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llvm-project/libcxx/include/__algorithm/sort.h
Louis Dionne c54c90da4f [libc++][NFC] Fix typo in comment
2023-03-17 11:57:34 -04:00

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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___ALGORITHM_SORT_H
#define _LIBCPP___ALGORITHM_SORT_H
#include <__algorithm/comp.h>
#include <__algorithm/comp_ref_type.h>
#include <__algorithm/iter_swap.h>
#include <__algorithm/iterator_operations.h>
#include <__algorithm/min_element.h>
#include <__algorithm/partial_sort.h>
#include <__algorithm/unwrap_iter.h>
#include <__assert>
#include <__bit/blsr.h>
#include <__bit/countl.h>
#include <__bit/countr.h>
#include <__config>
#include <__debug>
#include <__debug_utils/randomize_range.h>
#include <__functional/operations.h>
#include <__functional/ranges_operations.h>
#include <__iterator/iterator_traits.h>
#include <__memory/destruct_n.h>
#include <__memory/unique_ptr.h>
#include <__type_traits/conditional.h>
#include <__type_traits/disjunction.h>
#include <__type_traits/is_arithmetic.h>
#include <__utility/move.h>
#include <__utility/pair.h>
#include <climits>
#include <cstdint>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
// stable, 2-3 compares, 0-2 swaps
template <class _AlgPolicy, class _Compare, class _ForwardIterator>
_LIBCPP_HIDE_FROM_ABI
_LIBCPP_CONSTEXPR_SINCE_CXX14 unsigned __sort3(_ForwardIterator __x, _ForwardIterator __y, _ForwardIterator __z,
_Compare __c) {
using _Ops = _IterOps<_AlgPolicy>;
unsigned __r = 0;
if (!__c(*__y, *__x)) // if x <= y
{
if (!__c(*__z, *__y)) // if y <= z
return __r; // x <= y && y <= z
// x <= y && y > z
_Ops::iter_swap(__y, __z); // x <= z && y < z
__r = 1;
if (__c(*__y, *__x)) // if x > y
{
_Ops::iter_swap(__x, __y); // x < y && y <= z
__r = 2;
}
return __r; // x <= y && y < z
}
if (__c(*__z, *__y)) // x > y, if y > z
{
_Ops::iter_swap(__x, __z); // x < y && y < z
__r = 1;
return __r;
}
_Ops::iter_swap(__x, __y); // x > y && y <= z
__r = 1; // x < y && x <= z
if (__c(*__z, *__y)) // if y > z
{
_Ops::iter_swap(__y, __z); // x <= y && y < z
__r = 2;
}
return __r;
} // x <= y && y <= z
// stable, 3-6 compares, 0-5 swaps
template <class _AlgPolicy, class _Compare, class _ForwardIterator>
_LIBCPP_HIDE_FROM_ABI
void __sort4(_ForwardIterator __x1, _ForwardIterator __x2, _ForwardIterator __x3, _ForwardIterator __x4,
_Compare __c) {
using _Ops = _IterOps<_AlgPolicy>;
std::__sort3<_AlgPolicy, _Compare>(__x1, __x2, __x3, __c);
if (__c(*__x4, *__x3)) {
_Ops::iter_swap(__x3, __x4);
if (__c(*__x3, *__x2)) {
_Ops::iter_swap(__x2, __x3);
if (__c(*__x2, *__x1)) {
_Ops::iter_swap(__x1, __x2);
}
}
}
}
// stable, 4-10 compares, 0-9 swaps
template <class _AlgPolicy, class _Comp, class _ForwardIterator>
_LIBCPP_HIDE_FROM_ABI void __sort5(_ForwardIterator __x1, _ForwardIterator __x2, _ForwardIterator __x3,
_ForwardIterator __x4, _ForwardIterator __x5, _Comp __comp) {
using _Ops = _IterOps<_AlgPolicy>;
std::__sort4<_AlgPolicy, _Comp>(__x1, __x2, __x3, __x4, __comp);
if (__comp(*__x5, *__x4)) {
_Ops::iter_swap(__x4, __x5);
if (__comp(*__x4, *__x3)) {
_Ops::iter_swap(__x3, __x4);
if (__comp(*__x3, *__x2)) {
_Ops::iter_swap(__x2, __x3);
if (__comp(*__x2, *__x1)) {
_Ops::iter_swap(__x1, __x2);
}
}
}
}
}
// The comparator being simple is a prerequisite for using the branchless optimization.
template <class _Tp>
struct __is_simple_comparator : false_type {};
template <class _Tp>
struct __is_simple_comparator<__less<_Tp>&> : true_type {};
template <class _Tp>
struct __is_simple_comparator<less<_Tp>&> : true_type {};
template <class _Tp>
struct __is_simple_comparator<greater<_Tp>&> : true_type {};
#if _LIBCPP_STD_VER >= 20
template <>
struct __is_simple_comparator<ranges::less&> : true_type {};
template <>
struct __is_simple_comparator<ranges::greater&> : true_type {};
#endif
template <class _Compare, class _Iter, class _Tp = typename iterator_traits<_Iter>::value_type>
using __use_branchless_sort =
integral_constant<bool, __is_cpp17_contiguous_iterator<_Iter>::value && sizeof(_Tp) <= sizeof(void*) &&
is_arithmetic<_Tp>::value && __is_simple_comparator<_Compare>::value>;
namespace __detail {
// Size in bits for the bitset in use.
