[libcxx-commits] [libcxx] [libc++] Extend the scope of radix sorting inside std::stable_sort to floating-point types (PR #129452)
Дмитрий Изволов via libcxx-commits
libcxx-commits at lists.llvm.org
Tue Mar 25 11:38:53 PDT 2025
https://github.com/izvolov updated https://github.com/llvm/llvm-project/pull/129452
>From d1251a46558b4a070e8cc3be327b5e90fdaba251 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=94=D0=BC=D0=B8=D1=82=D1=80=D0=B8=D0=B9=20=D0=98=D0=B7?=
=?UTF-8?q?=D0=B2=D0=BE=D0=BB=D0=BE=D0=B2?= <dmitriy at izvolov.ru>
Date: Fri, 31 Jan 2025 01:13:50 +0300
Subject: [PATCH 01/12] sort-scalars
---
libcxx/include/__algorithm/radix_sort.h | 97 +++++++++++++++++++++++-
libcxx/include/__algorithm/stable_sort.h | 20 ++---
2 files changed, 107 insertions(+), 10 deletions(-)
diff --git a/libcxx/include/__algorithm/radix_sort.h b/libcxx/include/__algorithm/radix_sort.h
index f6d9fb1ad7ca9..a8d355016e77e 100644
--- a/libcxx/include/__algorithm/radix_sort.h
+++ b/libcxx/include/__algorithm/radix_sort.h
@@ -29,9 +29,11 @@
#include <__algorithm/for_each.h>
#include <__algorithm/move.h>
+#include <__bit/bit_cast.h>
#include <__bit/bit_log2.h>
#include <__bit/countl.h>
#include <__config>
+#include <__cstddef/size_t.h>
#include <__functional/identity.h>
#include <__iterator/access.h>
#include <__iterator/distance.h>
@@ -44,9 +46,12 @@
#include <__type_traits/enable_if.h>
#include <__type_traits/invoke.h>
#include <__type_traits/is_assignable.h>
+#include <__type_traits/is_enum.h>
+#include <__type_traits/is_floating_point.h>
#include <__type_traits/is_integral.h>
#include <__type_traits/is_unsigned.h>
#include <__type_traits/make_unsigned.h>
+#include <__type_traits/underlying_type.h>
#include <__utility/forward.h>
#include <__utility/integer_sequence.h>
#include <__utility/move.h>
@@ -298,6 +303,94 @@ _LIBCPP_HIDE_FROM_ABI constexpr auto __shift_to_unsigned(_Ip __n) {
return static_cast<make_unsigned_t<_Ip> >(__n ^ __min_value);
}
+template <size_t _Size>
+struct __unsigned_integer_of_size {};
+
+template <>
+struct __unsigned_integer_of_size<1> {
+ using type = uint8_t;
+};
+
+template <>
+struct __unsigned_integer_of_size<2> {
+ using type = uint16_t;
+};
+
+template <>
+struct __unsigned_integer_of_size<4> {
+ using type = uint32_t;
+};
+
+template <>
+struct __unsigned_integer_of_size<8> {
+ using type = uint64_t;
+};
+
+template <>
+struct __unsigned_integer_of_size<16> {
+# if _LIBCPP_HAS_INT128
+ using type = __int128;
+# endif
+};
+
+template <size_t _Size>
+using __unsigned_integer_of_size_t _LIBCPP_NODEBUG = typename __unsigned_integer_of_size<_Size>::type;
+
+template <class _Sc>
+using __unsigned_representation_for_t _LIBCPP_NODEBUG = __unsigned_integer_of_size_t<sizeof(_Sc)>;
+
+// Represent a scalar type as an ordered integer
+
+// The function is defined for ordered scalar types: integers, floating-point numbers, pointers, and enums.
+// Returns an integer representation such that for any `x` and `y` such that `x < y`, the expression
+// `__to_ordered_integral(x) < __to_ordered_integral(y)` is true, where `x`, `y` are values of the `Scalar` type.
+// __unsigned_representation_for_t<_Scalar> __to_ordered_integral(_Scalar);
+
+template <class _Integral, enable_if_t< is_integral<_Integral>::value, int> = 0>
+_LIBCPP_HIDE_FROM_ABI constexpr auto __to_ordered_integral(_Integral __n) {
+ return __n;
+}
+
+// An overload for floating-point numbers
+
+// From the IEEE 754 standard, we know that:
+// 1. The bit representation of positive floats directly reflects their order:
+// When comparing floats by magnitude, the number with the larger exponent is greater, and if the exponents are
+// equal, the one with the larger mantissa is greater.
