33 #ifndef _GLIBCXX_BARRIER 34 #define _GLIBCXX_BARRIER 1 36 #pragma GCC system_header 38 #if __cplusplus > 201703L 40 #if __cpp_lib_atomic_wait && __cpp_aligned_new 46 #define __cpp_lib_barrier 201907L 48 namespace std _GLIBCXX_VISIBILITY(default)
50 _GLIBCXX_BEGIN_NAMESPACE_VERSION
52 struct __empty_completion
54 _GLIBCXX_ALWAYS_INLINE
void 73 enum class __barrier_phase_t : unsigned char { };
75 template<
typename _CompletionF>
78 using __atomic_phase_ref_t = std::__atomic_ref<__barrier_phase_t>;
79 using __atomic_phase_const_ref_t = std::__atomic_ref<const __barrier_phase_t>;
80 static constexpr
auto __phase_alignment =
81 __atomic_phase_ref_t::required_alignment;
84 struct alignas(64) __state_t
86 alignas(__phase_alignment) __tickets_t __tickets;
89 ptrdiff_t _M_expected;
90 unique_ptr<__state_t[]> _M_state;
91 __atomic_base<ptrdiff_t> _M_expected_adjustment;
92 _CompletionF _M_completion;
94 alignas(__phase_alignment) __barrier_phase_t _M_phase;
97 _M_arrive(__barrier_phase_t __old_phase,
size_t __current)
99 const auto __old_phase_val =
static_cast<unsigned char>(__old_phase);
100 const auto __half_step =
101 static_cast<__barrier_phase_t
>(__old_phase_val + 1);
102 const auto __full_step =
103 static_cast<__barrier_phase_t
>(__old_phase_val + 2);
105 size_t __current_expected = _M_expected;
107 __current %= ((_M_expected + 1) >> 1);
109 for (
int __round = 0; ; ++__round)
111 if (__current_expected <= 1)
113 size_t const __end_node = ((__current_expected + 1) >> 1),
114 __last_node = __end_node - 1;
115 for ( ; ; ++__current)
117 if (__current == __end_node)
119 auto __expect = __old_phase;
120 __atomic_phase_ref_t __phase(_M_state[__current]
121 .__tickets[__round]);
122 if (__current == __last_node && (__current_expected & 1))
124 if (__phase.compare_exchange_strong(__expect, __full_step,
125 memory_order_acq_rel))
128 else if (__phase.compare_exchange_strong(__expect, __half_step,
129 memory_order_acq_rel))
133 else if (__expect == __half_step)
135 if (__phase.compare_exchange_strong(__expect, __full_step,
136 memory_order_acq_rel))
140 __current_expected = __last_node + 1;
146 using arrival_token = __barrier_phase_t;
148 static constexpr ptrdiff_t
150 {
return __PTRDIFF_MAX__; }
152 __tree_barrier(ptrdiff_t __expected, _CompletionF __completion)
153 : _M_expected(__expected), _M_expected_adjustment(0),
154 _M_completion(
move(__completion)),
155 _M_phase(static_cast<__barrier_phase_t>(0))
157 size_t const __count = (_M_expected + 1) >> 1;
159 _M_state = std::make_unique<__state_t[]>(__count);
162 [[nodiscard]] arrival_token
163 arrive(ptrdiff_t __update)
167 __atomic_phase_ref_t __phase(_M_phase);
168 const auto __old_phase = __phase.load(memory_order_relaxed);
169 const auto __cur =
static_cast<unsigned char>(__old_phase);
170 for(; __update; --__update)
172 if(_M_arrive(__old_phase, __current))
175 _M_expected += _M_expected_adjustment.load(memory_order_relaxed);
176 _M_expected_adjustment.store(0, memory_order_relaxed);
177 auto __new_phase =
static_cast<__barrier_phase_t
>(__cur + 2);
178 __phase.store(__new_phase, memory_order_release);
179 __phase.notify_all();
186 wait(arrival_token&& __old_phase)
const 188 __atomic_phase_const_ref_t __phase(_M_phase);
189 auto const __test_fn = [=]
191 return __phase.load(memory_order_acquire) != __old_phase;
193 std::__atomic_wait_address(&_M_phase, __test_fn);
199 _M_expected_adjustment.fetch_sub(1, memory_order_relaxed);
204 template<
typename _CompletionF = __empty_completion>
209 using __algorithm_t = __tree_barrier<_CompletionF>;
213 class arrival_token final
216 arrival_token(arrival_token&&) =
default;
217 arrival_token&
operator=(arrival_token&&) =
default;
218 ~arrival_token() =
default;
221 friend class barrier;
222 using __token =
typename __algorithm_t::arrival_token;
223 explicit arrival_token(__token __tok) noexcept : _M_tok(__tok) { }
227 static constexpr ptrdiff_t
232 barrier(ptrdiff_t __count, _CompletionF __completion = _CompletionF())
233 : _M_b(__count,
std::
move(__completion))
236 barrier(barrier
const&) =
delete;
237 barrier&
operator=(barrier
const&) =
delete;
239 [[nodiscard]] arrival_token
240 arrive(ptrdiff_t __update = 1)
241 {
return arrival_token{_M_b.arrive(__update)}; }
244 wait(arrival_token&& __phase)
const 245 { _M_b.wait(
std::move(__phase._M_tok)); }
253 { _M_b.arrive_and_drop(); }
256 _GLIBCXX_END_NAMESPACE_VERSION
258 #endif // __cpp_lib_atomic_wait && __cpp_aligned_new 259 #endif // __cplusplus > 201703L 260 #endif // _GLIBCXX_BARRIER thread::id get_id() noexcept
this_thread::get_id
A standard container for storing a fixed size sequence of elements.
Primary class template hash.
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
constexpr const _Tp & max(const _Tp &, const _Tp &)
This does what you think it does.
ISO C++ entities toplevel namespace is std.
auto_ptr & operator=(auto_ptr &__a)
auto_ptr assignment operator.