38#ifndef _GLIBCXX_BARRIER
39#define _GLIBCXX_BARRIER 1
42#pragma GCC system_header
47#define __glibcxx_want_barrier
50#ifdef __cpp_lib_barrier
57namespace std _GLIBCXX_VISIBILITY(default)
59_GLIBCXX_BEGIN_NAMESPACE_VERSION
61 struct __empty_completion
63 _GLIBCXX_ALWAYS_INLINE
void
82 enum class __barrier_phase_t :
unsigned char { };
84 template<
typename _CompletionF>
87 using __atomic_phase_ref_t = std::__atomic_ref<__barrier_phase_t>;
88 using __atomic_phase_const_ref_t = std::__atomic_ref<const __barrier_phase_t>;
89 static constexpr auto __phase_alignment =
90 __atomic_phase_ref_t::required_alignment;
93 struct alignas(64) __state_t
95 alignas(__phase_alignment) __tickets_t __tickets;
98 ptrdiff_t _M_expected;
99 unique_ptr<__state_t[]> _M_state;
100 __atomic_base<ptrdiff_t> _M_expected_adjustment;
101 _CompletionF _M_completion;
103 alignas(__phase_alignment) __barrier_phase_t _M_phase;
106 _M_arrive(__barrier_phase_t __old_phase,
size_t __current)
108 const auto __old_phase_val =
static_cast<unsigned char>(__old_phase);
109 const auto __half_step =
110 static_cast<__barrier_phase_t
>(__old_phase_val + 1);
111 const auto __full_step =
112 static_cast<__barrier_phase_t
>(__old_phase_val + 2);
114 size_t __current_expected = _M_expected;
115 __current %= ((_M_expected + 1) >> 1);
117 for (
int __round = 0; ; ++__round)
119 if (__current_expected <= 1)
121 size_t const __end_node = ((__current_expected + 1) >> 1),
122 __last_node = __end_node - 1;
123 for ( ; ; ++__current)
125 if (__current == __end_node)
127 auto __expect = __old_phase;
128 __atomic_phase_ref_t __phase(_M_state[__current]
129 .__tickets[__round]);
130 if (__current == __last_node && (__current_expected & 1))
132 if (__phase.compare_exchange_strong(__expect, __full_step,
133 memory_order_acq_rel))
136 else if (__phase.compare_exchange_strong(__expect, __half_step,
137 memory_order_acq_rel))
141 else if (__expect == __half_step)
143 if (__phase.compare_exchange_strong(__expect, __full_step,
144 memory_order_acq_rel))
148 __current_expected = __last_node + 1;
154 using arrival_token = __barrier_phase_t;
156 static constexpr ptrdiff_t
158 {
return __PTRDIFF_MAX__; }
160 __tree_barrier(ptrdiff_t __expected, _CompletionF __completion)
161 : _M_expected(__expected), _M_expected_adjustment(0),
162 _M_completion(
move(__completion)),
163 _M_phase(static_cast<__barrier_phase_t>(0))
165 size_t const __count = (_M_expected + 1) >> 1;
167 _M_state = std::make_unique<__state_t[]>(__count);
170 [[nodiscard]] arrival_token
171 arrive(ptrdiff_t __update)
175 __atomic_phase_ref_t __phase(_M_phase);
176 const auto __old_phase = __phase.load(memory_order_relaxed);
177 const auto __cur =
static_cast<unsigned char>(__old_phase);
178 for(; __update; --__update)
180 if(_M_arrive(__old_phase, __current))
183 _M_expected += _M_expected_adjustment.load(memory_order_relaxed);
184 _M_expected_adjustment.store(0, memory_order_relaxed);
185 auto __new_phase =
static_cast<__barrier_phase_t
>(__cur + 2);
186 __phase.store(__new_phase, memory_order_release);
187 __phase.notify_all();
194 wait(arrival_token&& __old_phase)
const
196 __atomic_phase_const_ref_t __phase(_M_phase);
197 auto const __test_fn = [=]
199 return __phase.load(memory_order_acquire) != __old_phase;
201 std::__atomic_wait_address(&_M_phase, __test_fn);
207 _M_expected_adjustment.fetch_sub(1, memory_order_relaxed);
212 template<
typename _CompletionF = __empty_completion>
217 using __algorithm_t = __tree_barrier<_CompletionF>;
221 class arrival_token final
224 arrival_token(arrival_token&&) =
default;
225 arrival_token& operator=(arrival_token&&) =
default;
226 ~arrival_token() =
default;
229 friend class barrier;
230 using __token =
typename __algorithm_t::arrival_token;
231 explicit arrival_token(__token __tok) noexcept : _M_tok(__tok) { }
235 static constexpr ptrdiff_t
237 {
return __algorithm_t::max(); }
240 barrier(ptrdiff_t __count, _CompletionF __completion = _CompletionF())
241 : _M_b(__count,
std::
move(__completion))
244 barrier(barrier
const&) =
delete;
245 barrier& operator=(barrier
const&) =
delete;
247 [[nodiscard]] arrival_token
248 arrive(ptrdiff_t __update = 1)
249 {
return arrival_token{_M_b.arrive(__update)}; }
252 wait(arrival_token&& __phase)
const
253 { _M_b.wait(
std::move(__phase._M_tok)); }
261 { _M_b.arrive_and_drop(); }
264_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.