+// 2. The bit representation of negative floats reflects their reverse order (for the same reasons).
+// 3. The most significant bit (sign bit) is zero for positive floats and one for negative floats. Therefore, in the raw
+// bit representation, any negative number will be greater than any positive number.
+
+// The only exception from this rule is `NaN`, which is unordered by definition.
+
+// Based on the above, to obtain correctly ordered integral representation of floating-point numbers, we need to:
+// 1. Invert the bit representation (including the sign bit) of negative floats to switch from reverse order to direct
+// order;
+// 2. Invert the sign bit for positive floats.
+
+// Thus, in final integral representation, we have reversed the order for negative floats and made all negative floats
+// smaller than all positive numbers (by inverting the sign bit).
+template <class _Floating, enable_if_t< is_floating_point<_Floating>::value, int> = 0>
+_LIBCPP_HIDE_FROM_ABI constexpr auto __to_ordered_integral(_Floating __f) {
+ using __integral_type = __unsigned_representation_for_t<_Floating>;
+ constexpr auto __bit_count = std::numeric_limits<__integral_type>::digits;
+ constexpr auto __sign_bit_mask = static_cast<__integral_type>(__integral_type{1} << (__bit_count - 1));
+
+ const auto __u = std::__bit_cast<__integral_type>(__f);
+
+ return static_cast<__integral_type>(__u & __sign_bit_mask ? ~__u : __u ^ __sign_bit_mask);
+}
+
+template <class _Enum, enable_if_t< is_enum<_Enum>::value, int> = 0>
+_LIBCPP_HIDE_FROM_ABI constexpr auto __to_ordered_integral(_Enum __e) {
+ return static_cast<std::underlying_type_t<_Enum>>(__e);
+}
+
+template <class _Pointer>
+_LIBCPP_HIDE_FROM_ABI constexpr auto __to_ordered_integral(_Pointer* __ptr) {
+ return std::__bit_cast<__unsigned_representation_for_t<_Pointer*>>(__ptr);
+}
+
struct __low_byte_fn {
template <class _Ip>
_LIBCPP_HIDE_FROM_ABI constexpr uint8_t operator()(_Ip __integer) const {
@@ -314,7 +407,9 @@ __radix_sort(_RandomAccessIterator1 __first,
_RandomAccessIterator2 __buffer,
_Map __map,
_Radix __radix) {
- auto __map_to_unsigned = [__map = std::move(__map)](const auto& __x) { return std::__shift_to_unsigned(__map(__x)); };
+ auto __map_to_unsigned = [__map = std::move(__map)](const auto& __x) {
+ return std::__shift_to_unsigned(__map(std::__to_ordered_integral(__x)));
+ };
std::__radix_sort_impl(__first, __last, __buffer, __map_to_unsigned, __radix);
}
diff --git a/libcxx/include/__algorithm/stable_sort.h b/libcxx/include/__algorithm/stable_sort.h
index 76d9e5557008f..2eb62b5230b32 100644
--- a/libcxx/include/__algorithm/stable_sort.h
+++ b/libcxx/include/__algorithm/stable_sort.h
@@ -25,9 +25,10 @@
#include <__memory/unique_temporary_buffer.h>
#include <__type_traits/desugars_to.h>
#include <__type_traits/enable_if.h>
+#include <__type_traits/invoke.h>
#include <__type_traits/is_constant_evaluated.h>
-#include <__type_traits/is_integral.h>
#include <__type_traits/is_same.h>
+#include <__type_traits/is_scalar.h>
#include <__type_traits/is_trivially_assignable.h>
#include <__type_traits/remove_cvref.h>
#include <__utility/move.h>
@@ -202,7 +203,7 @@ struct __stable_sort_switch {
#if _LIBCPP_STD_VER >= 17
template <class _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr unsigned __radix_sort_min_bound() {
- static_assert(is_integral<_Tp>::value);
+ static_assert(is_scalar<_Tp>::value);
if constexpr (sizeof(_Tp) == 1) {
return 1 << 8;
}
@@ -212,13 +213,14 @@ _LIBCPP_HIDE_FROM_ABI constexpr unsigned __radix_sort_min_bound() {
template <class _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr unsigned __radix_sort_max_bound() {
- static_assert(is_integral<_Tp>::value);
+ static_assert(is_scalar<_Tp>::value);
if constexpr (sizeof(_Tp) >= 8) {
return 1 << 15;
}
return 1 << 16;
}
+
#endif // _LIBCPP_STD_VER >= 17
template <class _AlgPolicy, class _Compare, class _RandomAccessIterator>
@@ -246,12 +248,12 @@ _LIBCPP_CONSTEXPR_SINCE_CXX26 void __stable_sort(
}
#if _LIBCPP_STD_VER >= 17
- constexpr auto __default_comp =
- __desugars_to_v<__totally_ordered_less_tag, __remove_cvref_t<_Compare>, value_type, value_type >;
- constexpr auto __integral_value =
- is_integral_v<value_type > && is_same_v< value_type&, __iter_reference<_RandomAccessIterator>>;
- constexpr auto __allowed_radix_sort = __default_comp && __integral_value;
- if constexpr (__allowed_radix_sort) {
+ constexpr auto __default_comp = __desugars_to_v<__less_tag, __remove_cvref_t<_Compare>, value_type, value_type >;
+ constexpr auto __scalar_value =
+ is_scalar_v<value_type > && is_same_v< value_type&, __iter_reference<_RandomAccessIterator>>;
+ // There are non-comparable scalars (std::nullptr_t, pointers to members), so we need to exclude them.
