[base] Fixed AlmostEqualULPs in case of possible int overflow.

Signed-off-by: Viktor Govako <viktor.govako@gmail.com>

base/CMakeLists.txt

@@ -42,6 +42,7 @@ set(
   lower_case.cpp
   lru_cache.hpp
   macros.hpp
+  math.cpp
   math.hpp
   matrix.hpp
   mem_trie.hpp

base/base_tests/math_test.cpp

@@ -46,7 +46,7 @@ UNIT_TEST(PowUInt)
   TEST_EQUAL(base::PowUint(3, 10), 59049, ());
 }
 
-UNIT_TEST(AlmostEqualULPs_Smoke)
+UNIT_TEST(AlmostEqualULPs_double)
 {
   TEST_ALMOST_EQUAL_ULPS(3.0, 3.0, ());
   TEST_ALMOST_EQUAL_ULPS(+0.0, -0.0, ());
@@ -70,6 +70,30 @@ UNIT_TEST(AlmostEqualULPs_Smoke)
   TEST(!base::AlmostEqualULPs(0.0, eps), ());
 }
 
+UNIT_TEST(AlmostEqualULPs_float)
+{
+  TEST_ALMOST_EQUAL_ULPS(3.0f, 3.0f, ());
+  TEST_ALMOST_EQUAL_ULPS(+0.0f, -0.0f, ());
+
+  float const eps = std::numeric_limits<float>::epsilon();
+  float const dmax = std::numeric_limits<float>::max();
+
+  TEST_ALMOST_EQUAL_ULPS(1.0f + eps, 1.0f, ());
+  TEST_ALMOST_EQUAL_ULPS(1.0f - eps, 1.0f, ());
+  TEST_ALMOST_EQUAL_ULPS(1.0f - eps, 1.0f + eps, ());
+
+  TEST_ALMOST_EQUAL_ULPS(dmax, dmax, ());
+  TEST_ALMOST_EQUAL_ULPS(-dmax, -dmax, ());
+  TEST_ALMOST_EQUAL_ULPS(dmax/2.0f, dmax/2.0f, ());
+  TEST_ALMOST_EQUAL_ULPS(1.0f/dmax, 1.0f/dmax, ());
+  TEST_ALMOST_EQUAL_ULPS(-1.0f/dmax, -1.0f/dmax, ());
+
+  TEST(!base::AlmostEqualULPs(1.0f, -1.0f), ());
+  TEST(!base::AlmostEqualULPs(2.0f, -2.0f), ());
+  TEST(!base::AlmostEqualULPs(dmax, -dmax), ());
+  TEST(!base::AlmostEqualULPs(0.0f, eps), ());
+}
+
 UNIT_TEST(AlmostEqual_Smoke)
 {
   double const small = 1e-18;

base/math.cpp

@@ -0,0 +1,51 @@
+#include "math.hpp"
+
+#include <boost/integer.hpp>
+
+#include <cstring>
+#include <limits>
+
+namespace base
+{
+
+template <typename Float>
+bool AlmostEqualULPs(Float x, Float y, uint32_t maxULPs)
+{
+  static_assert(std::is_floating_point<Float>::value, "");
+  static_assert(std::numeric_limits<Float>::is_iec559, "");
+
+  // Make sure maxUlps is non-negative and small enough that the
+  // default NaN won't compare as equal to anything.
+  ASSERT_LESS(maxULPs, 4 * 1024 * 1024, ());
+
+  int constexpr bits = CHAR_BIT * sizeof(Float);
+  typedef typename boost::int_t<bits>::exact IntType;
+  typedef typename boost::uint_t<bits>::exact UIntType;
+
+  // Same as *reinterpret_cast<IntType const *>(&x), but without warnings.
+  IntType xInt, yInt;
+  static_assert(sizeof(xInt) == sizeof(x), "bit_cast impossible");
+  std::memcpy(&xInt, &x, sizeof(x));
+  std::memcpy(&yInt, &y, sizeof(y));
+
+  // Make xInt and yInt lexicographically ordered as a twos-complement int.
+  IntType const highestBit = IntType(1) << (bits - 1);
+  if (xInt < 0)
+    xInt = highestBit - xInt;
+  if (yInt < 0)
+    yInt = highestBit - yInt;
+
+  // Calculate diff with special case to avoid IntType overflow.
+  UIntType diff;
+  if ((xInt >= 0) == (yInt >= 0))
+    diff = Abs(xInt - yInt);
+  else
+    diff = UIntType(Abs(xInt)) + UIntType(Abs(yInt));
+
+  return diff <= maxULPs;
+}
+
+template bool AlmostEqualULPs<float>(float x, float y, uint32_t maxULPs);
+template bool AlmostEqualULPs<double>(double x, double y, uint32_t maxULPs);
+
+} // namespace base

base/math.hpp

@@ -2,16 +2,11 @@
 
 #include "base/assert.hpp"
 
-#include <algorithm>
+#include <algorithm>    // std::max
-#include <climits>
 #include <cmath>
-#include <cstring>
+#include <functional>   // std::hash
-#include <functional>
-#include <limits>
 #include <type_traits>
 
