From 4efc5064b7dfe510f6529f23bf477a3d8c11678a Mon Sep 17 00:00:00 2001
From: jorgensd <dokken92@gmail.com>
Date: Sat, 9 Aug 2025 10:46:10 +0200
Subject: [PATCH] Resolve
 https://github.com/jorgensd/dolfinx-tutorial/issues/117

---
 chapter2/hyperelasticity.ipynb | 12 +++++++++---
 chapter2/hyperelasticity.py    | 12 +++++++++---
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/chapter2/hyperelasticity.ipynb b/chapter2/hyperelasticity.ipynb
index 8666c49f..c1a5b1da 100644
--- a/chapter2/hyperelasticity.ipynb
+++ b/chapter2/hyperelasticity.ipynb
@@ -323,7 +323,7 @@
    "id": "28",
    "metadata": {},
    "source": [
-    "Define form F (we want to find u such that F(u) = 0)"
+    "Define the residual of the equation (we want to find u such that residual(u) = 0)"
    ]
   },
   {
@@ -333,7 +333,9 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "F = ufl.inner(ufl.grad(v), P) * dx - ufl.inner(v, B) * dx - ufl.inner(v, T) * ds(2)"
+    "residual = (\n",
+    "    ufl.inner(ufl.grad(v), P) * dx - ufl.inner(v, B) * dx - ufl.inner(v, T) * ds(2)\n",
+    ")"
    ]
   },
   {
@@ -364,7 +366,11 @@
     "    \"pc_factor_mat_solver_type\": \"mumps\",\n",
     "}\n",
     "problem = NonlinearProblem(\n",
-    "    F, u, bcs=bcs, petsc_options=petsc_options, petsc_options_prefix=\"hyperelasticity\"\n",
+    "    residual,\n",
+    "    u,\n",
+    "    bcs=bcs,\n",
+    "    petsc_options=petsc_options,\n",
+    "    petsc_options_prefix=\"hyperelasticity\",\n",
     ")"
    ]
   },
diff --git a/chapter2/hyperelasticity.py b/chapter2/hyperelasticity.py
index 18839310..14394cd2 100644
--- a/chapter2/hyperelasticity.py
+++ b/chapter2/hyperelasticity.py
@@ -143,9 +143,11 @@ def right(x):
 ds = ufl.Measure("ds", domain=domain, subdomain_data=facet_tag, metadata=metadata)
 dx = ufl.Measure("dx", domain=domain, metadata=metadata)
 
-# Define form F (we want to find u such that F(u) = 0)
+# Define the residual of the equation (we want to find u such that residual(u) = 0)
 
-F = ufl.inner(ufl.grad(v), P) * dx - ufl.inner(v, B) * dx - ufl.inner(v, T) * ds(2)
+residual = (
+    ufl.inner(ufl.grad(v), P) * dx - ufl.inner(v, B) * dx - ufl.inner(v, T) * ds(2)
+)
 
 # As the varitional form is non-linear and written on residual form,
 # we use the non-linear problem class from DOLFINx to set up required structures to use a Newton solver.
@@ -162,7 +164,11 @@ def right(x):
     "pc_factor_mat_solver_type": "mumps",
 }
 problem = NonlinearProblem(
-    F, u, bcs=bcs, petsc_options=petsc_options, petsc_options_prefix="hyperelasticity"
+    residual,
+    u,
+    bcs=bcs,
+    petsc_options=petsc_options,
+    petsc_options_prefix="hyperelasticity",
 )
 
 # We create a function to plot the solution at each time step.