enum { __block_size = sizeof(uint64_t) * 8 };
} // namespace __detail
// Ensures that __c(*__x, *__y) is true by swapping *__x and *__y if necessary.
template <class _Compare, class _RandomAccessIterator>
inline _LIBCPP_HIDE_FROM_ABI void __cond_swap(_RandomAccessIterator __x, _RandomAccessIterator __y, _Compare __c) {
// Note: this function behaves correctly even with proxy iterators (because it relies on `value_type`).
using value_type = typename iterator_traits<_RandomAccessIterator>::value_type;
bool __r = __c(*__x, *__y);
value_type __tmp = __r ? *__x : *__y;
*__y = __r ? *__y : *__x;
*__x = __tmp;
}
// Ensures that *__x, *__y and *__z are ordered according to the comparator __c,
// under the assumption that *__y and *__z are already ordered.
template <class _Compare, class _RandomAccessIterator>
inline _LIBCPP_HIDE_FROM_ABI void __partially_sorted_swap(_RandomAccessIterator __x, _RandomAccessIterator __y,
_RandomAccessIterator __z, _Compare __c) {
// Note: this function behaves correctly even with proxy iterators (because it relies on `value_type`).
using value_type = typename iterator_traits<_RandomAccessIterator>::value_type;
bool __r = __c(*__z, *__x);
value_type __tmp = __r ? *__z : *__x;
*__z = __r ? *__x : *__z;
__r = __c(__tmp, *__y);
*__x = __r ? *__x : *__y;
*__y = __r ? *__y : __tmp;
}
template <class, class _Compare, class _RandomAccessIterator>
inline _LIBCPP_HIDE_FROM_ABI __enable_if_t<__use_branchless_sort<_Compare, _RandomAccessIterator>::value, void>
__sort3_maybe_branchless(_RandomAccessIterator __x1, _RandomAccessIterator __x2, _RandomAccessIterator __x3,
_Compare __c) {
std::__cond_swap<_Compare>(__x2, __x3, __c);
std::__partially_sorted_swap<_Compare>(__x1, __x2, __x3, __c);
}
template <class _AlgPolicy, class _Compare, class _RandomAccessIterator>
inline _LIBCPP_HIDE_FROM_ABI __enable_if_t<!__use_branchless_sort<_Compare, _RandomAccessIterator>::value, void>
__sort3_maybe_branchless(_RandomAccessIterator __x1, _RandomAccessIterator __x2, _RandomAccessIterator __x3,
_Compare __c) {
std::__sort3<_AlgPolicy, _Compare>(__x1, __x2, __x3, __c);
}
template <class, class _Compare, class _RandomAccessIterator>
inline _LIBCPP_HIDE_FROM_ABI __enable_if_t<__use_branchless_sort<_Compare, _RandomAccessIterator>::value, void>
__sort4_maybe_branchless(_RandomAccessIterator __x1, _RandomAccessIterator __x2, _RandomAccessIterator __x3,
_RandomAccessIterator __x4, _Compare __c) {
std::__cond_swap<_Compare>(__x1, __x3, __c);
std::__cond_swap<_Compare>(__x2, __x4, __c);
std::__cond_swap<_Compare>(__x1, __x2, __c);
std::__cond_swap<_Compare>(__x3, __x4, __c);
std::__cond_swap<_Compare>(__x2, __x3, __c);
}
template <class _AlgPolicy, class _Compare, class _RandomAccessIterator>
inline _LIBCPP_HIDE_FROM_ABI __enable_if_t<!__use_branchless_sort<_Compare, _RandomAccessIterator>::value, void>
__sort4_maybe_branchless(_RandomAccessIterator __x1, _RandomAccessIterator __x2, _RandomAccessIterator __x3,
_RandomAccessIterator __x4, _Compare __c) {
std::__sort4<_AlgPolicy, _Compare>(__x1, __x2, __x3, __x4, __c);
}
template <class _AlgPolicy, class _Compare, class _RandomAccessIterator>
inline _LIBCPP_HIDE_FROM_ABI __enable_if_t<__use_branchless_sort<_Compare, _RandomAccessIterator>::value, void>
__sort5_maybe_branchless(
_RandomAccessIterator __x1,
_RandomAccessIterator __x2,
_RandomAccessIterator __x3,
_RandomAccessIterator __x4,
_RandomAccessIterator __x5,
_Compare __c) {
std::__cond_swap<_Compare>(__x1, __x2, __c);
std::__cond_swap<_Compare>(__x4, __x5, __c);
std::__partially_sorted_swap<_Compare>(__x3, __x4, __x5, __c);
std::__cond_swap<_Compare>(__x2, __x5, __c);
std::__partially_sorted_swap<_Compare>(__x1, __x3, __x4, __c);
std::__partially_sorted_swap<_Compare>(__x2, __x3, __x4, __c);
}
template <class _AlgPolicy, class _Compare, class _RandomAccessIterator>
inline _LIBCPP_HIDE_FROM_ABI __enable_if_t<!__use_branchless_sort<_Compare, _RandomAccessIterator>::value, void>
__sort5_maybe_branchless(_RandomAccessIterator __x1, _RandomAccessIterator __x2, _RandomAccessIterator __x3,
_RandomAccessIterator __x4, _RandomAccessIterator __x5, _Compare __c) {
std::__sort5<_AlgPolicy, _Compare, _RandomAccessIterator>(
std::move(__x1), std::move(__x2), std::move(__x3), std::move(__x4), std::move(__x5), __c);
}
// Assumes size > 0
template <class _AlgPolicy, class _Compare, class _BidirectionalIterator>
_LIBCPP_HIDE_FROM_ABI
_LIBCPP_CONSTEXPR_SINCE_CXX14 void __selection_sort(_BidirectionalIterator __first, _BidirectionalIterator __last,
_Compare __comp) {
_BidirectionalIterator __lm1 = __last;
for (--__lm1; __first != __lm1; ++__first) {
_BidirectionalIterator __i = std::__min_element<_Compare>(__first, __last, __comp);
if (__i != __first)
_IterOps<_AlgPolicy>::iter_swap(__first, __i);
}
}
// Sort the iterator range [__first, __last) using the comparator __comp using
// the insertion sort algorithm.