-#include <boost/integer.hpp>
-
 namespace math
 {
 double constexpr pi = 3.14159265358979323846;
@@ -44,33 +39,7 @@ int constexpr Sign(Number const number) noexcept
 // See https://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/
 // for details.
 template <typename Float>
-bool AlmostEqualULPs(Float x, Float y, unsigned int maxULPs = 256)
+bool AlmostEqualULPs(Float x, Float y, uint32_t maxULPs = 256);
-{
-  static_assert(std::is_floating_point<Float>::value, "");
-  static_assert(std::numeric_limits<Float>::is_iec559, "");
-
-  // Make sure maxUlps is non-negative and small enough that the
-  // default NaN won't compare as equal to anything.
-  ASSERT_LESS(maxULPs, 4 * 1024 * 1024, ());
-
-  int const bits = CHAR_BIT * sizeof(Float);
-  typedef typename boost::int_t<bits>::exact IntType;
-  typedef typename boost::uint_t<bits>::exact UIntType;
-  IntType xInt, yInt;
-  static_assert(sizeof(xInt) == sizeof(x), "bit_cast impossible");
-  std::memcpy(&xInt, &x, sizeof(x));
-  std::memcpy(&yInt, &y, sizeof(y));
-  // Make xInt and yInt lexicographically ordered as a twos-complement int
-  IntType const highestBit = IntType(1) << (bits - 1);
-  if (xInt < 0)
-    xInt = highestBit - xInt;
-  if (yInt < 0)
-    yInt = highestBit - yInt;
-
-  UIntType const diff = Abs(xInt - yInt);
-
-  return diff <= maxULPs;
-}
 
 // Returns true if x and y are equal up to the absolute difference eps.
 // Does not produce a sensible result if any of the arguments is NaN or infinity.

indexer/indexer_tests/read_features_tests.cpp

@@ -28,7 +28,6 @@ UNIT_TEST(ReadFeatures_Smoke)
   LOG(LINFO, (guard.GetNumFeatures()));
   for (uint32_t i = 0; i + 1 < guard.GetNumFeatures(); ++i)
   {
-    LOG(LINFO, ("Trying", i, i + 1));
     auto ft1 = guard.GetFeatureByIndex(i);
     auto ft2 = guard.GetFeatureByIndex(i + 1);
 

xcode/base/base.xcodeproj/project.pbxproj

@@ -144,6 +144,7 @@
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 		67B52B601AD3C84E00664C17 /* thread_checker.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 67B52B5E1AD3C84E00664C17 /* thread_checker.cpp */; };
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+		ACB634A3274D65F000F91940 /* math.cpp in Sources */ = {isa = PBXBuildFile; fileRef = ACB634A2274D65F000F91940 /* math.cpp */; };
 		E1B7FFC121FA19FE00F094DC /* thread_pool_computational.hpp in Headers */ = {isa = PBXBuildFile; fileRef = E1B7FFBD21FA19FD00F094DC /* thread_pool_computational.hpp */; };
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 		E1B7FFC321FA19FE00F094DC /* thread_utils.hpp in Headers */ = {isa = PBXBuildFile; fileRef = E1B7FFBF21FA19FD00F094DC /* thread_utils.hpp */; };
@@ -295,6 +296,7 @@
 		67B52B5F1AD3C84E00664C17 /* thread_checker.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = thread_checker.hpp; sourceTree = "<group>"; };
 		67C79B9E1E2929DB00C40034 /* checked_cast.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = checked_cast.hpp; sourceTree = "<group>"; };
 		67E40EC71E4DC0D500A6D200 /* small_set_test.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = small_set_test.cpp; sourceTree = "<group>"; };
+		ACB634A2274D65F000F91940 /* math.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = math.cpp; sourceTree = "<group>"; };
 		E1B7FFBD21FA19FD00F094DC /* thread_pool_computational.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = thread_pool_computational.hpp; sourceTree = "<group>"; };
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 		E1B7FFBF21FA19FD00F094DC /* thread_utils.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = thread_utils.hpp; sourceTree = "<group>"; };
@@ -440,6 +442,7 @@
 				6753419C1A3F57E400A0A8C3 /* lower_case.cpp */,
 				56290B89206D0887003892E0 /* lru_cache.hpp */,
 				6753419D1A3F57E400A0A8C3 /* macros.hpp */,
+				ACB634A2274D65F000F91940 /* math.cpp */,
 				6753419E1A3F57E400A0A8C3 /* math.hpp */,
 				6753419F1A3F57E400A0A8C3 /* matrix.hpp */,
 				672DD4B51E04255F0078E13C /* mem_trie.hpp */,
@@ -730,6 +733,7 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				ACB634A3274D65F000F91940 /* math.cpp in Sources */,
 				3446C6741DDCA96300146687 /* uni_string_dfa.cpp in Sources */,
 				3446C6721DDCA96300146687 /* levenshtein_dfa.cpp in Sources */,
 				390F1C0E2294298E00EA58E3 /* file_name_utils.cpp in Sources */,