EnableObserverPointer Class Reference

#include <deal.II/base/enable_observer_pointer.h>

Inherited by AffineConstraints< Number >, AffineConstraints< double >, AffineConstraints< value_type >, AffineConstraints< typename MatrixType::value_type >, AffineConstraints< typename VectorType::value_type >, BlockMatrixBase< SparseMatrix< number > >, BlockMatrixBase< SparseMatrix< Number, ::MemorySpace::Host > >, BlockMatrixBase< SparseMatrix >, BlockMatrixBase< SparseMatrix< double > >, DataPostprocessor< spacedim >, DiagonalMatrix< LinearAlgebra::distributed::Vector< double > >, DoFHandler< dim, spacedim >, DoFHandler< dim, dim >, DoFHandler< patch_dim, spacedim >, DoFHandler< 1, spacedim >, FETools::FEFactoryBase< FE::dimension, FE::space_dimension >, FEValuesBase< dim, dim >, FEValuesBase< dim1, dim1 >, FiniteElement< dim, spacedim >, FiniteElement< dim, dim >, FiniteElement< 1, spacedim >, FiniteElement< 2, 2 >, FiniteElement< PolynomialType::dimension+1, PolynomialType::dimension+1 >, Function< dim, double >, Function< dim, VectorType::value_type >, Function< 2 >, Function< 1 >, Function< dim+1 >, GridTools::Cache< dim, dim >, LinearAlgebra::TpetraWrappers::SparseMatrix< Number, MemorySpace >, MGCoarseGridBase< Vector< double > >, MGLevelObject< RelaxationType >, MGLevelObject< LinearAlgebra::distributed::Vector< Number > >, MGLevelObject< MatrixType >, MGLevelObject< LinearOperator< BlockVector< number > > >, MGLevelObject< PreconditionerType >, MGLevelObject< LinearOperator< VectorType > >, MGLevelObject< MGTwoLevelTransfer< dim, LinearAlgebra::distributed::Vector > >, MGLevelObject< ObserverPointer< MGTwoLevelTransferBase< LinearAlgebra::distributed::Vector > > >, MGLevelObject< std::shared_ptr< const Utilities::MPI::Partitioner > >, MGLevelObject< VectorType >, MGLevelObject< LinearOperator< Vector< double > > >, MGLevelObject< SparsityPattern >, MGLevelObject< SparseMatrix< number > >, MGMatrixBase< Vector< number > >, MGMatrixBase< Vector< double > >, MGSmootherBase< BlockVector< number > >, MGSmootherBase< Vector< double > >, MGTransferBase< LinearAlgebra::distributed::Vector< Number > >, MGTransferBase< BlockVector< number > >, MGTransferBase< LinearAlgebra::distributed::BlockVector< Number > >, MGTransferBase< Vector< number > >, MGTwoLevelTransferBase< LinearAlgebra::distributed::Vector >, Manifold< dim, spacedim >, Manifold< dim, dim >, Mapping< dim, spacedim >, Mapping< dim, dim >, Mapping< patch_dim, spacedim >, MatrixBlock< FullMatrix< double > >, MatrixBlock< FullMatrix< number > >, MatrixFree< dim, Number, VectorizedArrayType >, MatrixFree< dim, double, VectorizedArray< double > >, MatrixFree< dim, value_type, VectorizedArray< typename VectorType::value_type > >, MatrixFree< dim, Number >, MatrixFree< dim, Number, VectorizedArray< Number > >, MatrixFreeOperators::Base< dim, LinearAlgebra::distributed::Vector< double >, VectorizedArray< typename VectorType::value_type > >, NonMatching::MappingInfo< dim, spacedim, double >, NonMatching::MappingInfo< dim, dim, double >, NonMatching::MappingInfo< dim, dim, Number >, Polynomials::Polynomial< double >, PreconditionBlock< MatrixType, typename MatrixType::value_type > [virtual], PreconditionBlock< MatrixType, inverse_type > [virtual], PreconditionBlockJacobi< MatrixType, inverse_type > [virtual], PreconditionBlockSOR< MatrixType, typename MatrixType::value_type > [virtual], PreconditionRelaxation< SparseMatrix< double >, internal::PreconditionRelaxation::PreconditionJacobiImpl< SparseMatrix< double > > >, PreconditionRelaxation< SparseMatrix< double >, internal::PreconditionRelaxation::PreconditionPSORImpl< SparseMatrix< double > > >, PreconditionRelaxation< SparseMatrix< double >, internal::PreconditionRelaxation::PreconditionSORImpl< SparseMatrix< double > > >, PreconditionRelaxation< SparseMatrix< double >, internal::PreconditionRelaxation::PreconditionSSORImpl< SparseMatrix< double > > >, Quadrature< 1 >, Quadrature< dim - 1 >, Quadrature< 0 >, Quadrature< structdim >, ReadVector< VectorType::value_type >, ReadVector< VectorTraits::value_type >, ReadVector< double >, ReadVector< PetscScalar >, ReadVector< TrilinosScalar >, ReadVector< typename VectorType::value_type >, ReadVector< number >, SolverBase< Vector< double > >, SolverBase< VectorType >, SparseMatrix< double > [virtual], TableBase< 2, number >, TableBase< 2, typename MatrixType::value_type >, TableBase< 2, NumberType >, TableBase< 1, T >, TableBase< 2, T >, TableBase< 