From: Rene Gassmoeller <rene.gassmoeller@mailbox.org>
Date: Mon, 10 Jun 2024 17:26:02 +0000 (-0400)
Subject: Fix division by zero that should never happen.
X-Git-Tag: v9.6.0-rc1~179^2~1
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a0d65191fb07ba10b2fd5466a4bf38aacbb7c9e2;p=dealii.git

Fix division by zero that should never happen.
---

diff --git a/source/particles/particle_handler.cc b/source/particles/particle_handler.cc
index 7280ba15e2..c345341e9d 100644
--- a/source/particles/particle_handler.cc
+++ b/source/particles/particle_handler.cc
@@ -1348,7 +1348,12 @@ namespace Particles
               current_cell, out_particle->get_location(), *mapping);
           Tensor<1, spacedim> vertex_to_particle =
             out_particle->get_location() - current_cell->vertex(closest_vertex);
-          vertex_to_particle /= vertex_to_particle.norm();
+
+          // Only normalize if vector is larger than zero, the algorithm below
+          // works fine for zero vectors.
+          if (vertex_to_particle.norm() >
+              100. * std::numeric_limits<double>::epsilon())
+            vertex_to_particle /= vertex_to_particle.norm();
 
           const unsigned int closest_vertex_index =
             current_cell->vertex_index(closest_vertex);