template <class _AlgPolicy, class _Compare, class _BidirectionalIterator>
_LIBCPP_HIDE_FROM_ABI
void __insertion_sort(_BidirectionalIterator __first, _BidirectionalIterator __last, _Compare __comp) {
using _Ops = _IterOps<_AlgPolicy>;
typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
if (__first == __last)
return;
_BidirectionalIterator __i = __first;
for (++__i; __i != __last; ++__i) {
_BidirectionalIterator __j = __i;
--__j;
if (__comp(*__i, *__j)) {
value_type __t(_Ops::__iter_move(__i));
_BidirectionalIterator __k = __j;
__j = __i;
do {
*__j = _Ops::__iter_move(__k);
__j = __k;
} while (__j != __first && __comp(__t, *--__k));
*__j = std::move(__t);
}
}
}
// Sort the iterator range [__first, __last) using the comparator __comp using
// the insertion sort algorithm. Insertion sort has two loops, outer and inner.
// The implementation below has no bounds check (unguarded) for the inner loop.
// Assumes that there is an element in the position (__first - 1) and that each
// element in the input range is greater or equal to the element at __first - 1.
template <class _AlgPolicy, class _Compare, class _RandomAccessIterator>
_LIBCPP_HIDE_FROM_ABI void
__insertion_sort_unguarded(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp) {
using _Ops = _IterOps<_AlgPolicy>;
typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
if (__first == __last)
return;
for (_RandomAccessIterator __i = __first + difference_type(1); __i != __last; ++__i) {
_RandomAccessIterator __j = __i - difference_type(1);
if (__comp(*__i, *__j)) {
value_type __t(_Ops::__iter_move(__i));
_RandomAccessIterator __k = __j;
__j = __i;
do {
*__j = _Ops::__iter_move(__k);
__j = __k;
} while (__comp(__t, *--__k)); // No need for bounds check due to the assumption stated above.
*__j = std::move(__t);
}
}
}
template <class _AlgPolicy, class _Comp, class _RandomAccessIterator>
_LIBCPP_HIDE_FROM_ABI bool __insertion_sort_incomplete(
_RandomAccessIterator __first, _RandomAccessIterator __last, _Comp __comp) {
using _Ops = _IterOps<_AlgPolicy>;
typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
switch (__last - __first) {
case 0:
case 1:
return true;
case 2:
if (__comp(*--__last, *__first))
_Ops::iter_swap(__first, __last);
return true;
case 3:
std::__sort3_maybe_branchless<_AlgPolicy, _Comp>(__first, __first + difference_type(1), --__last, __comp);
return true;
case 4:
std::__sort4_maybe_branchless<_AlgPolicy, _Comp>(
__first, __first + difference_type(1), __first + difference_type(2), --__last, __comp);
return true;
case 5:
std::__sort5_maybe_branchless<_AlgPolicy, _Comp>(
__first, __first + difference_type(1), __first + difference_type(2), __first + difference_type(3),
--__last, __comp);
return true;
}
typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
_RandomAccessIterator __j = __first + difference_type(2);
std::__sort3_maybe_branchless<_AlgPolicy, _Comp>(__first, __first + difference_type(1), __j, __comp);
const unsigned __limit = 8;
unsigned __count = 0;
for (_RandomAccessIterator __i = __j + difference_type(1); __i != __last; ++__i) {
if (__comp(*__i, *__j)) {
value_type __t(_Ops::__iter_move(__i));
_RandomAccessIterator __k = __j;
__j = __i;
do {
*__j = _Ops::__iter_move(__k);
__j = __k;
} while (__j != __first && __comp(__t, *--__k));
*__j = std::move(__t);
if (++__count == __limit)
return ++__i == __last;
}
__j = __i;
}
return true;
}
template <class _AlgPolicy, class _Compare, class _BidirectionalIterator>
_LIBCPP_HIDE_FROM_ABI
void __insertion_sort_move(_BidirectionalIterator __first1, _BidirectionalIterator __last1,
typename iterator_traits<_BidirectionalIterator>::value_type* __first2, _Compare __comp) {
using _Ops = _IterOps<_AlgPolicy>;
typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
if (__first1 != __last1) {
__destruct_n __d(0);
unique_ptr<value_type, __destruct_n&> __h(__first2, __d);
value_type* __last2 = __first2;
::new ((void*)__last2) value_type(_Ops::__iter_move(__first1));
__d.template __incr<value_type>();
for (++__last2; ++__first1 != __last1; ++__last2) {
value_type* __j2 = __last2;
value_type* __i2 = __j2;
if (__comp(*__first1, *--__i2)) {
::new ((void*)__j2) value_type(std::move(*__i2));
__d.template __incr<value_type>();
for (--__j2; __i2 != __first2 && __comp(*__first1, *--__i2); --__j2)
*__j2 = std::move(*__i2);
*__j2 = _Ops::__iter_move(__first1);
} else {
::new ((void*)__j2) value_type(_Ops::__iter_move(__first1));
__d.template __incr<value_type>();
}
}
__h.release();
}
}
template <class _AlgPolicy, class _RandomAccessIterator>
inline _LIBCPP_HIDE_FROM_ABI void __swap_bitmap_pos(
_RandomAccessIterator __first, _RandomAccessIterator __last, uint64_t& __left_bitset, uint64_t& __right_bitset) {
using _Ops = _IterOps<_AlgPolicy>;
typedef typename std::iterator_traits<_RandomAccessIterator>::difference_type difference_type;
// Swap one pair on each iteration as long as both bitsets have at least one
// element for swapping.
