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std::atomic_compare_exchange_weak, std::atomic_compare_exchange_strong, std::atomic_compare_exchange_weak_explicit, std::atomic_compare_exchange_strong_explicit

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< cpp‎ | atomic

 
 
Atomique opérations de la bibliothèque
Types
Original:
Types
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atomic (C++11)
atomic_is_lock_free (C++11)
Fonctions
Original:
Functions
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atomic_store
atomic_store_explicit
(C++11)
(C++11)
atomic_load
atomic_load_explicit
(C++11)
(C++11)
atomic_exchange
atomic_exchange_explicit
(C++11)
(C++11)
atomic_compare_exchange_weak
atomic_compare_exchange_weak_explicit
atomic_compare_exchange_strong
atomic_compare_exchange_strong_explicit
(C++11)
(C++11)
(C++11)
(C++11)
atomic_fetch_add
atomic_fetch_add_explicit
(C++11)
(C++11)
atomic_fetch_sub
atomic_fetch_sub_explicit
(C++11)
(C++11)
atomic_fetch_and
atomic_fetch_and_explicit
(C++11)
(C++11)
atomic_fetch_or
atomic_fetch_or_explicit
(C++11)
(C++11)
atomic_fetch_xor
atomic_fetch_xor_explicit
(C++11)
(C++11)
Drapeaux atomiques
Original:
Atomic flags
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atomic_flag (C++11)
atomic_flag_test_and_set
atomic_flag_test_and_set_explicit
(C++11)
(C++11)
atomic_flag_clear
atomic_flag_clear_explicit
(C++11)
(C++11)
Initialisation
Original:
Initialization
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atomic_init (C++11)
ATOMIC_VAR_INIT (C++11)
ATOMIC_FLAG_INIT (C++11)
Mémoire de la commande
Original:
Memory ordering
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memory_order (C++11)
kill_dependency (C++11)
atomic_thread_fence (C++11)
atomic_signal_fence (C++11)
 
Defined in header <atomic>
template< class T >

bool atomic_compare_exchange_weak( std::atomic<T>* obj,
                                   T* expected, T desired );
template< class T >
bool atomic_compare_exchange_weak( volatile std::atomic<T>* obj,

                                   T* expected, T desired );
(1) (depuis C++11)
template< class T >

bool atomic_compare_exchange_strong( std::atomic<T>* obj,
                                     T* expected, T desired );
template< class T >
bool atomic_compare_exchange_strong( volatile std::atomic<T>* obj,

                                     T* expected, T desired );
(2) (depuis C++11)
template< class T >

bool atomic_compare_exchange_weak_explicit( std::atomic<T>* obj,
                                            T* expected, T desired,
                                            std::memory_order succ,
                                            std::memory_order fail );
template< class T >
bool atomic_compare_exchange_weak_explicit( volatile std::atomic<T>* obj,
                                            T* expected, T desired,
                                            std::memory_order succ,

                                            std::memory_order fail );
(3) (depuis C++11)
template< class T >

bool atomic_compare_exchange_strong_explicit( std::atomic<T>* obj,
                                              T* expected, T desired,
                                              std::memory_order succ,
                                              std::memory_order fail );
template< class T >
bool atomic_compare_exchange_strong_explicit( volatile std::atomic<T>* obj,
                                              T* expected, T desired,
                                              std::memory_order succ,

