Add xmx3, mulx2 with multipliers from https://arxiv.org/abs/2001.05304

benchmark/uint32.cpp

@@ -295,9 +295,15 @@ template<class K, class V> using boost_unordered_flat_map_xmx =
 template<class K, class V> using boost_unordered_flat_map_xmx2 =
     boost::unordered_flat_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>, boost::unordered::detail::foa::xmx2_mix>;
 
+template<class K, class V> using boost_unordered_flat_map_xmx3 =
+    boost::unordered_flat_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>, boost::unordered::detail::foa::xmx3_mix>;
+
 template<class K, class V> using boost_unordered_flat_map_mulx =
     boost::unordered_flat_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>, boost::unordered::detail::foa::mulx_mix>;
 
+template<class K, class V> using boost_unordered_flat_map_mulx2 =
+    boost::unordered_flat_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>, boost::unordered::detail::foa::mulx2_mix>;
+
 #ifdef HAVE_ABSEIL
 
 template<class K, class V> using absl_node_hash_map =
@@ -321,9 +327,12 @@ int main()
 
     test<std_unordered_map>( "std::unordered_map" );
     test<boost_unordered_map>( "boost::unordered_map" );
+
     test<boost_unordered_flat_map_xmx>( "boost::unordered_flat_map, xmx" );
     test<boost_unordered_flat_map_xmx2>( "boost::unordered_flat_map, xmx2" );
+    test<boost_unordered_flat_map_xmx3>( "boost::unordered_flat_map, xmx3" );
     test<boost_unordered_flat_map_mulx>( "boost::unordered_flat_map, mulx" );
+    test<boost_unordered_flat_map_mulx2>( "boost::unordered_flat_map, mulx2" );
 
 #ifdef HAVE_ANKERL_UNORDERED_DENSE
 

benchmark/uint64.cpp

@@ -295,9 +295,15 @@ template<class K, class V> using boost_unordered_flat_map_xmx =
 template<class K, class V> using boost_unordered_flat_map_xmx2 =
     boost::unordered_flat_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>, boost::unordered::detail::foa::xmx2_mix>;
 
+template<class K, class V> using boost_unordered_flat_map_xmx3 =
+    boost::unordered_flat_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>, boost::unordered::detail::foa::xmx3_mix>;
+
 template<class K, class V> using boost_unordered_flat_map_mulx =
     boost::unordered_flat_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>, boost::unordered::detail::foa::mulx_mix>;
 
+template<class K, class V> using boost_unordered_flat_map_mulx2 =
+    boost::unordered_flat_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>, boost::unordered::detail::foa::mulx2_mix>;
+
 #ifdef HAVE_ABSEIL
 
 template<class K, class V> using absl_node_hash_map =
@@ -331,9 +337,12 @@ int main()
 #endif
 
     test<boost_unordered_map>( "boost::unordered_map" );
+
     test<boost_unordered_flat_map_xmx>( "boost::unordered_flat_map, xmx" );
     test<boost_unordered_flat_map_xmx2>( "boost::unordered_flat_map, xmx2" );
+    test<boost_unordered_flat_map_xmx3>( "boost::unordered_flat_map, xmx3" );
     test<boost_unordered_flat_map_mulx>( "boost::unordered_flat_map, mulx" );
+    test<boost_unordered_flat_map_mulx2>( "boost::unordered_flat_map, mulx2" );
 
 #ifdef HAVE_ANKERL_UNORDERED_DENSE
 

benchmark/uuid.cpp

@@ -346,9 +346,15 @@ template<class K, class V> using boost_unordered_flat_map_xmx =
 template<class K, class V> using boost_unordered_flat_map_xmx2 =
     boost::unordered_flat_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>, boost::unordered::detail::foa::xmx2_mix>;
 
+template<class K, class V> using boost_unordered_flat_map_xmx3 =
+    boost::unordered_flat_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>, boost::unordered::detail::foa::xmx3_mix>;
+
 template<class K, class V> using boost_unordered_flat_map_mulx =
     boost::unordered_flat_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>, boost::unordered::detail::foa::mulx_mix>;
 
+template<class K, class V> using boost_unordered_flat_map_mulx2 =
+    boost::unordered_flat_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>, boost::unordered::detail::foa::mulx2_mix>;
+
 #ifdef HAVE_ABSEIL
 
 template<class K, class V> using absl_node_hash_map =
@@ -372,9 +378,12 @@ int main()
 
     test<std_unordered_map>( "std::unordered_map" );
     test<boost_unordered_map>( "boost::unordered_map" );
+
     test<boost_unordered_flat_map_xmx>( "boost::unordered_flat_map, xmx" );
     test<boost_unordered_flat_map_xmx2>( "boost::unordered_flat_map, xmx2" );
+    test<boost_unordered_flat_map_xmx3>( "boost::unordered_flat_map, xmx3" );
     test<boost_unordered_flat_map_mulx>( "boost::unordered_flat_map, mulx" );
+    test<boost_unordered_flat_map_mulx2>( "boost::unordered_flat_map, mulx2" );
 