+ constexpr auto __comparable_value = is_invocable_r_v<bool, _Compare, value_type, value_type>;
+ if constexpr (__default_comp && __scalar_value && __comparable_value) {
if (__len <= __buff_size && __len >= static_cast<difference_type>(std::__radix_sort_min_bound<value_type>()) &&
__len <= static_cast<difference_type>(std::__radix_sort_max_bound<value_type>())) {
if (__libcpp_is_constant_evaluated()) {
>From d06a76247c81f44920a40ecf54e7a28ead975ed9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=94=D0=BC=D0=B8=D1=82=D1=80=D0=B8=D0=B9=20=D0=98=D0=B7?=
=?UTF-8?q?=D0=B2=D0=BE=D0=BB=D0=BE=D0=B2?= <dmitriy at izvolov.ru>
Date: Wed, 5 Feb 2025 22:59:15 +0300
Subject: [PATCH 02/12] improve-tests-for-floats
---
.../alg.sort/stable.sort/stable_sort.pass.cpp | 36 ++++++++++++++++++-
1 file changed, 35 insertions(+), 1 deletion(-)
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp
index 4ee1d795a23b2..d18f956863904 100644
--- a/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp
@@ -18,6 +18,7 @@
#include <algorithm>
#include <cassert>
#include <iterator>
+#include <limits>
#include <random>
#include <vector>
@@ -68,6 +69,13 @@ TEST_CONSTEXPR_CXX26 std::vector<T> generate_sawtooth(int N, int M) {
if (++x == M)
x = 0;
}
+
+ if (std::is_signed<T>::value) {
+ for (auto& a : v) {
+ a -= (M / 2);
+ }
+ }
+
return v;
}
@@ -193,12 +201,38 @@ TEST_CONSTEXPR_CXX26 bool test() {
return true;
}
+template <class T>
+bool test_floating_special_values() {
+ static_assert(std::is_floating_point<T>::value, "");
+
+ auto v = generate_sawtooth<T>(1024, 512);
+ v.insert(v.end(), 256, static_cast<T>(0.0));
+ v.insert(v.end(), 256, static_cast<T>(-0.0));
+ v.insert(v.end(), 256, std::numeric_limits<T>::infinity());
+ v.insert(v.end(), 256, -std::numeric_limits<T>::infinity());
+
+ std::mt19937 randomness;
+ std::shuffle(v.begin(), v.end(), randomness);
+
+ std::stable_sort(v.begin(), v.end());
+ assert(std::is_sorted(v.begin(), v.end()));
+
+ return true;
+}
+
+template <class T>
+bool test_floating() {
+ return test<T>() && test_floating_special_values<T>();
+}
+
int main(int, char**) {
test<int>();
- test<float>();
+ test_floating<float>();
+ test_floating<double>();
#if TEST_STD_VER >= 26
static_assert(test<int>());
static_assert(test<float>());
+ static_assert(test<double>());
// test constexprness of radix sort branch
static_assert(test<char>());
#endif
>From 6aeb04d8c9cdb46658f81d85e841caac3b1ad89d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=94=D0=BC=D0=B8=D1=82=D1=80=D0=B8=D0=B9=20=D0=98=D0=B7?=
=?UTF-8?q?=D0=B2=D0=BE=D0=BB=D0=BE=D0=B2?= <dmitriy at izvolov.ru>
Date: Mon, 3 Mar 2025 21:48:46 +0300
Subject: [PATCH 03/12] arithmetic-only
---
libcxx/include/__algorithm/radix_sort.h | 10 ++-------
libcxx/include/__algorithm/stable_sort.h | 14 ++++++-------
.../alg.sort/stable.sort/stable_sort.pass.cpp | 21 +++++++++++++++++++
3 files changed, 29 insertions(+), 16 deletions(-)
diff --git a/libcxx/include/__algorithm/radix_sort.h b/libcxx/include/__algorithm/radix_sort.h
index a8d355016e77e..ed6215a3bbd85 100644
--- a/libcxx/include/__algorithm/radix_sort.h
+++ b/libcxx/include/__algorithm/radix_sort.h
@@ -381,15 +381,9 @@ _LIBCPP_HIDE_FROM_ABI constexpr auto __to_ordered_integral(_Floating __f) {
return static_cast<__integral_type>(__u & __sign_bit_mask ? ~__u : __u ^ __sign_bit_mask);
}
+// There may exist user-defined comparison for enum, so we cannot compare enums just like integers.