                                              std::memory_order fail );
(4) (depuis C++11)
Compare atomiquement la valeur pointée par obj avec la valeur pointée par expected, et si ceux-ci sont égaux, remplace l'ancien desired (effectue lecture-modification-écriture). Dans le cas contraire, la valeur réelle charge pointée par obj en *expected (effectue une opération de charge) .
Original:
Atomically compares the value pointed to by obj with the value pointed to by expected, and if those are equal, replaces the former with desired (performs read-modify-write operation). Otherwise, loads the actual value pointed to by obj into *expected (performs load operation).
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Les modèles de la mémoire pour la lecture-modification-écriture et les opérations de chargement et sont succ fail respectivement. Les versions (1-2) std::memory_order_seq_cst utiliser par défaut .
Original:
The memory models for the read-modify-write and load operations are succ and fail respectively. The (1-2) versions use std::memory_order_seq_cst by default.
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Les formes faibles ((1) et (3)) des fonctions sont autorisés à ne pas faussement, qui est, comme si *obj != *expected même si elles sont égales. Quand une comparaison et d'échange est dans une boucle, la version faible donnera de meilleures performances sur certaines plates-formes. Quand un faible compare-and-échange, il faudrait une boucle et une forte ne serait pas, le fort est préférable .
Original:
The weak forms ((1) and (3)) of the functions are allowed to fail spuriously, that is, act as if *obj != *expected even if they are equal. When a compare-and-exchange is in a loop, the weak version will yield better performance on some platforms. When a weak compare-and-exchange would require a loop and a strong one would not, the strong one is preferable.
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Ces fonctions sont définies en termes de fonctions membres de std::atomic:
Original:
These functions are defined in terms of member functions of std::atomic:
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1) obj->compare_exchange_weak(exp, desr)
2) obj->compare_exchange_strong(exp, desr)
3) obj->compare_exchange_weak(exp, desr, succ, fail)
4) obj->compare_exchange_strong(exp, desr, succ, fail)

Sommaire

[modifier] Paramètres

obj -
pointeur vers l'objet atomique pour tester et modifier
Original:
pointer to the atomic object to test and modify
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expected -
pointeur à la valeur prévue pour être trouvé dans l'objet atomique
Original:
pointer to the value expected to be found in the atomic object
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desired -
la valeur à stocker dans l'objet atomique si elle est conforme aux attentes
Original:
the value to store in the atomic object if it is as expected
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succ -
la sycnhronization mémoire de commande pour la lecture-modification-écriture, si la comparaison aboutit. Toutes les valeurs sont permises .
Original:
the memory sycnhronization ordering for the read-modify-write operation if the comparison succeeds. All values are permitted.
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fail -
sycnhronization la mémoire de commande pour l'opération de chargement si la comparaison échoue. Ne peut pas être std::memory_order_release ou std::memory_order_ack_rel et ne pouvez pas spécifier plus forte que succ ordre
Original:
the memory sycnhronization ordering for the load operation if the comparison fails. Cannot be std::memory_order_release or std::memory_order_ack_rel and cannot specify stronger ordering than succ
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[modifier] Retourne la valeur

Le résultat de la comparaison: si true *obj était égal à *exp, false autrement .
Original:
The result of the comparison: true if *obj was equal to *exp, false otherwise.
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[modifier] Exceptions

noexcept specification:  
noexcept
   (depuis C++11)

[modifier] Exemple

Cet exemple montre comment compare-and-échange peuvent être utilisés pour mettre en œuvre sans verrou ajout à une liste simplement chaînée
Original:
This example shows how compare-and-exchange may be used to implement lock-free append to a singly linked list
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void append(list* s, node* n)
{
    node* head;
    do {
        head = s->head;
        n->next = head;
    } while(! std::atomic_compare_exchange_weak(s->head, head, n));
}


[modifier] Voir aussi

compare atomiquement la valeur de l'objet atomique non atomique avec l'argument, et réalise un échange atomique égal ou si la charge atomique sinon
Original:
atomically compares the value of the atomic object with non-atomic argument and performs atomic exchange if equal or atomic load if not
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(fonction membre publique de std::atomic) [edit]
remplace atomiquement la valeur de l'objet atomique avec des non-atomique argument et retourne l'ancienne valeur de la bombe atomique
Original:
atomically replaces the value of the atomic object with non-atomic argument and returns the old value of the atomic
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(fonction générique) [edit]
se spécialise opérations atomiques pour std :: shared_ptr
Original:
specializes atomic operations for std::shared_ptr
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(fonction générique)
C documentation for atomic_compare_exchange, atomic_compare_exchange_explicit