From 34c7c09ca4fc01d4940ed284d2ce9ba18cb3badc Mon Sep 17 00:00:00 2001
From: fredrikr79 <fredrikrobertsen7@gmail.com>
Date: Mon, 22 Sep 2025 17:20:04 +0200
Subject: [PATCH] ex3: task 3

---
 exercise3/wave_1d_parallel.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/exercise3/wave_1d_parallel.c b/exercise3/wave_1d_parallel.c
index ef9847c..5feac2f 100644
--- a/exercise3/wave_1d_parallel.c
+++ b/exercise3/wave_1d_parallel.c
@@ -19,7 +19,11 @@ typedef double real_t;
 // TASK: T1b
 // Declare variables each MPI process will need
 // BEGIN: T1b
-;
+int comm_size;
+int comm_rank;
+int_t n;
+
+#define I(i) ((i) + n * comm_rank)
 // END: T1b
 
 // Simulation parameters: size, step count, and how often to save the state.
@@ -64,12 +68,13 @@ void domain_save(int_t step) {
 // and set the time step.
 void domain_initialize(void) {
   // BEGIN: T3
-  buffers[0] = malloc((N + 2) * sizeof(real_t));
-  buffers[1] = malloc((N + 2) * sizeof(real_t));
-  buffers[2] = malloc((N + 2) * sizeof(real_t));
+  const int_t bufsize = (comm_rank == ROOT ? N : n + 2);
+  buffers[0] = malloc(bufsize * sizeof(real_t));
+  buffers[1] = malloc(bufsize * sizeof(real_t));
+  buffers[2] = malloc(bufsize * sizeof(real_t));
 
-  for (int_t i = 0; i < N; i++) {
-    U_prv(i) = U(i) = cos(2 * M_PI * i / (real_t)N);
+  for (int_t i = 0; i < n; i++) {
+    U_prv(i) = U(i) = cos(2 * M_PI * (i + offset) / (real_t)N);
   }
   // END: T3