From: Martin Kronbichler <martin.kronbichler@uni-a.de>
Date: Mon, 11 Jul 2022 11:35:14 +0000 (+0200)
Subject: Ensure to look at square of tolerances
X-Git-Tag: v9.5.0-rc1~1088^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F14126%2Fhead;p=dealii.git

Ensure to look at square of tolerances
---

diff --git a/source/fe/mapping_cartesian.cc b/source/fe/mapping_cartesian.cc
index 1620af218e..b08f0d73a2 100644
--- a/source/fe/mapping_cartesian.cc
+++ b/source/fe/mapping_cartesian.cc
@@ -55,8 +55,11 @@ is_cartesian(const CellType &cell)
   if (!cell->reference_cell().is_hyper_cube())
     return false;
 
-  const double abs_tol           = 1e-15;
-  const double rel_tol           = 1e-14;
+  // The tolerances here are somewhat larger than the square of the machine
+  // epsilon, because we are going to compare the square of distances (to
+  // avoid computing square roots).
+  const double abs_tol           = 1e-30;
+  const double rel_tol           = 1e-28;
   const auto   bounding_box      = cell->bounding_box();
   const auto & bounding_vertices = bounding_box.get_boundary_points();
   const auto   bb_diagonal_length_squared =