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std::hardware_destructive_interference_size, std::hardware_constructive_interference_size

Defined in header <new> 
static constexpr std::size_t
    hardware_destructive_interference_size = /*implementation-defined*/;
 (1) (since C++17) 
static constexpr std::size_t
    hardware_constructive_interference_size = /*implementation-defined*/;
 (2) (since C++17)
1) Minimum offset between two objects to avoid false sharing. Guaranteed to be at least alignof(std::max_align_t) 
struct keep_apart {
  alignas(std::hardware_destructive_interference_size) std::atomic<int> cat;
  alignas(std::hardware_destructive_interference_size) std::atomic<int> dog;
};
2) Maximum size of contiguous memory to promote true sharing. Guaranteed to be at least alignof(max_align_t) 
struct together {
  atomic<int> dog;
  int puppy;
};
struct kennel {
  // Other data members...
  alignas(sizeof(together)) together pack;
  // Other data members...
};
static_assert(sizeof(together) <= std::hardware_constructive_interference_size);

Notes

These constants provide a portable way to access the L1 data cache line size.

Example

See also

[static]
 returns the number of concurrent threads supported by the implementation
(public static member function of std::thread)

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