From 651ef2304256503393d3a2dec8b772471a421909 Mon Sep 17 00:00:00 2001
From: WickedJack99 <github.0yiic@passmail.net>
Date: Sun, 29 Jun 2025 20:18:09 +0200
Subject: [PATCH] ...

---
 lab12/exc4/jacobi.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lab12/exc4/jacobi.cpp b/lab12/exc4/jacobi.cpp
index 02f8383..12fc5f2 100644
--- a/lab12/exc4/jacobi.cpp
+++ b/lab12/exc4/jacobi.cpp
@@ -159,7 +159,7 @@ void Jacobi::exchangeHaloLayersNodeMPIProcSecond(Matrix &phi)
   // Communication with lower partner
   if (!isFirstRank())
   {
-    int lower = rank_ - 1;
+    int lower = rank_ + 1;
     MPI_Isend(&phi(1, 0), sendSize, MPI_DOUBLE, lower, tag, MPI_COMM_WORLD,
               &req.emplace_back());
     MPI_Irecv(&phi(0, 0), sendSize, MPI_DOUBLE, lower, tag, MPI_COMM_WORLD,