Counters

Detailed Description

Atomic counters types.

For an introduction with examples see Counters.

Three template specializations are provided. All satisfy the basic concept AtomicCounter :

T constraints	Clock constraints	Counter::ValueType	Notes	Link
Integral	-	T	Specialization is lock-free if std::atomic<T> is lock-free. Specialization can be fully lock-free on most architectures. Provides additional member functions like pre/post increment, FetchAdd/FetchSub. No internal timestamp.	Counter<T>
Non-Integral	-	T	Specialization is lock-free if std::atomic<T> is lock-free. No internal timestamp.	Counter<T>
None	Clock satisfy TrivialClock	Timestamped<T, TimePoint>	Default Clock is std::chrono::steady_clock. Keeps internal timestamp. Automatically updates timestamp on writes, if time is not provided by caller.	Counter<T, Clock>

Commonly used types have pre-defined aliases for double, signed and unsigned 64bit integer, with and without timestamp, see list below.

Note

As counters are potential synchronization objects they provide no copy or move constructor.

Files
file	counter.hpp
	Performance counter implementation.

Classes
struct	perfc::Timestamped< T, TimePoint >
	Trivial type describing a counter value and associated timestamp. More...
class	perfc::Counter< T, void, typename std::enable_if< std::is_integral< T >::value >::type >
	Integrals w/o timestamp Partial specialization for integral types T and without clock. More...
class	perfc::Counter< T, void, typename std::enable_if<!std::is_integral< T >::value >::type >
	Non-integrals w/o timestamp Partial specialization matching void clocks and non-integral T's. More...
class	perfc::Counter< T, Clock, typename std::enable_if<!std::is_void< Clock >::value >::type >
	With timestamp Partial specialization for non-void Clock type. More...

Enumerations
enum class	perfc::MemoryOrder : std::underlying_type_t< std::memory_order >
	Memory ordering constraints. More...

Aliases of timestamped counters
These aliases are using the clock std::steady_clock as a timestamp source.
using	perfc::CounterDoubleTs = Counter<double, std::chrono::steady_clock>
using	perfc::CounterU64Ts = Counter<std::uint64_t, std::chrono::steady_clock>
using	perfc::CounterI64Ts = Counter<std::int64_t, std::chrono::steady_clock>

Aliases of non-timestamped counters
These counters aliases have no internal timestamp and are very light weight and on most 64bit architectures they are fully lock-free.
using	perfc::CounterDouble = Counter<double, void>
using	perfc::CounterU64 = Counter<std::uint64_t, void>
using	perfc::CounterI64 = Counter<std::int64_t, void>

Synchronization functions
Provides capability to synchronize relaxed atomic counter reads and writes.
void	perfc::CounterAcquire () noexcept
	Synchronizes-with CounterRelease() or Counter store operations using MemoryOrder::Release.
void	perfc::CounterRelease () noexcept
	Synchronizes-with CounterAcquire() or counter load operations using MemoryOrder::Acquire.

Typedef Documentation

CounterDouble

using perfc::CounterDouble = Counter<double, void>

Definition at line 498 of file counter.hpp.

CounterDoubleTs

using perfc::CounterDoubleTs = Counter<double, std::chrono::steady_clock>

Definition at line 484 of file counter.hpp.

CounterI64

using perfc::CounterI64 = Counter<std::int64_t, void>

Definition at line 500 of file counter.hpp.

CounterI64Ts

using perfc::CounterI64Ts = Counter<std::int64_t, std::chrono::steady_clock>

Definition at line 486 of file counter.hpp.

CounterU64

using perfc::CounterU64 = Counter<std::uint64_t, void>

Definition at line 499 of file counter.hpp.

CounterU64Ts

using perfc::CounterU64Ts = Counter<std::uint64_t, std::chrono::steady_clock>

Definition at line 485 of file counter.hpp.

Enumeration Type Documentation

MemoryOrder

template<class T, class Clock = std::chrono::steady_clock, class = void>

enum class MemoryOrder : std::underlying_type_t< std::memory_order >

related

Memory ordering constraints.

Definition at line 81 of file counter.hpp.

Function Documentation

CounterAcquire()

void perfc::CounterAcquire ( )

inlinenoexcept

Synchronizes-with CounterRelease() or Counter store operations using MemoryOrder::Release.

CounterRelease() is only necessary ensure that preceding relaxed operations to Counter are synchronized with reads.

Definition at line 458 of file counter.hpp.

CounterRelease()

void perfc::CounterRelease ( )

inlinenoexcept

Synchronizes-with CounterAcquire() or counter load operations using MemoryOrder::Acquire.

CounterRelease() is only necessary ensure that preceding relaxed operations to Counter are synchronized with reads.

Definition at line 471 of file counter.hpp.