while (__left_bitset != 0 && __right_bitset != 0) {
difference_type __tz_left = __libcpp_ctz(__left_bitset);
__left_bitset = __libcpp_blsr(__left_bitset);
difference_type __tz_right = __libcpp_ctz(__right_bitset);
__right_bitset = __libcpp_blsr(__right_bitset);
_Ops::iter_swap(__first + __tz_left, __last - __tz_right);
}
}
template <class _Compare,
class _RandomAccessIterator,
class _ValueType = typename iterator_traits<_RandomAccessIterator>::value_type>
inline _LIBCPP_HIDE_FROM_ABI void
__populate_left_bitset(_RandomAccessIterator __first, _Compare __comp, _ValueType& __pivot, uint64_t& __left_bitset) {
// Possible vectorization. With a proper "-march" flag, the following loop
// will be compiled into a set of SIMD instructions.
_RandomAccessIterator __iter = __first;
for (int __j = 0; __j < __detail::__block_size;) {
bool __comp_result = !__comp(*__iter, __pivot);
__left_bitset |= (static_cast<uint64_t>(__comp_result) << __j);
__j++;
++__iter;
}
}
template <class _Compare,
class _RandomAccessIterator,
class _ValueType = typename iterator_traits<_RandomAccessIterator>::value_type>
inline _LIBCPP_HIDE_FROM_ABI void
__populate_right_bitset(_RandomAccessIterator __lm1, _Compare __comp, _ValueType& __pivot, uint64_t& __right_bitset) {
// Possible vectorization. With a proper "-march" flag, the following loop
// will be compiled into a set of SIMD instructions.
_RandomAccessIterator __iter = __lm1;
for (int __j = 0; __j < __detail::__block_size;) {
bool __comp_result = __comp(*__iter, __pivot);
__right_bitset |= (static_cast<uint64_t>(__comp_result) << __j);
__j++;
--__iter;
}
}
template <class _AlgPolicy,
class _Compare,
class _RandomAccessIterator,
class _ValueType = typename iterator_traits<_RandomAccessIterator>::value_type>
inline _LIBCPP_HIDE_FROM_ABI void __bitset_partition_partial_blocks(
_RandomAccessIterator& __first,
_RandomAccessIterator& __lm1,
_Compare __comp,
_ValueType& __pivot,
uint64_t& __left_bitset,
uint64_t& __right_bitset) {
typedef typename std::iterator_traits<_RandomAccessIterator>::difference_type difference_type;
difference_type __remaining_len = __lm1 - __first + 1;
difference_type __l_size;
difference_type __r_size;
if (__left_bitset == 0 && __right_bitset == 0) {
__l_size = __remaining_len / 2;
__r_size = __remaining_len - __l_size;
} else if (__left_bitset == 0) {
// We know at least one side is a full block.
__l_size = __remaining_len - __detail::__block_size;
__r_size = __detail::__block_size;
} else { // if (__right_bitset == 0)
__l_size = __detail::__block_size;
__r_size = __remaining_len - __detail::__block_size;
}
// Record the comparison outcomes for the elements currently on the left side.
if (__left_bitset == 0) {
_RandomAccessIterator __iter = __first;
for (int __j = 0; __j < __l_size; __j++) {
bool __comp_result = !__comp(*__iter, __pivot);
__left_bitset |= (static_cast<uint64_t>(__comp_result) << __j);
++__iter;
}
}
// Record the comparison outcomes for the elements currently on the right
// side.
