From 165c18a6fe12a0a93a6fd2ad547dbc287cd53c58 Mon Sep 17 00:00:00 2001
From: fredrikr79 <fredrikrobertsen7@gmail.com>
Date: Mon, 22 Sep 2025 19:25:07 +0200
Subject: [PATCH] ex3: task 6

---
 exercise3/wave_1d_parallel.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/exercise3/wave_1d_parallel.c b/exercise3/wave_1d_parallel.c
index ef9847c..fc2ac7c 100644
--- a/exercise3/wave_1d_parallel.c
+++ b/exercise3/wave_1d_parallel.c
@@ -106,8 +106,12 @@ void time_step(void) {
 // Neumann (reflective) boundary condition.
 void boundary_condition(void) {
   // BEGIN: T6
-  U(-1) = U(1);
-  U(N) = U(N - 2);
+  if (comm_rank == ROOT) {
+    U(-1) = U(1);
+  }
+  if (comm_rank == comm_size - 1) {
+    U(n) = U(n - 2);
+  }
   // END: T6
 }