38#ifndef _GLIBCXX_BARRIER
39#define _GLIBCXX_BARRIER 1
41#pragma GCC system_header
43#if __cplusplus > 201703L
45#if __cpp_lib_atomic_wait && __cpp_aligned_new
51#define __cpp_lib_barrier 201907L
53namespace std _GLIBCXX_VISIBILITY(default)
55_GLIBCXX_BEGIN_NAMESPACE_VERSION
57 struct __empty_completion
59 _GLIBCXX_ALWAYS_INLINE
void
78 enum class __barrier_phase_t :
unsigned char { };
80 template<
typename _CompletionF>
83 using __atomic_phase_ref_t = std::__atomic_ref<__barrier_phase_t>;
84 using __atomic_phase_const_ref_t = std::__atomic_ref<const __barrier_phase_t>;
85 static constexpr auto __phase_alignment =
86 __atomic_phase_ref_t::required_alignment;
89 struct alignas(64) __state_t
91 alignas(__phase_alignment) __tickets_t __tickets;
94 ptrdiff_t _M_expected;
95 unique_ptr<__state_t[]> _M_state;
96 __atomic_base<ptrdiff_t> _M_expected_adjustment;
97 _CompletionF _M_completion;
99 alignas(__phase_alignment) __barrier_phase_t _M_phase;
102 _M_arrive(__barrier_phase_t __old_phase,
size_t __current)
104 const auto __old_phase_val =
static_cast<unsigned char>(__old_phase);
105 const auto __half_step =
106 static_cast<__barrier_phase_t
>(__old_phase_val + 1);
107 const auto __full_step =
108 static_cast<__barrier_phase_t
>(__old_phase_val + 2);
110 size_t __current_expected = _M_expected;
111 __current %= ((_M_expected + 1) >> 1);
113 for (
int __round = 0; ; ++__round)
115 if (__current_expected <= 1)
117 size_t const __end_node = ((__current_expected + 1) >> 1),
118 __last_node = __end_node - 1;
119 for ( ; ; ++__current)
121 if (__current == __end_node)
123 auto __expect = __old_phase;
124 __atomic_phase_ref_t __phase(_M_state[__current]
125 .__tickets[__round]);
126 if (__current == __last_node && (__current_expected & 1))
128 if (__phase.compare_exchange_strong(__expect, __full_step,
129 memory_order_acq_rel))
132 else if (__phase.compare_exchange_strong(__expect, __half_step,
133 memory_order_acq_rel))
137 else if (__expect == __half_step)
139 if (__phase.compare_exchange_strong(__expect, __full_step,
140 memory_order_acq_rel))
144 __current_expected = __last_node + 1;
150 using arrival_token = __barrier_phase_t;
152 static constexpr ptrdiff_t
154 {
return __PTRDIFF_MAX__; }
156 __tree_barrier(ptrdiff_t __expected, _CompletionF __completion)
157 : _M_expected(__expected), _M_expected_adjustment(0),
158 _M_completion(
move(__completion)),
159 _M_phase(static_cast<__barrier_phase_t>(0))
161 size_t const __count = (_M_expected + 1) >> 1;
163 _M_state = std::make_unique<__state_t[]>(__count);
166 [[nodiscard]] arrival_token
167 arrive(ptrdiff_t __update)
171 __atomic_phase_ref_t __phase(_M_phase);
172 const auto __old_phase = __phase.load(memory_order_relaxed);
173 const auto __cur =
static_cast<unsigned char>(__old_phase);
174 for(; __update; --__update)
176 if(_M_arrive(__old_phase, __current))
179 _M_expected += _M_expected_adjustment.load(memory_order_relaxed);
180 _M_expected_adjustment.store(0, memory_order_relaxed);
181 auto __new_phase =
static_cast<__barrier_phase_t
>(__cur + 2);
182 __phase.store(__new_phase, memory_order_release);
183 __phase.notify_all();
190 wait(arrival_token&& __old_phase)
const
192 __atomic_phase_const_ref_t __phase(_M_phase);
193 auto const __test_fn = [=]
195 return __phase.load(memory_order_acquire) != __old_phase;
197 std::__atomic_wait_address(&_M_phase, __test_fn);
203 _M_expected_adjustment.fetch_sub(1, memory_order_relaxed);
208 template<
typename _CompletionF = __empty_completion>
213 using __algorithm_t = __tree_barrier<_CompletionF>;
217 class arrival_token final
220 arrival_token(arrival_token&&) =
default;
221 arrival_token& operator=(arrival_token&&) =
default;
222 ~arrival_token() =
default;
225 friend class barrier;
226 using __token =
typename __algorithm_t::arrival_token;
227 explicit arrival_token(__token __tok) noexcept : _M_tok(__tok) { }
231 static constexpr ptrdiff_t
233 {
return __algorithm_t::max(); }
236 barrier(ptrdiff_t __count, _CompletionF __completion = _CompletionF())
237 : _M_b(__count,
std::
move(__completion))
240 barrier(barrier
const&) =
delete;
241 barrier& operator=(barrier
const&) =
delete;
243 [[nodiscard]] arrival_token
244 arrive(ptrdiff_t __update = 1)
245 {
return arrival_token{_M_b.arrive(__update)}; }
248 wait(arrival_token&& __phase)
const
249 { _M_b.wait(
std::move(__phase._M_tok)); }
257 { _M_b.arrive_and_drop(); }
260_GLIBCXX_END_NAMESPACE_VERSION
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
ISO C++ entities toplevel namespace is std.
thread::id get_id() noexcept
The unique identifier of the current thread.
A standard container for storing a fixed size sequence of elements.
Primary class template hash.