if (__right_bitset == 0) {
_RandomAccessIterator __iter = __lm1;
for (int __j = 0; __j < __r_size; __j++) {
bool __comp_result = __comp(*__iter, __pivot);
__right_bitset |= (static_cast<uint64_t>(__comp_result) << __j);
--__iter;
}
}
std::__swap_bitmap_pos<_AlgPolicy, _RandomAccessIterator>(__first, __lm1, __left_bitset, __right_bitset);
__first += (__left_bitset == 0) ? __l_size : 0;
__lm1 -= (__right_bitset == 0) ? __r_size : 0;
}
template <class _AlgPolicy, class _RandomAccessIterator>
inline _LIBCPP_HIDE_FROM_ABI void __swap_bitmap_pos_within(
_RandomAccessIterator& __first, _RandomAccessIterator& __lm1, uint64_t& __left_bitset, uint64_t& __right_bitset) {
using _Ops = _IterOps<_AlgPolicy>;
typedef typename std::iterator_traits<_RandomAccessIterator>::difference_type difference_type;
if (__left_bitset) {
// Swap within the left side. Need to find set positions in the reverse
// order.
while (__left_bitset != 0) {
difference_type __tz_left = __detail::__block_size - 1 - __libcpp_clz(__left_bitset);
__left_bitset &= (static_cast<uint64_t>(1) << __tz_left) - 1;
_RandomAccessIterator __it = __first + __tz_left;
if (__it != __lm1) {
_Ops::iter_swap(__it, __lm1);
}
--__lm1;
}
__first = __lm1 + difference_type(1);
} else if (__right_bitset) {
// Swap within the right side. Need to find set positions in the reverse
// order.
while (__right_bitset != 0) {
difference_type __tz_right = __detail::__block_size - 1 - __libcpp_clz(__right_bitset);
__right_bitset &= (static_cast<uint64_t>(1) << __tz_right) - 1;
_RandomAccessIterator __it = __lm1 - __tz_right;
if (__it != __first) {
_Ops::iter_swap(__it, __first);
}
++__first;
}
}
}
// Partition [__first, __last) using the comparator __comp. *__first has the
// chosen pivot. Elements that are equivalent are kept to the left of the
// pivot. Returns the iterator for the pivot and a bool value which is true if
// the provided range is already sorted, false otherwise. We assume that the
// length of the range is at least three elements.
//
// __bitset_partition uses bitsets for storing outcomes of the comparisons
// between the pivot and other elements.
template <class _AlgPolicy, class _RandomAccessIterator, class _Compare>
_LIBCPP_HIDE_FROM_ABI std::pair<_RandomAccessIterator, bool>
__bitset_partition(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp) {
using _Ops = _IterOps<_AlgPolicy>;
typedef typename std::iterator_traits<_RandomAccessIterator>::value_type value_type;
typedef typename std::iterator_traits<_RandomAccessIterator>::difference_type difference_type;
_LIBCPP_ASSERT(__last - __first >= difference_type(3), "");
_RandomAccessIterator __begin = __first;
value_type __pivot(_Ops::__iter_move(__first));
// Find the first element greater than the pivot.
if (__comp(__pivot, *(__last - difference_type(1)))) {
// Not guarded since we know the last element is greater than the pivot.
while (!__comp(__pivot, *++__first)) {
}
} else {
while (++__first < __last && !__comp(__pivot, *__first)) {
}
}
// Find the last element less than or equal to the pivot.
if (__first < __last) {
// It will be always guarded because __introsort will do the median-of-three
// before calling this.
while (__comp(__pivot, *--__last)) {
}
}
// If the first element greater than the pivot is at or after the
// last element less than or equal to the pivot, then we have covered the
// entire range without swapping elements. This implies the range is already
// partitioned.
bool __already_partitioned = __first >= __last;
if (!__already_partitioned) {
_Ops::iter_swap(__first, __last);
++__first;
}
// In [__first, __last) __last is not inclusive. From now on, it uses last
// minus one to be inclusive on both sides.
_RandomAccessIterator __lm1 = __last - difference_type(1);
uint64_t __left_bitset = 0;
uint64_t __right_bitset = 0;
// Reminder: length = __lm1 - __first + 1.
while (__lm1 - __first >= 2 * __detail::__block_size - 1) {
// Record the comparison outcomes for the elements currently on the left
// side.
if (__left_bitset == 0)
std::__populate_left_bitset<_Compare>(__first, __comp, __pivot, __left_bitset);
// Record the comparison outcomes for the elements currently on the right
// side.
if (__right_bitset == 0)
std::__populate_right_bitset<_Compare>(__lm1, __comp, __pivot, __right_bitset);
// Swap the elements recorded to be the candidates for swapping in the
// bitsets.
std::__swap_bitmap_pos<_AlgPolicy, _RandomAccessIterator>(__first, __lm1, __left_bitset, __right_bitset);
// Only advance the iterator if all the elements that need to be moved to
// other side were moved.
__first += (__left_bitset == 0) ? difference_type(__detail::__block_size) : difference_type(0);
__lm1 -= (__right_bitset == 0) ? difference_type(__detail::__block_size) : difference_type(0);
}
// Now, we have a less-than a block worth of elements on at least one of the
// sides.
std::__bitset_partition_partial_blocks<_AlgPolicy, _Compare>(
__first, __lm1, __comp, __pivot, __left_bitset, __right_bitset);
// At least one the bitsets would be empty. For the non-empty one, we need to
// properly partition the elements that appear within that bitset.
std::__swap_bitmap_pos_within<_AlgPolicy>(__first, __lm1, __left_bitset, __right_bitset);
// Move the pivot to its correct position.