template <class _Enum, enable_if_t< is_enum<_Enum>::value, int> = 0>
-_LIBCPP_HIDE_FROM_ABI constexpr auto __to_ordered_integral(_Enum __e) {
- return static_cast<std::underlying_type_t<_Enum>>(__e);
-}
-
-template <class _Pointer>
-_LIBCPP_HIDE_FROM_ABI constexpr auto __to_ordered_integral(_Pointer* __ptr) {
- return std::__bit_cast<__unsigned_representation_for_t<_Pointer*>>(__ptr);
-}
+_LIBCPP_HIDE_FROM_ABI constexpr auto __to_ordered_integral(_Enum __e) = delete;
struct __low_byte_fn {
template <class _Ip>
diff --git a/libcxx/include/__algorithm/stable_sort.h b/libcxx/include/__algorithm/stable_sort.h
index 2eb62b5230b32..387db68a6b7d1 100644
--- a/libcxx/include/__algorithm/stable_sort.h
+++ b/libcxx/include/__algorithm/stable_sort.h
@@ -26,9 +26,9 @@
#include <__type_traits/desugars_to.h>
#include <__type_traits/enable_if.h>
#include <__type_traits/invoke.h>
+#include <__type_traits/is_arithmetic.h>
#include <__type_traits/is_constant_evaluated.h>
#include <__type_traits/is_same.h>
-#include <__type_traits/is_scalar.h>
#include <__type_traits/is_trivially_assignable.h>
#include <__type_traits/remove_cvref.h>
#include <__utility/move.h>
@@ -203,7 +203,7 @@ struct __stable_sort_switch {
#if _LIBCPP_STD_VER >= 17
template <class _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr unsigned __radix_sort_min_bound() {
- static_assert(is_scalar<_Tp>::value);
+ static_assert(is_arithmetic<_Tp>::value);
if constexpr (sizeof(_Tp) == 1) {
return 1 << 8;
}
@@ -213,7 +213,7 @@ _LIBCPP_HIDE_FROM_ABI constexpr unsigned __radix_sort_min_bound() {
template <class _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr unsigned __radix_sort_max_bound() {
- static_assert(is_scalar<_Tp>::value);
+ static_assert(is_arithmetic<_Tp>::value);
if constexpr (sizeof(_Tp) >= 8) {
return 1 << 15;
}
@@ -249,11 +249,9 @@ _LIBCPP_CONSTEXPR_SINCE_CXX26 void __stable_sort(
#if _LIBCPP_STD_VER >= 17
constexpr auto __default_comp = __desugars_to_v<__less_tag, __remove_cvref_t<_Compare>, value_type, value_type >;
- constexpr auto __scalar_value =
- is_scalar_v<value_type > && is_same_v< value_type&, __iter_reference<_RandomAccessIterator>>;
- // There are non-comparable scalars (std::nullptr_t, pointers to members), so we need to exclude them.