 #ifdef HAVE_ANKERL_UNORDERED_DENSE
 

benchmark/word_size.cpp

@@ -187,9 +187,15 @@ template<class K, class V> using boost_unordered_flat_map_xmx =
 template<class K, class V> using boost_unordered_flat_map_xmx2 =
     boost::unordered_flat_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>, boost::unordered::detail::foa::xmx2_mix>;
 
+template<class K, class V> using boost_unordered_flat_map_xmx3 =
+    boost::unordered_flat_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>, boost::unordered::detail::foa::xmx3_mix>;
+
 template<class K, class V> using boost_unordered_flat_map_mulx =
     boost::unordered_flat_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>, boost::unordered::detail::foa::mulx_mix>;
 
+template<class K, class V> using boost_unordered_flat_map_mulx2 =
+    boost::unordered_flat_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>, boost::unordered::detail::foa::mulx2_mix>;
+
 #ifdef HAVE_ABSEIL
 
 template<class K, class V> using absl_node_hash_map =
@@ -213,9 +219,12 @@ int main()
 
     test<std_unordered_map>( "std::unordered_map" );
     test<boost_unordered_map>( "boost::unordered_map" );
+
     test<boost_unordered_flat_map_xmx>( "boost::unordered_flat_map, xmx" );
     test<boost_unordered_flat_map_xmx2>( "boost::unordered_flat_map, xmx2" );
+    test<boost_unordered_flat_map_xmx3>( "boost::unordered_flat_map, xmx3" );
     test<boost_unordered_flat_map_mulx>( "boost::unordered_flat_map, mulx" );
+    test<boost_unordered_flat_map_mulx2>( "boost::unordered_flat_map, mulx2" );
 
 #ifdef HAVE_ANKERL_UNORDERED_DENSE
 

include/boost/unordered/detail/foa.hpp

@@ -770,6 +770,15 @@ struct xmx2_mix
   }
 };
 
+struct xmx3_mix
+{
+  template<typename Hash,typename T>
+  static inline std::size_t mix(const Hash& h,const T& x)
+  {
+    return xmx3(h(x));
+  }
+};
+
 struct mulx_mix
 {
   template<typename Hash,typename T>
@@ -779,6 +788,15 @@ struct mulx_mix
   }
 };
 
+struct mulx2_mix
+{
+  template<typename Hash,typename T>
+  static inline std::size_t mix(const Hash& h,const T& x)
+  {
+    return mulx2(h(x));
+  }
+};
+
 /* boost::core::countr_zero has a potentially costly check for
  * the case x==0.
  */

include/boost/unordered/detail/mulx.hpp

@@ -94,6 +94,8 @@ inline boost::uint32_t mulx32( boost::uint32_t x, boost::uint32_t y )
 #endif
 #endif
 
+// phi multipliers
+
 inline std::size_t mulx( std::size_t x ) noexcept
 {
 #if defined(BOOST_UNORDERED_64B_ARCHITECTURE)
@@ -107,6 +109,21 @@ inline std::size_t mulx( std::size_t x ) noexcept
 #endif
 }
 
+// multipliers from https://arxiv.org/abs/2001.05304
+
+inline std::size_t mulx2( std::size_t x ) noexcept
+{
+#if defined(BOOST_UNORDERED_64B_ARCHITECTURE)
+
+    return (std::size_t)mulx64( (boost::uint64_t)x, 0xDEFBA91144F2B375ull );
+
+#else /* 32 bits assumed */
+
+    return mulx32( x, 0xE817FB2Du );
+
+#endif
+}
+
 #ifdef BOOST_UNORDERED_64B_ARCHITECTURE
 #undef BOOST_UNORDERED_64B_ARCHITECTURE
 #endif

include/boost/unordered/detail/xmx.hpp

@@ -64,7 +64,7 @@ static inline std::size_t xmx(std::size_t x)noexcept
 #endif
 }
 
-// alternative multipliers
+// alternative multipliers (phi)
 
 static inline std::size_t xmx2( std::size_t x ) noexcept
 {
@@ -89,6 +89,31 @@ static inline std::size_t xmx2( std::size_t x ) noexcept
 #endif
 }
 
+// alternative multipliers (https://arxiv.org/abs/2001.05304)
+
+static inline std::size_t xmx3( std::size_t x ) noexcept
+{
+#if defined(BOOST_UNORDERED_64B_ARCHITECTURE)
+
+  boost::uint64_t z=(boost::uint64_t)x;
+
+  z ^= z >> 23;
+  z *= 0xF1357AEA2E62A9C5ull;
+  z ^= z >> 23;
+
+  return (std::size_t)z;
+
+#else /* 32 bits assumed */
+
+  x ^= x >> 18;
+  x *= 0x93D765DDu;
+  x ^= x >> 16;
+
+  return x;
+
+#endif
+}
+
 #ifdef BOOST_UNORDERED_64B_ARCHITECTURE
 #undef BOOST_UNORDERED_64B_ARCHITECTURE
 #endif