_RandomAccessIterator __pivot_pos = __first - difference_type(1);
if (__begin != __pivot_pos) {
*__begin = _Ops::__iter_move(__pivot_pos);
}
*__pivot_pos = std::move(__pivot);
return std::make_pair(__pivot_pos, __already_partitioned);
}
// Partition [__first, __last) using the comparator __comp. *__first has the
// chosen pivot. Elements that are equivalent are kept to the right of the
// pivot. Returns the iterator for the pivot and a bool value which is true if
// the provided range is already sorted, false otherwise. We assume that the
// length of the range is at least three elements.
template <class _AlgPolicy, class _RandomAccessIterator, class _Compare>
_LIBCPP_HIDE_FROM_ABI std::pair<_RandomAccessIterator, bool>
__partition_with_equals_on_right(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp) {
using _Ops = _IterOps<_AlgPolicy>;
typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
typedef typename std::iterator_traits<_RandomAccessIterator>::value_type value_type;
_LIBCPP_ASSERT(__last - __first >= difference_type(3), "");
_RandomAccessIterator __begin = __first;
value_type __pivot(_Ops::__iter_move(__first));
// Find the first element greater or equal to the pivot. It will be always
// guarded because __introsort will do the median-of-three before calling
// this.
while (__comp(*++__first, __pivot))
;
// Find the last element less than the pivot.
if (__begin == __first - difference_type(1)) {
while (__first < __last && !__comp(*--__last, __pivot))
;
} else {
// Guarded.
while (!__comp(*--__last, __pivot))
;
}
// If the first element greater than or equal to the pivot is at or after the
// last element less than the pivot, then we have covered the entire range
// without swapping elements. This implies the range is already partitioned.
bool __already_partitioned = __first >= __last;
// Go through the remaining elements. Swap pairs of elements (one to the
// right of the pivot and the other to left of the pivot) that are not on the
// correct side of the pivot.
while (__first < __last) {
_Ops::iter_swap(__first, __last);
while (__comp(*++__first, __pivot))
;
while (!__comp(*--__last, __pivot))
;
}
// Move the pivot to its correct position.
_RandomAccessIterator __pivot_pos = __first - difference_type(1);
if (__begin != __pivot_pos) {
*__begin = _Ops::__iter_move(__pivot_pos);
}
*__pivot_pos = std::move(__pivot);
return std::make_pair(__pivot_pos, __already_partitioned);
}
// Similar to the above function. Elements equivalent to the pivot are put to
// the left of the pivot. Returns the iterator to the pivot element.
template <class _AlgPolicy, class _RandomAccessIterator, class _Compare>
_LIBCPP_HIDE_FROM_ABI _RandomAccessIterator
__partition_with_equals_on_left(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp) {
using _Ops = _IterOps<_AlgPolicy>;
typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
typedef typename std::iterator_traits<_RandomAccessIterator>::value_type value_type;
_RandomAccessIterator __begin = __first;
value_type __pivot(_Ops::__iter_move(__first));
if (__comp(__pivot, *(__last - difference_type(1)))) {
// Guarded.
while (!__comp(__pivot, *++__first)) {
}
} else {
while (++__first < __last && !__comp(__pivot, *__first)) {
}
}
if (__first < __last) {
// It will be always guarded because __introsort will do the
// median-of-three before calling this.
while (__comp(__pivot, *--__last)) {
}
}
while (__first < __last) {
_Ops::iter_swap(__first, __last);
while (!__comp(__pivot, *++__first))
;
while (__comp(__pivot, *--__last))
;
}
_RandomAccessIterator __pivot_pos = __first - difference_type(1);
if (__begin != __pivot_pos) {
*__begin = _Ops::__iter_move(__pivot_pos);
}
*__pivot_pos = std::move(__pivot);
return __first;
}
// The main sorting function. Implements introsort combined with other ideas:
// - option of using block quick sort for partitioning,
// - guarded and unguarded insertion sort for small lengths,
// - Tuckey's ninther technique for computing the pivot,
// - check on whether partition was not required.
// The implementation is partly based on Orson Peters' pattern-defeating
// quicksort, published at: <https://github.com/orlp/pdqsort>.
template <class _AlgPolicy, class _Compare, class _RandomAccessIterator, bool _UseBitSetPartition>
void __introsort(_RandomAccessIterator __first,
_RandomAccessIterator __last,
_Compare __comp,
typename iterator_traits<_RandomAccessIterator>::difference_type __depth,
bool __leftmost = true) {
using _Ops = _IterOps<_AlgPolicy>;
typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
using _Comp_ref = __comp_ref_type<_Compare>;
// Upper bound for using insertion sort for sorting.
_LIBCPP_CONSTEXPR difference_type __limit = 24;
// Lower bound for using Tuckey's ninther technique for median computation.