- constexpr auto __comparable_value = is_invocable_r_v<bool, _Compare, value_type, value_type>;
- if constexpr (__default_comp && __scalar_value && __comparable_value) {
+ constexpr auto __arithmetic_value =
+ is_arithmetic_v<value_type > && is_same_v< value_type&, __iter_reference<_RandomAccessIterator>>;
+ if constexpr (__default_comp && __arithmetic_value) {
if (__len <= __buff_size && __len >= static_cast<difference_type>(std::__radix_sort_min_bound<value_type>()) &&
__len <= static_cast<difference_type>(std::__radix_sort_max_bound<value_type>())) {
if (__libcpp_is_constant_evaluated()) {
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp
index d18f956863904..ef150b19dd814 100644
--- a/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp
@@ -225,10 +225,31 @@ bool test_floating() {
return test<T>() && test_floating_special_values<T>();
}
+enum struct Enum : int { a, b, c, d, e, f, g, h };
+TEST_CONSTEXPR_CXX26 bool operator<(Enum x, Enum y) { return static_cast<int>(x) > static_cast<int>(y); }
+
+TEST_CONSTEXPR_CXX26 bool test_enum() {
+ auto v = std::vector<Enum>(128, Enum::a);
+ v.resize(v.size() + 128, Enum::b);
+ v.resize(v.size() + 128, Enum::c);
+ v.resize(v.size() + 128, Enum::d);
+ v.resize(v.size() + 128, Enum::e);
+ v.resize(v.size() + 128, Enum::f);
+ v.resize(v.size() + 128, Enum::g);
+ v.resize(v.size() + 128, Enum::h);
+
+ // Order is reversed by definition
+ std::stable_sort(v.begin(), v.end());
+ assert(std::is_sorted(v.begin(), v.end()));
+
+ return true;
+}
+
int main(int, char**) {
test<int>();
test_floating<float>();
test_floating<double>();
+ test_enum();
#if TEST_STD_VER >= 26
static_assert(test<int>());
static_assert(test<float>());
>From 9d2e737cfdf7544fe6952ba74984a854afe4cdc9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=94=D0=BC=D0=B8=D1=82=D1=80=D0=B8=D0=B9=20=D0=98=D0=B7?=
=?UTF-8?q?=D0=B2=D0=BE=D0=BB=D0=BE=D0=B2?= <dmitriy at izvolov.ru>
Date: Mon, 3 Mar 2025 22:36:40 +0300
Subject: [PATCH 04/12] include
---
.../alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp | 1 +
1 file changed, 1 insertion(+)
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp
index ef150b19dd814..7691b2c5874ea 100644
--- a/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp
@@ -20,6 +20,7 @@
#include <iterator>
#include <limits>
#include <random>
+#include <type_traits>
#include <vector>
#include "count_new.h"
>From 44a06b6c437e85676e8652b9c0e71e71252ac46d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=94=D0=BC=D0=B8=D1=82=D1=80=D0=B8=D0=B9=20=D0=98=D0=B7?=
=?UTF-8?q?=D0=B2=D0=BE=D0=BB=D0=BE=D0=B2?= <dmitriy at izvolov.ru>
Date: Mon, 3 Mar 2025 23:36:33 +0300
Subject: [PATCH 05/12] include
---
libcxx/include/__algorithm/radix_sort.h | 1 -
1 file changed, 1 deletion(-)
diff --git a/libcxx/include/__algorithm/radix_sort.h b/libcxx/include/__algorithm/radix_sort.h
index ed6215a3bbd85..d330bef7a10c6 100644
--- a/libcxx/include/__algorithm/radix_sort.h
+++ b/libcxx/include/__algorithm/radix_sort.h
@@ -51,7 +51,6 @@
#include <__type_traits/is_integral.h>
#include <__type_traits/is_unsigned.h>
#include <__type_traits/make_unsigned.h>
-#include <__type_traits/underlying_type.h>
#include <__utility/forward.h>
#include <__utility/integer_sequence.h>
#include <__utility/move.h>
>From ebd025419cdeb4a7c062da639dbde07d93f2da04 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=94=D0=BC=D0=B8=D1=82=D1=80=D0=B8=D0=B9=20=D0=98=D0=B7?=
=?UTF-8?q?=D0=B2=D0=BE=D0=BB=D0=BE=D0=B2?= <dmitriy at izvolov.ru>
Date: Mon, 3 Mar 2025 23:42:37 +0300
Subject: [PATCH 06/12] exclude-non-ieee-754
---
libcxx/include/__algorithm/radix_sort.h | 7 +++----
libcxx/include/__algorithm/stable_sort.h | 6 ++++--
2 files changed, 7 insertions(+), 6 deletions(-)
diff --git a/libcxx/include/__algorithm/radix_sort.h b/libcxx/include/__algorithm/radix_sort.h
index d330bef7a10c6..82b94c2beaced 100644
--- a/libcxx/include/__algorithm/radix_sort.h
+++ b/libcxx/include/__algorithm/radix_sort.h
@@ -47,7 +47,6 @@
#include <__type_traits/invoke.h>
#include <__type_traits/is_assignable.h>
#include <__type_traits/is_enum.h>
-#include <__type_traits/is_floating_point.h>
#include <__type_traits/is_integral.h>
#include <__type_traits/is_unsigned.h>
#include <__type_traits/make_unsigned.h>
@@ -350,9 +349,9 @@ _LIBCPP_HIDE_FROM_ABI constexpr auto __to_ordered_integral(_Integral __n) {
return __n;
}
-// An overload for floating-point numbers
+// An overload for IEEE 754 floating-point numbers
-// From the IEEE 754 standard, we know that:
+// For the floats conforming to IEEE 754 (IEC 559) standard, we know that:
// 1. The bit representation of positive floats directly reflects their order:
// When comparing floats by magnitude, the number with the larger exponent is greater, and if the exponents are
// equal, the one with the larger mantissa is greater.
