From 4d70f2f8d943f809061f0fcf1d503854c3b2ae89 Mon Sep 17 00:00:00 2001
From: Chris Richardson <chris@bpi.cam.ac.uk>
Date: Fri, 20 Dec 2024 10:53:32 +0000
Subject: [PATCH] Fix for mixed topology when mixing cells with different facet
 types in 3D (#3572)

---
 cpp/dolfinx/fem/dofmapbuilder.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/cpp/dolfinx/fem/dofmapbuilder.cpp b/cpp/dolfinx/fem/dofmapbuilder.cpp
index 676bb48eeba..78bf8a8c5b7 100644
--- a/cpp/dolfinx/fem/dofmapbuilder.cpp
+++ b/cpp/dolfinx/fem/dofmapbuilder.cpp
@@ -279,6 +279,10 @@ build_basic_dofmaps(
 
         const std::vector<std::vector<int>>& e_dofs_d = entity_dofs[d];
 
+        // Skip over undefined topology, e.g. quad facets of tetrahedra
+        if (d < D and !topology.connectivity({D, i}, {d, et}))
+          continue;
+
         // Iterate over each entity of current dimension d and type et
         std::span<const std::int32_t> c_to_e
             = d < D ? topology.connectivity({D, i}, {d, et})->links(c)