_LIBCPP_CONSTEXPR difference_type __ninther_threshold = 128;
while (true) {
difference_type __len = __last - __first;
switch (__len) {
case 0:
case 1:
return;
case 2:
if (__comp(*--__last, *__first))
_Ops::iter_swap(__first, __last);
return;
case 3:
std::__sort3_maybe_branchless<_AlgPolicy, _Compare>(__first, __first + difference_type(1), --__last, __comp);
return;
case 4:
std::__sort4_maybe_branchless<_AlgPolicy, _Compare>(
__first, __first + difference_type(1), __first + difference_type(2), --__last, __comp);
return;
case 5:
std::__sort5_maybe_branchless<_AlgPolicy, _Compare>(
__first, __first + difference_type(1), __first + difference_type(2), __first + difference_type(3),
--__last, __comp);
return;
}
// Use insertion sort if the length of the range is below the specified limit.
if (__len < __limit) {
if (__leftmost) {
std::__insertion_sort<_AlgPolicy, _Compare>(__first, __last, __comp);
} else {
std::__insertion_sort_unguarded<_AlgPolicy, _Compare>(__first, __last, __comp);
}
return;
}
if (__depth == 0) {
// Fallback to heap sort as Introsort suggests.
std::__partial_sort<_AlgPolicy, _Compare>(__first, __last, __last, __comp);
return;
}
--__depth;
{
difference_type __half_len = __len / 2;
// Use Tuckey's ninther technique or median of 3 for pivot selection
// depending on the length of the range being sorted.
if (__len > __ninther_threshold) {
std::__sort3<_AlgPolicy, _Compare>(__first, __first + __half_len, __last - difference_type(1), __comp);
std::__sort3<_AlgPolicy, _Compare>(
__first + difference_type(1), __first + (__half_len - 1), __last - difference_type(2), __comp);
std::__sort3<_AlgPolicy, _Compare>(
__first + difference_type(2), __first + (__half_len + 1), __last - difference_type(3), __comp);
std::__sort3<_AlgPolicy, _Compare>(
__first + (__half_len - 1), __first + __half_len, __first + (__half_len + 1), __comp);
_Ops::iter_swap(__first, __first + __half_len);
} else {
std::__sort3<_AlgPolicy, _Compare>(__first + __half_len, __first, __last - difference_type(1), __comp);
}
}
// The elements to the left of the current iterator range are already
// sorted. If the current iterator range to be sorted is not the
// leftmost part of the entire iterator range and the pivot is same as
// the highest element in the range to the left, then we know that all
// the elements in the range [first, pivot] would be equal to the pivot,
// assuming the equal elements are put on the left side when
// partitioned. This also means that we do not need to sort the left
// side of the partition.
if (!__leftmost && !__comp(*(__first - difference_type(1)), *__first)) {
__first = std::__partition_with_equals_on_left<_AlgPolicy, _RandomAccessIterator, _Comp_ref>(
__first, __last, _Comp_ref(__comp));
continue;
}
// Use bitset partition only if asked for.
auto __ret =
_UseBitSetPartition
? std::__bitset_partition<_AlgPolicy, _RandomAccessIterator, _Compare>(__first, __last, __comp)
: std::__partition_with_equals_on_right<_AlgPolicy, _RandomAccessIterator, _Compare>(__first, __last, __comp);
_RandomAccessIterator __i = __ret.first;
// [__first, __i) < *__i and *__i <= [__i+1, __last)
// If we were given a perfect partition, see if insertion sort is quick...
if (__ret.second) {
bool __fs = std::__insertion_sort_incomplete<_AlgPolicy, _Compare>(__first, __i, __comp);
if (std::__insertion_sort_incomplete<_AlgPolicy, _Compare>(__i + difference_type(1), __last, __comp)) {
if (__fs)
return;
__last = __i;
continue;
} else {
if (__fs) {
__first = ++__i;
continue;
}
}
}
// Sort the left partiton recursively and the right partition with tail recursion elimination.
std::__introsort<_AlgPolicy, _Compare, _RandomAccessIterator, _UseBitSetPartition>(
__first, __i, __comp, __depth, __leftmost);
__leftmost = false;
__first = ++__i;
}
}
template <typename _Number>
inline _LIBCPP_HIDE_FROM_ABI _Number __log2i(_Number __n) {
if (__n == 0)
return 0;
if (sizeof(__n) <= sizeof(unsigned))
return sizeof(unsigned) * CHAR_BIT - 1 - __libcpp_clz(static_cast<unsigned>(__n));
if (sizeof(__n) <= sizeof(unsigned long))
return sizeof(unsigned long) * CHAR_BIT - 1 - __libcpp_clz(static_cast<unsigned long>(__n));
if (sizeof(__n) <= sizeof(unsigned long long))
return sizeof(unsigned long long) * CHAR_BIT - 1 - __libcpp_clz(static_cast<unsigned long long>(__n));
_Number __log2 = 0;
while (__n > 1) {
__log2++;
__n >>= 1;
}
return __log2;
}
template <class _Comp, class _RandomAccessIterator>
void __sort(_RandomAccessIterator, _RandomAccessIterator, _Comp);
extern template _LIBCPP_FUNC_VIS void __sort<__less<char>&, char*>(char*, char*, __less<char>&);
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
extern template _LIBCPP_FUNC_VIS void __sort<__less<wchar_t>&, wchar_t*>(wchar_t*, wchar_t*, __less<wchar_t>&);
#endif
extern template _LIBCPP_FUNC_VIS void __sort<__less<signed char>&, signed char*>(signed char*, signed char*, __less<signed char>&);