3, T >, TableBase< 4, T >, TableBase< 5, T >, TableBase< 6, T >, TableBase< 7, T >, TableBase< 2, Number >, TableBase< 2, double >, TableBase< 2, inverse_type >, TableBase< 2, InverseNumberType >, TensorFunction< rank, dim, double >, TensorFunction< 1, dim, double >, Triangulation< dim, spacedim >, Triangulation< dim, dim >, Triangulation< dimension, space_dimension >, Triangulation< 1, spacedim >, VectorMemory< Vector< double > >, VectorMemory< ::Vector< double > >, VectorMemory< BlockVector< number > >, VectorMemory< VectorType >, VectorMemory< Vector< number > >, hp::Collection< FiniteElement< dim, spacedim > >, hp::Collection< Mapping< dim, spacedim > >, hp::Collection< Quadrature< dim > >, hp::Collection< FiniteElement< dim, dim > >, hp::Collection< Mapping< dim, dim > >, hp::FEValuesBase< dim, dim - 1, ::FEFaceValues< dim, dim > >, hp::FEValuesBase< dim, dim, ::FEValues< dim, dim > >, AffineConstraints< number >, Algorithms::OperatorBase, Algorithms::OutputOperator< VectorType >, Algorithms::TimestepControl, AnyData, ArpackSolver, BlockIndices, BlockInfo, BlockMatrixBase< MatrixType >, BlockSparseMatrixEZ< Number >, CellDataStorage< CellIteratorType, DataType >, ChunkSparseMatrix< number > [virtual], ChunkSparsityPattern, DataPostprocessor< dim >, DiagonalMatrix< VectorType >, DoFHandler< dim, spacedim >, FERemoteEvaluationCommunicator< dim >, FESeries::Fourier< dim, spacedim >, FESeries::Legendre< dim, spacedim >, FETools::FEFactoryBase< dim, spacedim >, FEValuesBase< dim, spacedim >, FiniteElement< dim, spacedim >, Function< dim, RangeNumberType >, GeneralDataStorage, GridTools::Cache< dim, spacedim >, InterGridMap< MeshType >, LinearAlgebra::TpetraWrappers::PreconditionBase< Number, MemorySpace >, LinearAlgebra::TpetraWrappers::SparseMatrix< Number, MemorySpace >, LogStream, MGCoarseGridBase< VectorType >, MGConstrainedDoFs, MGLevelObject< Object >, MGMatrixBase< VectorType >, MGMatrixBlockVector< MatrixType >, MGSmootherBase< VectorType >, MGTransferBase< VectorType >, MGTwoLevelTransferBase< VectorType >, Manifold< dim, spacedim >, Mapping< dim, spacedim >, MatrixBlock< MatrixType >, MatrixFree< dim, Number, VectorizedArrayType >, MatrixFreeOperators::Base< dim, VectorType, VectorizedArrayType >, MatrixFreeOperators::MGInterfaceOperator< OperatorType >, MeshWorker::LocalIntegrator< dim, spacedim, number >, MeshWorker::VectorSelector, Multigrid< VectorType >, NonMatching::MappingInfo< dim, spacedim, Number >, NonMatching::MeshClassifier< dim >, PArpackSolver< VectorType >, PETScWrappers::MatrixBase, PETScWrappers::PreconditionBase, ParameterAcceptor, ParameterHandler, Particles::ParticleHandler< dim, spacedim >, Polynomials::PiecewisePolynomial< number >, Polynomials::Polynomial< number >, Portable::MatrixFree< dim, Number >, PreconditionBlock< MatrixType, inverse_type > [virtual], PreconditionBlockJacobi< MatrixType, inverse_type > [virtual], PreconditionBlockSOR< MatrixType, inverse_type > [virtual], PreconditionBlockSSOR< MatrixType, inverse_type > [virtual], PreconditionChebyshev< MatrixType, VectorType, PreconditionerType >, PreconditionIdentity, PreconditionLU< number >, PreconditionMG< dim, VectorType, TransferType >, PreconditionRelaxation< MatrixType, PreconditionerType >, PreconditionRichardson, PreconditionSelector< MatrixType, VectorType >, PreconditionUseMatrix< MatrixType, VectorType >, Quadrature< dim >, ReadVector< Number >, RelaxationBlock< MatrixType, InverseNumberType, VectorType >::AdditionalData, RelaxationBlockJacobi< MatrixType, InverseNumberType, VectorType > [virtual], RelaxationBlockSOR< MatrixType, InverseNumberType, VectorType > [virtual], RelaxationBlockSSOR< MatrixType, InverseNumberType, VectorType > [virtual], RepartitioningPolicyTools::Base< dim, spacedim >, SolverBase< VectorType >, SolverControl, SolverSelector< VectorType >, SparseDirectUMFPACK, SparseLUDecomposition< number > [virtual], SparseMatrix< number > [virtual], SparseMatrixEZ< number >, SparsityPatternBase, TableBase< N, T >, TensorFunction< rank, dim, Number >, TimeStepBase, Triangulation< dim, spacedim >, TrilinosWrappers::PreconditionBase, TrilinosWrappers::SolverDirect, TrilinosWrappers::SparseMatrix, VectorMemory< VectorType >, hp::Collection< T >, hp::FEValuesBase< dim, q_dim, FEValuesType >, internal::parallel::shared::TemporarilyRestoreSubdomainIds< dim, spacedim >, mg::SparseMatrixCollection< number >, and parallel::distributed::TemporarilyMatchRefineFlags< dim, spacedim >.

