+ /// Atomic cache-friendly item counter
+ /**
+ Atomic item counter with cache-line padding to avoid false sharing.
+ Adding cache-line padding before and after atomic counter eliminates the contention
+ in read path of many containers and can notably improve search operations in sets/maps.
+ */
+ class cache_friendly_item_counter
+ {
+ public:
+ typedef atomics::atomic_size_t atomic_type; ///< atomic type used
+ typedef size_t counter_type; ///< Integral item counter type (size_t)
+
+ private:
+ //@cond
+ char pad1_[cds::c_nCacheLineSize];
+ atomic_type m_Counter; ///< Atomic item counter
+ char pad2_[cds::c_nCacheLineSize - sizeof( atomic_type )];
+ //@endcond
+
+ public:
+ /// Default ctor initializes the counter to zero.
+ cache_friendly_item_counter()
+ : m_Counter(counter_type(0))
+ {}
+
+ /// Returns current value of the counter
+ counter_type value(atomics::memory_order order = atomics::memory_order_relaxed) const
+ {
+ return m_Counter.load( order );
+ }
+
+ /// Same as \ref value() with relaxed memory ordering
+ operator counter_type() const
+ {
+ return value();
+ }
+
+ /// Returns underlying atomic interface
+ atomic_type& getAtomic()
+ {
+ return m_Counter;
+ }
+
+ /// Returns underlying atomic interface (const)
+ const atomic_type& getAtomic() const
+ {
+ return m_Counter;
+ }
+
+ /// Increments the counter. Semantics: postincrement
+ counter_type inc(atomics::memory_order order = atomics::memory_order_relaxed )
+ {
+ return m_Counter.fetch_add( 1, order );
+ }
+
+ /// Increments the counter. Semantics: postincrement
+ counter_type inc( counter_type count, atomics::memory_order order = atomics::memory_order_relaxed )
+ {
+ return m_Counter.fetch_add( count, order );
+ }
+
+ /// Decrements the counter. Semantics: postdecrement
+ counter_type dec(atomics::memory_order order = atomics::memory_order_relaxed)
+ {
+ return m_Counter.fetch_sub( 1, order );
+ }
+
+ /// Decrements the counter. Semantics: postdecrement
+ counter_type dec( counter_type count, atomics::memory_order order = atomics::memory_order_relaxed )
+ {
+ return m_Counter.fetch_sub( count, order );
+ }
+
+ /// Preincrement
+ counter_type operator ++()
+ {
+ return inc() + 1;
+ }
+ /// Postincrement
+ counter_type operator ++(int)
+ {
+ return inc();
+ }
+
+ /// Predecrement
+ counter_type operator --()
+ {
+ return dec() - 1;
+ }
+ /// Postdecrement
+ counter_type operator --(int)
+ {
+ return dec();
+ }
+
+ /// Increment by \p count
+ counter_type operator +=( counter_type count )
+ {
+ return inc( count ) + count;
+ }
+
+ /// Decrement by \p count
+ counter_type operator -=( counter_type count )
+ {
+ return dec( count ) - count;
+ }
+
+ /// Resets count to 0
+ void reset(atomics::memory_order order = atomics::memory_order_relaxed)
+ {
+ m_Counter.store( 0, order );
+ }
+ };
+
+
projects / libcds.git / commitdiff