@@ -369,7 +368,7 @@ _LIBCPP_HIDE_FROM_ABI constexpr auto __to_ordered_integral(_Integral __n) {
// Thus, in final integral representation, we have reversed the order for negative floats and made all negative floats
// smaller than all positive numbers (by inverting the sign bit).
-template <class _Floating, enable_if_t< is_floating_point<_Floating>::value, int> = 0>
+template <class _Floating, enable_if_t< numeric_limits<_Floating>::is_iec559, int> = 0>
_LIBCPP_HIDE_FROM_ABI constexpr auto __to_ordered_integral(_Floating __f) {
using __integral_type = __unsigned_representation_for_t<_Floating>;
constexpr auto __bit_count = std::numeric_limits<__integral_type>::digits;
diff --git a/libcxx/include/__algorithm/stable_sort.h b/libcxx/include/__algorithm/stable_sort.h
index 387db68a6b7d1..03a139faad788 100644
--- a/libcxx/include/__algorithm/stable_sort.h
+++ b/libcxx/include/__algorithm/stable_sort.h
@@ -26,13 +26,14 @@
#include <__type_traits/desugars_to.h>
#include <__type_traits/enable_if.h>
#include <__type_traits/invoke.h>
-#include <__type_traits/is_arithmetic.h>
#include <__type_traits/is_constant_evaluated.h>
+#include <__type_traits/is_integral.h>
#include <__type_traits/is_same.h>
#include <__type_traits/is_trivially_assignable.h>
#include <__type_traits/remove_cvref.h>
#include <__utility/move.h>
#include <__utility/pair.h>
+#include <limits>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
@@ -250,7 +251,8 @@ _LIBCPP_CONSTEXPR_SINCE_CXX26 void __stable_sort(
#if _LIBCPP_STD_VER >= 17
constexpr auto __default_comp = __desugars_to_v<__less_tag, __remove_cvref_t<_Compare>, value_type, value_type >;
constexpr auto __arithmetic_value =
- is_arithmetic_v<value_type > && is_same_v< value_type&, __iter_reference<_RandomAccessIterator>>;
+ (is_integral_v<value_type > || numeric_limits<value_type>::is_iec559) &&
+ is_same_v< value_type&, __iter_reference<_RandomAccessIterator>>;
if constexpr (__default_comp && __arithmetic_value) {
if (__len <= __buff_size && __len >= static_cast<difference_type>(std::__radix_sort_min_bound<value_type>()) &&
__len <= static_cast<difference_type>(std::__radix_sort_max_bound<value_type>())) {
>From 28b48672474add1f5e448e0b3a4b21c18441fe34 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=94=D0=BC=D0=B8=D1=82=D1=80=D0=B8=D0=B9=20=D0=98=D0=B7?=
=?UTF-8?q?=D0=B2=D0=BE=D0=BB=D0=BE=D0=B2?= <dmitriy at izvolov.ru>
Date: Wed, 5 Mar 2025 10:46:44 +0300
Subject: [PATCH 07/12] comment
---
libcxx/include/__algorithm/radix_sort.h | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/libcxx/include/__algorithm/radix_sort.h b/libcxx/include/__algorithm/radix_sort.h
index 82b94c2beaced..995b1fea7a6bb 100644
--- a/libcxx/include/__algorithm/radix_sort.h
+++ b/libcxx/include/__algorithm/radix_sort.h
@@ -337,13 +337,9 @@ using __unsigned_integer_of_size_t _LIBCPP_NODEBUG = typename __unsigned_integer
template <class _Sc>
using __unsigned_representation_for_t _LIBCPP_NODEBUG = __unsigned_integer_of_size_t<sizeof(_Sc)>;
-// Represent a scalar type as an ordered integer
-
-// The function is defined for ordered scalar types: integers, floating-point numbers, pointers, and enums.
