From 136901c5ad86426d1a19efd6b8d79eaaa63d6fa4 Mon Sep 17 00:00:00 2001
From: Fabio Luporini <f.luporini12@imperial.ac.uk>
Date: Tue, 5 Oct 2021 10:22:52 +0200
Subject: [PATCH] mpi: Patch neighborhood construction

---
 devito/mpi/distributed.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/devito/mpi/distributed.py b/devito/mpi/distributed.py
index e5e1475fbc..5d488d35b7 100644
--- a/devito/mpi/distributed.py
+++ b/devito/mpi/distributed.py
@@ -367,11 +367,11 @@ def neighborhood(self):
         # Set up diagonal neighbours
         for i in product([LEFT, CENTER, RIGHT], repeat=self.ndim):
             neighbor = [c + s.val for c, s in zip(self.mycoords, i)]
-            try:
-                ret[i] = self.comm.Get_cart_rank(neighbor)
-            except:
-                # Fallback for MPI ranks at the grid boundary
+
+            if any(c < 0 or c >= s for c, s in zip(neighbor, self.topology)):
                 ret[i] = MPI.PROC_NULL
+            else:
+                ret[i] = self.comm.Get_cart_rank(neighbor)
 
         return ret