From 3fb7ee22240f159fe112240ef0b165a5d0f40eda Mon Sep 17 00:00:00 2001
From: Jean-Paul Pelteret <jppelteret@gmail.com>
Date: Sat, 23 Apr 2022 22:18:51 +0200
Subject: [PATCH] Make vectorization FPE tests more closely match
 implementation that fails, and use values from debug logs.

---
 cmake/checks/check_02_compiler_features.cmake | 59 +++++++++++++++++--
 1 file changed, 54 insertions(+), 5 deletions(-)

diff --git a/cmake/checks/check_02_compiler_features.cmake b/cmake/checks/check_02_compiler_features.cmake
index 4dec8040..761e57a9 100644
--- a/cmake/checks/check_02_compiler_features.cmake
+++ b/cmake/checks/check_02_compiler_features.cmake
@@ -14,10 +14,25 @@
 ## ---------------------------------------------------------------------
 
 
+# Save the current flags
+SET(CMAKE_REQUIRED_LIBRARIES_SAVED ${CMAKE_REQUIRED_LIBRARIES})
+SET(CMAKE_REQUIRED_INCLUDES_SAVED  ${CMAKE_REQUIRED_INCLUDES})
+SET(CMAKE_REQUIRED_FLAGS_SAVED     ${CMAKE_REQUIRED_FLAGS})
+
+# Add deal.II's flags to the current project's
+# (which should be empty unless the user specifies otherwise)
 LIST(APPEND CMAKE_REQUIRED_LIBRARIES ${DEAL_II_LIBRARIES})
 LIST(APPEND CMAKE_REQUIRED_INCLUDES  ${DEAL_II_INCLUDE_DIRS})
 LIST(APPEND CMAKE_REQUIRED_FLAGS     ${DEAL_II_CXX_FLAGS})
 
+IF("${CMAKE_BUILD_TYPE}" STREQUAL "Release")
+  LIST(APPEND CMAKE_REQUIRED_FLAGS   ${DEAL_II_CXX_FLAGS_RELEASE})
+ELSEIF("${CMAKE_BUILD_TYPE}" STREQUAL "Debug")
+  LIST(APPEND CMAKE_REQUIRED_FLAGS   ${DEAL_II_CXX_FLAGS_DEBUG})
+ELSE()
+  MESSAGE(FATAL_ERROR "CMAKE_BUILD_TYPE doesn't match either Release or Debug!")
+ENDIF()
+
 #
 # Check whether division by zero in a vectorized array results in
 # a floating point exception.
@@ -29,16 +44,27 @@ WF_CHECK_CXX_SOURCE_RUNS(
   "
   #include <deal.II/base/vectorization.h>
   using namespace dealii;
+  class BinaryOp
+  {
+  public:
+    template <typename T>
+    T
+    operator()(const T &num, const T &den) const
+    {
+      return num/den;
+    }
+  };
   template <typename Number, std::size_t width>
   void
   do_test()
   {
     using Vec_t = VectorizedArray<Number, width>;
-    for (unsigned int i=0; i<10000; ++i)
+    for (unsigned int i=0; i<100000; ++i)
     {
       const Vec_t num = 1.0;
       const Vec_t den = 0.0;
-      const auto result = num / den;
+      auto result = num / den;
+      result = BinaryOp()(num, den);
       (void)result;
     }
   }
@@ -73,25 +99,42 @@ WF_CHECK_CXX_SOURCE_RUNS(
 # results in a floating point exception.
 #
 # The test is multiple times to ensure that the failure is not in
-# any way sporadic.
+# any way sporadic. The tested value 6.916...e-310 comes from some
+# backtraced output of a test failure on a Docker image. 
 #
 WF_CHECK_CXX_SOURCE_RUNS(
   "
   #include <deal.II/base/vectorization.h>
   #include <limits>
   using namespace dealii;
+  class UnaryOp
+  {
+  public:
+    template <typename T>
+    T
+    operator()(const T &value) const
+    {
+      using namespace std;
+      return sqrt(value);
+    }
+  };
   template <typename Number, std::size_t width>
   void
   do_test()
   {
     using namespace std;
     using Vec_t = VectorizedArray<Number, width>;
-    for (unsigned int i=0; i<10000; ++i)
+    for (unsigned int i=0; i<100000; ++i)
     {
       Vec_t val = 0.0;
       auto result = sqrt(val);
+      result = UnaryOp()(val);
       val = std::numeric_limits<Number>::epsilon();
       result = sqrt(val);
+      result = UnaryOp()(val);
+      val = 6.9161116785120245e-310;
+      result = sqrt(val);
+      result = UnaryOp()(val);
       (void)result;
     }
   }
@@ -118,4 +161,10 @@ WF_CHECK_CXX_SOURCE_RUNS(
     return 0;
   }
   "
-  WEAK_FORMS_VECTORIZATION_FPE_SQRT_OF_ZERO)
\ No newline at end of file
+  WEAK_FORMS_VECTORIZATION_FPE_SQRT_OF_ZERO)
+
+
+# Restore all flags
+SET(CMAKE_REQUIRED_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES_SAVED})
+SET(CMAKE_REQUIRED_INCLUDES  ${CMAKE_REQUIRED_INCLUDES_SAVED})
+SET(CMAKE_REQUIRED_FLAGS     ${CMAKE_REQUIRED_FLAGS_SAVED})