-  while (true) {
+  int counter = 0;
+  // stop after MAXLOOP iterations
+  while (counter < MAXLOOP) {
     comm->forward_comm(this);
+    ++counter;
     done = 1;
 
     // set markflag = 0 for all owned atoms, for new iteration
@@ -223,6 +227,8 @@ void ComputeFragmentAtom::compute_peratom()
     MPI_Allreduce(&done,&alldone,1,MPI_INT,MPI_MIN,world);
     if (alldone) break;
   }
+  if ((comm->me == 0) && (counter >= MAXLOOP))
+    error->warning(FLERR, "Compute fragment/atom did not converge after {} iterations", MAXLOOP);
 }
 
 /* ---------------------------------------------------------------------- */