From: Martin Kronbichler <kronbichler@lnm.mw.tum.de>
Date: Mon, 22 Jul 2019 10:34:01 +0000 (+0200)
Subject: Choose a more appropriate tolerance for vector add_and_dot
X-Git-Tag: v9.2.0-rc1~1361^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F8402%2Fhead;p=dealii.git

Choose a more appropriate tolerance for vector add_and_dot
---

diff --git a/tests/lac/la_parallel_vector_add_and_dot_complex.cc b/tests/lac/la_parallel_vector_add_and_dot_complex.cc
index 5b5f21631b..88734d847e 100644
--- a/tests/lac/la_parallel_vector_add_and_dot_complex.cc
+++ b/tests/lac/la_parallel_vector_add_and_dot_complex.cc
@@ -61,14 +61,18 @@ check()
         }
 
       deallog << "Add and dot is ";
-      if (std::abs(prod - prod_check) <
-          4. * std::numeric_limits<number>::epsilon() *
-            std::sqrt(static_cast<number>(size)) * size)
+      // check tolerance with respect to the expected size of result which is
+      // ~ size^2 including the roundoff error ~ sqrt(size) we expect
+      const number tolerance = 4. * std::numeric_limits<number>::epsilon() *
+                               std::sqrt(static_cast<number>(size)) * size *
+                               size;
+      if (std::abs(prod - prod_check) < tolerance)
         deallog << "correct" << std::endl;
       else
-        deallog << "wrong; should be " << prod / static_cast<number>(size)
-                << ", is " << prod_check / static_cast<number>(size)
-                << std::endl;
+        deallog << "wrong by " << std::abs(prod - prod_check)
+                << " with tolerance " << tolerance << "; should be "
+                << prod / static_cast<number>(size) << ", is "
+                << prod_check / static_cast<number>(size) << std::endl;
     }
 }
 
diff --git a/tests/lac/la_vector_add_and_dot_complex.cc b/tests/lac/la_vector_add_and_dot_complex.cc
index f86fd6453e..c4dfbf3a0a 100644
--- a/tests/lac/la_vector_add_and_dot_complex.cc
+++ b/tests/lac/la_vector_add_and_dot_complex.cc
@@ -58,14 +58,18 @@ check()
         }
 
       deallog << "Add and dot is ";
-      if (std::abs(prod - prod_check) <
-          4. * std::numeric_limits<number>::epsilon() *
-            std::sqrt(static_cast<number>(size)) * size)
+      // check tolerance with respect to the expected size of result which is
+      // ~ size^2 including the roundoff error ~ sqrt(size) we expect
+      const number tolerance = 4. * std::numeric_limits<number>::epsilon() *
+                               std::sqrt(static_cast<number>(size)) * size *
+                               size;
+      if (std::abs(prod - prod_check) < tolerance)
         deallog << "correct" << std::endl;
       else
-        deallog << "wrong; should be " << prod / static_cast<number>(size)
-                << ", is " << prod_check / static_cast<number>(size)
-                << std::endl;
+        deallog << "wrong by " << std::abs(prod - prod_check)
+                << " with tolerance " << tolerance << "; should be "
+                << prod / static_cast<number>(size) << ", is "
+                << prod_check / static_cast<number>(size) << std::endl;
     }
 }
 
diff --git a/tests/lac/vector_add_and_dot_complex.cc b/tests/lac/vector_add_and_dot_complex.cc
index 20396444de..48f8fbe585 100644
--- a/tests/lac/vector_add_and_dot_complex.cc
+++ b/tests/lac/vector_add_and_dot_complex.cc
@@ -55,14 +55,18 @@ check()
         }
 
       deallog << "Add and dot is ";
-      if (std::abs(prod - prod_check) <
-          4. * std::abs(std::numeric_limits<number>::epsilon()) *
-            std::sqrt(static_cast<double>(size)) * size)
+      // check tolerance with respect to the expected size of result which is
+      // ~ size^2 including the roundoff error ~ sqrt(size) we expect
+      const number tolerance = 4. * std::numeric_limits<number>::epsilon() *
+                               std::sqrt(static_cast<number>(size)) * size *
+                               size;
+      if (std::abs(prod - prod_check) < tolerance)
         deallog << "correct" << std::endl;
       else
-        deallog << "wrong; should be " << prod / static_cast<number>(size)
-                << ", is " << prod_check / static_cast<number>(size)
-                << std::endl;
+        deallog << "wrong by " << std::abs(prod - prod_check)
+                << " with tolerance " << tolerance << "; should be "
+                << prod / static_cast<number>(size) << ", is "
+                << prod_check / static_cast<number>(size) << std::endl;
     }
 }