extern template _LIBCPP_FUNC_VIS void __sort<__less<unsigned char>&, unsigned char*>(unsigned char*, unsigned char*, __less<unsigned char>&);
extern template _LIBCPP_FUNC_VIS void __sort<__less<short>&, short*>(short*, short*, __less<short>&);
extern template _LIBCPP_FUNC_VIS void __sort<__less<unsigned short>&, unsigned short*>(unsigned short*, unsigned short*, __less<unsigned short>&);
extern template _LIBCPP_FUNC_VIS void __sort<__less<int>&, int*>(int*, int*, __less<int>&);
extern template _LIBCPP_FUNC_VIS void __sort<__less<unsigned>&, unsigned*>(unsigned*, unsigned*, __less<unsigned>&);
extern template _LIBCPP_FUNC_VIS void __sort<__less<long>&, long*>(long*, long*, __less<long>&);
extern template _LIBCPP_FUNC_VIS void __sort<__less<unsigned long>&, unsigned long*>(unsigned long*, unsigned long*, __less<unsigned long>&);
extern template _LIBCPP_FUNC_VIS void __sort<__less<long long>&, long long*>(long long*, long long*, __less<long long>&);
extern template _LIBCPP_FUNC_VIS void __sort<__less<unsigned long long>&, unsigned long long*>(unsigned long long*, unsigned long long*, __less<unsigned long long>&);
extern template _LIBCPP_FUNC_VIS void __sort<__less<float>&, float*>(float*, float*, __less<float>&);
extern template _LIBCPP_FUNC_VIS void __sort<__less<double>&, double*>(double*, double*, __less<double>&);
extern template _LIBCPP_FUNC_VIS void __sort<__less<long double>&, long double*>(long double*, long double*, __less<long double>&);
template <class _AlgPolicy, class _RandomAccessIterator, class _Comp>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void
__sort_dispatch(_RandomAccessIterator __first, _RandomAccessIterator __last, _Comp& __comp) {
typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
difference_type __depth_limit = 2 * std::__log2i(__last - __first);
// Only use bitset partitioning for arithmetic types. We should also check
// that the default comparator is in use so that we are sure that there are no
// branches in the comparator.
std::__introsort<_AlgPolicy,
_Comp&,
_RandomAccessIterator,
__use_branchless_sort<_Comp, _RandomAccessIterator>::value>(
__first, __last, __comp, __depth_limit);
}
template <class _Type, class... _Options>
using __is_any_of = _Or<is_same<_Type, _Options>...>;
template <class _Type>
using __sort_is_specialized_in_library = __is_any_of<
_Type,
char,
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
wchar_t,
#endif
signed char,
unsigned char,
short,
unsigned short,
int,
unsigned int,
long,
unsigned long,
long long,
unsigned long long,
float,
double,
long double>;
template <class _AlgPolicy, class _Type, __enable_if_t<__sort_is_specialized_in_library<_Type>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI void __sort_dispatch(_Type* __first, _Type* __last, __less<_Type>& __comp) {
std::__sort<__less<_Type>&, _Type*>(__first, __last, __comp);
}
template <class _AlgPolicy, class _Type, __enable_if_t<__sort_is_specialized_in_library<_Type>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI void __sort_dispatch(_Type* __first, _Type* __last, less<_Type>&) {
__less<_Type> __comp;
std::__sort<__less<_Type>&, _Type*>(__first, __last, __comp);
}
#if _LIBCPP_STD_VER >= 14
template <class _AlgPolicy, class _Type, __enable_if_t<__sort_is_specialized_in_library<_Type>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI void __sort_dispatch(_Type* __first, _Type* __last, less<>&) {
__less<_Type> __comp;
std::__sort<__less<_Type>&, _Type*>(__first, __last, __comp);
}
#endif
#if _LIBCPP_STD_VER >= 20
template <class _AlgPolicy, class _Type, __enable_if_t<__sort_is_specialized_in_library<_Type>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI void __sort_dispatch(_Type* __first, _Type* __last, ranges::less&) {
__less<_Type> __comp;
std::__sort<__less<_Type>&, _Type*>(__first, __last, __comp);
}
#endif
template <class _AlgPolicy, class _RandomAccessIterator, class _Comp>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
void __sort_impl(_RandomAccessIterator __first, _RandomAccessIterator __last, _Comp& __comp) {
std::__debug_randomize_range<_AlgPolicy>(__first, __last);
if (__libcpp_is_constant_evaluated()) {
std::__partial_sort<_AlgPolicy>(
std::__unwrap_iter(__first), std::__unwrap_iter(__last), std::__unwrap_iter(__last), __comp);
} else {
std::__sort_dispatch<_AlgPolicy>(std::__unwrap_iter(__first), std::__unwrap_iter(__last), __comp);
}
}
template <class _RandomAccessIterator, class _Comp>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
void sort(_RandomAccessIterator __first, _RandomAccessIterator __last, _Comp __comp) {
std::__sort_impl<_ClassicAlgPolicy>(std::move(__first), std::move(__last), __comp);
}
template <class _RandomAccessIterator>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
void sort(_RandomAccessIterator __first, _RandomAccessIterator __last) {
std::sort(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
}
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___ALGORITHM_SORT_H
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