+// The function `__to_ordered_integral` is defined for integers and IEEE 754 floating-point numbers.
// Returns an integer representation such that for any `x` and `y` such that `x < y`, the expression
-// `__to_ordered_integral(x) < __to_ordered_integral(y)` is true, where `x`, `y` are values of the `Scalar` type.
-// __unsigned_representation_for_t<_Scalar> __to_ordered_integral(_Scalar);
-
+// `__to_ordered_integral(x) < __to_ordered_integral(y)` is true, where `x`, `y` are integers or IEEE 754 floats.
template <class _Integral, enable_if_t< is_integral<_Integral>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI constexpr auto __to_ordered_integral(_Integral __n) {
return __n;
>From ec0ede8b436662929a03341c71ffa29e547ddbfc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=94=D0=BC=D0=B8=D1=82=D1=80=D0=B8=D0=B9=20=D0=98=D0=B7?=
=?UTF-8?q?=D0=B2=D0=BE=D0=BB=D0=BE=D0=B2?= <dmitriy at izvolov.ru>
Date: Wed, 5 Mar 2025 13:28:33 +0300
Subject: [PATCH 08/12] release-notes
---
libcxx/docs/ReleaseNotes/21.rst | 3 +++
1 file changed, 3 insertions(+)
diff --git a/libcxx/docs/ReleaseNotes/21.rst b/libcxx/docs/ReleaseNotes/21.rst
index e7cfa625a132c..b97d2172fa836 100644
--- a/libcxx/docs/ReleaseNotes/21.rst
+++ b/libcxx/docs/ReleaseNotes/21.rst
@@ -52,6 +52,9 @@ Improvements and New Features
- Updated formatting library to Unicode 16.0.0.
+- The ``std::stable_sort`` algorithm uses radix sort for floating-point types now, which can improve the performance
+ up to 10 times, depending on type of sorted elements and the initial state of the sorted array.
+
Deprecations and Removals
-------------------------
>From 61cb9252fae75d0143daef104991db951fdadb26 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=94=D0=BC=D0=B8=D1=82=D1=80=D0=B8=D0=B9=20=D0=98=D0=B7?=
=?UTF-8?q?=D0=B2=D0=BE=D0=BB=D0=BE=D0=B2?= <dmitriy at izvolov.ru>
Date: Sat, 8 Mar 2025 17:57:33 +0300
Subject: [PATCH 09/12] tidy
---
libcxx/include/__algorithm/stable_sort.h | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/libcxx/include/__algorithm/stable_sort.h b/libcxx/include/__algorithm/stable_sort.h
index 03a139faad788..4c69eb78bd683 100644
--- a/libcxx/include/__algorithm/stable_sort.h
+++ b/libcxx/include/__algorithm/stable_sort.h
@@ -25,7 +25,6 @@
#include <__memory/unique_temporary_buffer.h>
#include <__type_traits/desugars_to.h>
#include <__type_traits/enable_if.h>
-#include <__type_traits/invoke.h>
#include <__type_traits/is_constant_evaluated.h>
#include <__type_traits/is_integral.h>
#include <__type_traits/is_same.h>
@@ -204,7 +203,7 @@ struct __stable_sort_switch {
#if _LIBCPP_STD_VER >= 17
template <class _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr unsigned __radix_sort_min_bound() {
- static_assert(is_arithmetic<_Tp>::value);
+ static_assert(is_integral_v<_Tp > || numeric_limits<_Tp>::is_iec559);
if constexpr (sizeof(_Tp) == 1) {
return 1 << 8;
}
@@ -214,14 +213,13 @@ _LIBCPP_HIDE_FROM_ABI constexpr unsigned __radix_sort_min_bound() {
template <class _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr unsigned __radix_sort_max_bound() {
- static_assert(is_arithmetic<_Tp>::value);
+ static_assert(is_integral_v<_Tp > || numeric_limits<_Tp>::is_iec559);
if constexpr (sizeof(_Tp) >= 8) {
return 1 << 15;
}
return 1 << 16;
}
-
#endif // _LIBCPP_STD_VER >= 17