Public Member Functions
	EnableObserverPointer ()
	EnableObserverPointer (const EnableObserverPointer &)
	EnableObserverPointer (EnableObserverPointer &&) noexcept
virtual	~EnableObserverPointer ()
EnableObserverPointer &	operator= (const EnableObserverPointer &)
EnableObserverPointer &	operator= (EnableObserverPointer &&) noexcept
template<class Archive >
void	serialize (Archive &ar, const unsigned int version)
EnableObserverPointer functionality
Classes derived from EnableObserverPointer provide a facility to subscribe to this object. This is mostly used by the ObserverPointer class.
void	subscribe (std::atomic< bool > *const validity, const std::string &identifier="") const
void	unsubscribe (std::atomic< bool > *const validity, const std::string &identifier="") const
unsigned int	n_subscriptions () const
template<typename StreamType >
void	list_subscribers (StreamType &stream) const
void	list_subscribers () const

Static Public Member Functions
static ::ExceptionBase &	ExcInUse (int arg1, std::string arg2, std::string arg3)
static ::ExceptionBase &	ExcNoSubscriber (std::string arg1, std::string arg2)

Private Types
using	map_value_type = decltype(counter_map)::value_type
using	map_iterator = decltype(counter_map)::iterator

Private Member Functions
void	check_no_subscribers () const noexcept

Private Attributes
std::atomic< unsigned int >	counter
std::map< std::string, unsigned int >	counter_map
std::vector< std::atomic< bool > * >	validity_pointers
const std::type_info *	object_info

Static Private Attributes
static std::mutex	mutex

Detailed Description

This class supports the functioning of the ObserverPointer class.

