From 0ac8965a3f6bb35b2f59fc93e39505925a51dfc2 Mon Sep 17 00:00:00 2001
From: Jorgen Schartum Dokken <dokken@simula.no>
Date: Tue, 7 Jul 2026 14:11:38 +0200
Subject: [PATCH 1/2] Resolve #324

---
 chapter1/complex_mode.ipynb      | 3 ++-
 chapter1/complex_mode.py         | 3 ++-
 chapter1/fundamentals_code.ipynb | 1 +
 chapter1/fundamentals_code.py    | 1 +
 4 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/chapter1/complex_mode.ipynb b/chapter1/complex_mode.ipynb
index 0fb38eed..78a6efbb 100644
--- a/chapter1/complex_mode.ipynb
+++ b/chapter1/complex_mode.ipynb
@@ -249,7 +249,8 @@
     "local_error = dolfinx.fem.assemble_scalar(L2_error)\n",
     "global_error = np.sqrt(mesh.comm.allreduce(local_error, op=MPI.SUM))\n",
     "max_error = mesh.comm.allreduce(np.max(np.abs(u_c.x.array - uh.x.array)))\n",
-    "print(global_error, max_error)"
+    "if mesh.comm.rank == 0:\n",
+    "    print(f\"{global_error=:.2e}, {max_error=:.2e}\", flush=True)"
    ]
   },
   {
diff --git a/chapter1/complex_mode.py b/chapter1/complex_mode.py
index 6349163a..27a80ed6 100644
--- a/chapter1/complex_mode.py
+++ b/chapter1/complex_mode.py
@@ -172,7 +172,8 @@
 local_error = dolfinx.fem.assemble_scalar(L2_error)
 global_error = np.sqrt(mesh.comm.allreduce(local_error, op=MPI.SUM))
 max_error = mesh.comm.allreduce(np.max(np.abs(u_c.x.array - uh.x.array)))
-print(global_error, max_error)
+if mesh.comm.rank == 0:
+    print(f"{global_error=:.2e}, {max_error=:.2e}", flush=True)
 
 # ## Plotting
 #
diff --git a/chapter1/fundamentals_code.ipynb b/chapter1/fundamentals_code.ipynb
index a8e7a586..75bb9405 100644
--- a/chapter1/fundamentals_code.ipynb
+++ b/chapter1/fundamentals_code.ipynb
@@ -459,6 +459,7 @@
    "outputs": [],
    "source": [
     "error_max = numpy.max(numpy.abs(uD.x.array - uh.x.array))\n",
+    "vertex_max = domain.comm.allreduce(error_max, op=MPI.MAX)\n",
     "if domain.comm.rank == 0:  # Only print the error on one process\n",
     "    print(f\"Error_L2 : {error_L2:.2e}\")\n",
     "    print(f\"Error_max : {error_max:.2e}\")"
diff --git a/chapter1/fundamentals_code.py b/chapter1/fundamentals_code.py
index 2e8b57aa..b63db43e 100644
--- a/chapter1/fundamentals_code.py
+++ b/chapter1/fundamentals_code.py
@@ -301,6 +301,7 @@
 # we can compare the maximum values at any degree of freedom of the approximation space.
 
 error_max = numpy.max(numpy.abs(uD.x.array - uh.x.array))
+vertex_max = domain.comm.allreduce(error_max, op=MPI.MAX)
 if domain.comm.rank == 0:  # Only print the error on one process
     print(f"Error_L2 : {error_L2:.2e}")
     print(f"Error_max : {error_max:.2e}")

From d6dab178866573eee81fd667013b102e52187870 Mon Sep 17 00:00:00 2001
From: Jorgen Schartum Dokken <dokken@simula.no>
Date: Tue, 7 Jul 2026 14:11:50 +0200
Subject: [PATCH 2/2] Further fix

---
 chapter1/fundamentals_code.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/chapter1/fundamentals_code.py b/chapter1/fundamentals_code.py
index b63db43e..4775bb47 100644
--- a/chapter1/fundamentals_code.py
+++ b/chapter1/fundamentals_code.py
@@ -304,7 +304,7 @@
 vertex_max = domain.comm.allreduce(error_max, op=MPI.MAX)
 if domain.comm.rank == 0:  # Only print the error on one process
     print(f"Error_L2 : {error_L2:.2e}")
-    print(f"Error_max : {error_max:.2e}")
+    print(f"Error_max : {vertex_max:.2e}")
 
 # ## Plotting the mesh using pyvista
 # We will visualizing the mesh using [pyvista](https://docs.pyvista.org/), an interface to the VTK toolkit.