seqan3::detail::reader_writer_manager Class Reference

A single-use synchronisation point for closable concurrent data structures. More...

#include <seqan3/utility/parallel/detail/reader_writer_manager.hpp>

Classes
class	scoped_reader_type
	A strictly scope-based seqan3::detail::reader_writer_manager wrapper for consumer threads. More...
class	scoped_writer_type
	A strictly scope-based seqan3::detail::reader_writer_manager wrapper for producer threads. More...

Public Member Functions
void	reader_arrive () noexcept
	Atomically decrements reader counter by one.
void	reader_arrive_and_wait () noexcept
	Atomically decrements writer counter by one and blocks the calling thread.
scoped_reader_type	register_reader () noexcept
	Registers the current thread as a consumer thread for the monitored resource.
scoped_writer_type	register_writer () noexcept
	Registers the current thread as a producer thread for the monitored resource.
void	writer_arrive () noexcept
	Atomically decrements writer counter by one.
void	writer_arrive_and_wait () noexcept
	Atomically decrements writer counter by one and blocks the calling thread.
Constructors, destructor and assignment
	reader_writer_manager ()=delete
	Deleted.
	reader_writer_manager (reader_writer_manager const &)=delete
	Deleted.
	reader_writer_manager (reader_writer_manager &&)=delete
	Deleted.
reader_writer_manager &	operator= (reader_writer_manager const &)=delete
	Deleted.
reader_writer_manager &	operator= (reader_writer_manager &&)=delete
	Deleted.
	~reader_writer_manager ()=default
	Defaulted.
template<typename concurrent_t > requires requires { std::declval<concurrent_t>().close(); }
	reader_writer_manager (reader_count const rcount, writer_count const wcount, concurrent_t &ds)
	Constructs the reader_writer_manager with the reader count, writer count and the associated data structure.

Private Attributes
std::function< void()>	completion_fn
	The stored completion function.
std::once_flag	flag
	This flag ensures that the completion phase is invoked only once.
latch	reader_latch
	The internal latch for consumer threads.
latch	writer_latch
	The internal latch for producer threads.

Detailed Description

A single-use synchronisation point for closable concurrent data structures.

A reader writer manager is a thread coordination mechanism specifically designed to synchronise with a concurrent data structure such as the seqan3::detail::buffer_queue. In particular, the manager is constructed with a seqan3::detail::reader_count and a seqan3::detail::writer_count and offers special functions for readers and writers that arrive at the synchronisation point. If all writers arrived at the synchronisation point the associated concurrent data structure is closed by invoking the member method close(). This so called completion phase is triggered by only one of the participating producer threads. Accordingly, no more data can be added to the concurrent data structure and possibly waiting readers on an empty data structure can be released. The destructor of the reader_writer_manager will wait until all readers and writers arrived at the synchronisation point. Thus, a concurrent data structure can be safely destructed after the reader_writer_manager is destructed.

The class offers functions to register participating producer and consumer threads, which will signal if they are done when their destructor is called.

The reader_writer_manager class is neither copyable nor movable due to internal members used for inter thread synchronisation. Accordingly, the class is not default constructible.

Constructor & Destructor Documentation

reader_writer_manager()

template<typename concurrent_t >
requires requires { std::declval<concurrent_t>().close(); }

seqan3::detail::reader_writer_manager::reader_writer_manager ( reader_count const  rcount, writer_count const  wcount, concurrent_t &  ds  )

inline

Constructs the reader_writer_manager with the reader count, writer count and the associated data structure.

Template Parameters

concurrent_t

The type of the concurrent data structure. Must have a member function close.

Parameters

rcount	The expected number of consumer threads. Must be at least one.
wcount	The expected number of producer threads. Must be at least one.
ds	The concurrent data structure.

Initialises a std::contrib::latch for the consumer threads and a std::contrib::latch for the producer threads. Initialises the completion function which calls ds.close() on completion. Note, only a reference to the concurrent data structure is stored. The caller must ensure that ds is not destructed before this.

Exception

Throws std::invalid_argument if reader count or writer count is less than 1.

Member Function Documentation

reader_arrive()

void seqan3::detail::reader_writer_manager::reader_arrive ( )

inlinenoexcept

Atomically decrements reader counter by one.

Arrives at the synchronisation point for consumer threads without blocking the calling thread.

Exception

Guaranteed not to throw.

Thread safety

Thread-safe.

reader_arrive_and_wait()

void seqan3::detail::reader_writer_manager::reader_arrive_and_wait ( )

inlinenoexcept

Atomically decrements writer counter by one and blocks the calling thread.

Arrives at the synchronisation point for consumer threads and blocks the calling thread until all participating threads have arrived.

Exception

Guaranteed not to throw.

Thread safety

Thread-safe.

register_reader()

scoped_reader_type seqan3::detail::reader_writer_manager::register_reader ( )

inlinenoexcept

Registers the current thread as a consumer thread for the monitored resource.

Returns

A RAII wrapper class that automatically deregisters from the monitored resource when destructed.

If a thread calls this function it will become a participating consumer thread for the monitored concurrent data structure. On destruction of the returned RAII wrapper class seqan3::detail::reader_writer_manager::reader_arrive is called automatically.

Exception

Guaranteed not to throw.

Thread safety

Thread-safe.

register_writer()

scoped_writer_type seqan3::detail::reader_writer_manager::register_writer ( )

inlinenoexcept

Registers the current thread as a producer thread for the monitored resource.

Returns

A RAII wrapper class that automatically deregisters from the monitored resource when destructed.

If a thread calls this function it will become a participating producer thread for the monitored concurrent data structure. On destruction of the returned RAII wrapper class seqan3::detail::reader_writer_manager::writer_arrive is called automatically.

Exception

Guaranteed not to throw.

Thread safety

Thread-safe.

writer_arrive()

void seqan3::detail::reader_writer_manager::writer_arrive ( )

inlinenoexcept

Atomically decrements writer counter by one.

Arrives at the synchronisation point for producer threads without blocking the calling thread. If all participating producer threads arrived at the synchronisation point, one of the threads will invoke the completion function.

Exception

Guaranteed not to throw.

Thread safety

Thread-safe.

writer_arrive_and_wait()

void seqan3::detail::reader_writer_manager::writer_arrive_and_wait ( )

inlinenoexcept

Atomically decrements writer counter by one and blocks the calling thread.

Arrives at the synchronisation point for producer threads and blocks the calling thread until all participating threads have arrived. If all participating producer threads arrived at the synchronisation point, one of the threads will invoke the completion function.

Exception

Guaranteed not to throw.

Thread safety

Thread-safe.

---

The documentation for this class was generated from the following file:

• reader_writer_manager.hpp