Used as a base class, this class allows the ObserverPointer class to register with an object that it is observing that object. As a consequence, the object can report an error when its destructor is called if there are still ObserverPointers pointing to it, since destroying the object would lead to dangling pointers that point to memory that's no longer valid.

In actual practice, the mechanism works as follows: Assume you have an ObserverPointer<X> object that points objects of type X (where X is derived from EnableObserverPointer). When you write

ObserverPointer<X> ptr;
X                  object;
ptr = &x;

then ObserverPointer::operator=() called in the last line of the code above will call the EnableObserverPointer::subscribe() function (of the class documented here) with arguments that allow both sides to track each other. If object goes out of scope while ptr is still pointing to it, this would create a dangling pointer, and the destructor of X (i.e., actually the destructor of the EnableObserverPointer base class of X) will abort the program with an error.

In practice, when such an error happens, it is often difficult to tell which pointer is still pointing to the object that is being destroyed. To this end, ObserverPointer can also pass a string to the subscribe() member function that identifies which observer is still alive. This string is passed to the ObserverPointer object upon construction and is user-defined so that code developed can give names to their observer pointers.

Definition at line 66 of file enable_observer_pointer.h.

Member Typedef Documentation

map_value_type

using EnableObserverPointer::map_value_type = decltype(counter_map)::value_type

private

The data type used in counter_map.

Definition at line 238 of file enable_observer_pointer.h.

map_iterator

using EnableObserverPointer::map_iterator = decltype(counter_map)::iterator

private

The iterator type used in counter_map.

Definition at line 243 of file enable_observer_pointer.h.

Constructor & Destructor Documentation

EnableObserverPointer() [1/3]

EnableObserverPointer::EnableObserverPointer ( )

inline

Constructor setting the counter to zero.

Definition at line 297 of file enable_observer_pointer.h.

EnableObserverPointer() [2/3]

EnableObserverPointer::EnableObserverPointer ( const EnableObserverPointer &  )

inline

Copy-constructor.

The counter of the copy is zero, since references point to the original object.

Definition at line 304 of file enable_observer_pointer.h.

EnableObserverPointer() [3/3]

EnableObserverPointer::EnableObserverPointer ( EnableObserverPointer &&  subscriptor )

noexcept

Move constructor.

An object inheriting from EnableObserverPointer can only be moved if no other objects are subscribing to it.

Definition at line 32 of file enable_observer_pointer.cc.

~EnableObserverPointer()

EnableObserverPointer::~EnableObserverPointer ( )

virtual

Destructor, asserting that the counter is zero.

Definition at line 44 of file enable_observer_pointer.cc.

Member Function Documentation

operator=() [1/2]

EnableObserverPointer & EnableObserverPointer::operator= ( const EnableObserverPointer &  s )

inline

Assignment operator.

This has to be handled with care, too, because the counter has to remain the same. It therefore does nothing more than returning *this.

Definition at line 313 of file enable_observer_pointer.h.

operator=() [2/2]

EnableObserverPointer & EnableObserverPointer::operator= ( EnableObserverPointer &&  s )

noexcept

Move assignment operator. Only invalidates the object moved from.

Definition at line 119 of file enable_observer_pointer.cc.

subscribe()

void EnableObserverPointer::subscribe	(	std::atomic< bool > *const	validity,
		const std::string &	identifier = ""
	)		const

Subscribes a user of the object by storing the pointer validity. The subscriber may be identified by text supplied as identifier.