template <class _AlgPolicy, class _Compare, class _RandomAccessIterator>
>From a358b1895d94354b474267b81613ba8b3c2351ce Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=94=D0=BC=D0=B8=D1=82=D1=80=D0=B8=D0=B9=20=D0=98=D0=B7?=
=?UTF-8?q?=D0=B2=D0=BE=D0=BB=D0=BE=D0=B2?= <dmitriy at izvolov.ru>
Date: Tue, 25 Mar 2025 18:31:06 +0300
Subject: [PATCH 10/12] metafunc
---
libcxx/include/__algorithm/radix_sort.h | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/libcxx/include/__algorithm/radix_sort.h b/libcxx/include/__algorithm/radix_sort.h
index 995b1fea7a6bb..49fdb34f0d68a 100644
--- a/libcxx/include/__algorithm/radix_sort.h
+++ b/libcxx/include/__algorithm/radix_sort.h
@@ -302,7 +302,7 @@ _LIBCPP_HIDE_FROM_ABI constexpr auto __shift_to_unsigned(_Ip __n) {
}
template <size_t _Size>
-struct __unsigned_integer_of_size {};
+struct __unsigned_integer_of_size;
template <>
struct __unsigned_integer_of_size<1> {
@@ -324,12 +324,12 @@ struct __unsigned_integer_of_size<8> {
using type = uint64_t;
};
+# if _LIBCPP_HAS_INT128
template <>
struct __unsigned_integer_of_size<16> {
-# if _LIBCPP_HAS_INT128
using type = __int128;
-# endif
};
+# endif
template <size_t _Size>
using __unsigned_integer_of_size_t _LIBCPP_NODEBUG = typename __unsigned_integer_of_size<_Size>::type;
>From c6918e06b709544e8e9dfe842ef299821a883548 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=94=D0=BC=D0=B8=D1=82=D1=80=D0=B8=D0=B9=20=D0=98=D0=B7?=
=?UTF-8?q?=D0=B2=D0=BE=D0=BB=D0=BE=D0=B2?= <dmitriy at izvolov.ru>
Date: Tue, 25 Mar 2025 18:31:26 +0300
Subject: [PATCH 11/12] test-for-long-double
---
.../alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp | 1 +
1 file changed, 1 insertion(+)
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp
index 7691b2c5874ea..e05457492db32 100644
--- a/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp
@@ -250,6 +250,7 @@ int main(int, char**) {
test<int>();
test_floating<float>();
test_floating<double>();
+ test_floating<long double>();
test_enum();
#if TEST_STD_VER >= 26
static_assert(test<int>());
>From 21b7b23b3945a42790b350cd84f097c3c4714a80 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=94=D0=BC=D0=B8=D1=82=D1=80=D0=B8=D0=B9=20=D0=98=D0=B7?=
=?UTF-8?q?=D0=B2=D0=BE=D0=BB=D0=BE=D0=B2?= <dmitriy at izvolov.ru>
Date: Tue, 25 Mar 2025 21:38:30 +0300
Subject: [PATCH 12/12] test
---
libcxx/include/__algorithm/stable_sort.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libcxx/include/__algorithm/stable_sort.h b/libcxx/include/__algorithm/stable_sort.h
index 4c69eb78bd683..5852800e0b180 100644
--- a/libcxx/include/__algorithm/stable_sort.h
+++ b/libcxx/include/__algorithm/stable_sort.h
@@ -249,7 +249,7 @@ _LIBCPP_CONSTEXPR_SINCE_CXX26 void __stable_sort(
#if _LIBCPP_STD_VER >= 17
constexpr auto __default_comp = __desugars_to_v<__less_tag, __remove_cvref_t<_Compare>, value_type, value_type >;
constexpr auto __arithmetic_value =
- (is_integral_v<value_type > || numeric_limits<value_type>::is_iec559) &&
+ (is_integral_v<value_type >/* || numeric_limits<value_type>::is_iec559*/) &&
is_same_v< value_type&, __iter_reference<_RandomAccessIterator>>;
if constexpr (__default_comp && __arithmetic_value) {
if (__len <= __buff_size && __len >= static_cast<difference_type>(std::__radix_sort_min_bound<value_type>()) &&
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