Definition at line 131 of file enable_observer_pointer.cc.

unsubscribe()

void EnableObserverPointer::unsubscribe	(	std::atomic< bool > *const	validity,
		const std::string &	identifier = ""
	)		const

Unsubscribes a user from the object.

Note

The identifier and the validity pointer must be the same as the one supplied to subscribe().

Definition at line 151 of file enable_observer_pointer.cc.

n_subscriptions()

unsigned int EnableObserverPointer::n_subscriptions ( ) const

inline

Return the present number of subscriptions to this object. This allows to use this class for reference counted lifetime determination where the last one to unsubscribe also deletes the object.

Definition at line 322 of file enable_observer_pointer.h.

list_subscribers() [1/2]

template<typename StreamType >

void EnableObserverPointer::list_subscribers ( StreamType &  stream ) const

inline

List the subscribers to the input stream.

Definition at line 339 of file enable_observer_pointer.h.

list_subscribers() [2/2]

void EnableObserverPointer::list_subscribers

(

)

const

List the subscribers to deallog.

Definition at line 199 of file enable_observer_pointer.cc.

serialize()

template<class Archive >

void EnableObserverPointer::serialize ( Archive &  ar, const unsigned int  version  )

inline

Read or write the data of this object to or from a stream for the purpose of serialization using the BOOST serialization library.

This function does not actually serialize any of the member variables of this class. The reason is that what this class stores is only who subscribes to this object, but who does so at the time of storing the contents of this object does not necessarily have anything to do with who subscribes to the object when it is restored. Consequently, we do not want to overwrite the subscribers at the time of restoring, and then there is no reason to write the subscribers out in the first place.

Definition at line 331 of file enable_observer_pointer.h.

check_no_subscribers()

void EnableObserverPointer::check_no_subscribers ( ) const

privatenoexcept

Check that there are no objects subscribing to this object. If this check passes then it is safe to destroy the current object. It this check fails then this function will either abort or print an error message to deallog (by using the AssertNothrow mechanism), but will not throw an exception.

Note

Since this function is just a consistency check it does nothing in release mode.

If this function is called when there is an uncaught exception then, rather than aborting, this function prints an error message to the standard error stream and returns.

Definition at line 53 of file enable_observer_pointer.cc.

Member Data Documentation

counter

std::atomic<unsigned int> EnableObserverPointer::counter

mutableprivate

Store the number of objects which subscribed to this object. Initially, this number is zero, and upon destruction it shall be zero again (i.e. all objects which subscribed should have unsubscribed again).

The creator (and owner) of an object is counted in the map below if HE manages to supply identification.

We use the mutable keyword in order to allow subscription to constant objects also.

This counter may be read from and written to concurrently in multithreaded code: hence we use the std::atomic class template.

Definition at line 227 of file enable_observer_pointer.h.

counter_map

std::map<std::string, unsigned int> EnableObserverPointer::counter_map

mutableprivate

In this map, we count subscriptions for each different identification string supplied to subscribe().

Definition at line 233 of file enable_observer_pointer.h.

validity_pointers

std::vector<std::atomic<bool> *> EnableObserverPointer::validity_pointers

mutableprivate

In this vector, we store pointers to the validity bool in the ObserverPointer objects that subscribe to this class.

Definition at line 249 of file enable_observer_pointer.h.

object_info

const std::type_info* EnableObserverPointer::object_info

mutableprivate

Pointer to the typeinfo object of this object, from which we can later deduce the class name. Since this information on the derived class is neither available in the destructor, nor in the constructor, we obtain it in between and store it here.

Definition at line 257 of file enable_observer_pointer.h.

mutex

std::mutex EnableObserverPointer::mutex

staticprivate

A mutex used to ensure data consistency when accessing the mutable members of this class. This lock is used in the subscribe() and unsubscribe() functions, as well as in list_subscribers().

Definition at line 280 of file enable_observer_pointer.h.

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

• include/deal.II/base/enable_observer_pointer.h
• source/base/enable_observer_pointer.cc