Table< 1, T > Class Template Reference

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

Inheritance diagram for Table< 1, T >:

Public Types
using	size_type = typename TableBase< 1, T >::size_type
using	value_type = T

Public Member Functions
	Table ()=default
	Table (const size_type size)
template<typename InputIterator >
	Table (const size_type size, InputIterator entries, const bool C_style_indexing=true)
AlignedVector< T >::const_reference	operator[] (const size_type i) const
AlignedVector< T >::reference	operator[] (const size_type i)
AlignedVector< T >::const_reference	operator() (const size_type i) const
AlignedVector< T >::reference	operator() (const size_type i)
bool	operator== (const TableBase< N, T > &T2) const
void	reset_values ()
void	reinit (const TableIndices< N > &new_size, const bool omit_default_initialization=false)
void	clear ()
size_type	size (const unsigned int i) const
const TableIndices< N > &	size () const
size_type	n_elements () const
bool	empty () const
void	fill (InputIterator entries, const bool C_style_indexing=true)
void	fill (const T &value)
AlignedVector< T >::reference	operator() (const TableIndices< N > &indices)
AlignedVector< T >::const_reference	operator() (const TableIndices< N > &indices) const
void	replicate_across_communicator (const MPI_Comm communicator, const unsigned int root_process)
void	swap (TableBase< N, T > &v) noexcept
std::size_t	memory_consumption () const
void	serialize (Archive &ar, const unsigned int version)
Querying the observer pointers an object has.
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)

Protected Member Functions
size_type	position (const TableIndices< N > &indices) const
AlignedVector< T >::reference	el (const TableIndices< N > &indices)
AlignedVector< T >::const_reference	el (const TableIndices< N > &indices) const

Protected Attributes
AlignedVector< T >	values
TableIndices< N >	table_size

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

Private Member Functions
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
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

template<typename T>
class Table< 1, T >

A class representing a one-dimensional table, i.e. a vector-like class. The majority of the interface of this class is implemented in the TableBase base class. See there for an outline of the rationale for and interface of this class.

Definition at line 833 of file table.h.

Member Typedef Documentation

size_type

template<typename T >

using Table< 1, T >::size_type = typename TableBase<1, T>::size_type

Integer type used to count the number of elements in this container.

Definition at line 839 of file table.h.

value_type

using TableBase< N, T >::value_type = T

inherited

Definition at line 443 of file table.h.

map_value_type

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

privateinherited

The data type used in counter_map.

Definition at line 223 of file enable_observer_pointer.h.

map_iterator

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

privateinherited

The iterator type used in counter_map.

Definition at line 228 of file enable_observer_pointer.h.

Constructor & Destructor Documentation

Table() [1/3]

template<typename T >

Table< 1, T >::Table ( )

default

Default constructor. Set all dimensions to zero.

Table() [2/3]

template<typename T >

Table< 1, T >::Table ( const size_type  size )

explicit

Constructor. Pass down the given dimension to the base class.

Table() [3/3]

template<typename T >

template<typename InputIterator >

Table< 1, T >::Table	(	const size_type	size,
		InputIterator	entries,
		const bool	C_style_indexing = true
	)

Constructor. Create a table with a given size and initialize it from a set of iterators.

This function is entirely equivalent to creating a table t of the given size and then calling

t.fill (entries, C_style_indexing);

on it, using the TableBase::fill() function where the arguments are explained in more detail. The point, however, is that that is only possible if the table can be changed after running the constructor, whereas calling the current constructor allows sizing and initializing an object right away so that it can be marked const.

Using this constructor, you can do things like this:

const double values[] = { 1, 2, 3 };
const Table<1,double> t(3, entries, true);

You can also initialize a table right from a file, using input iterators:

std::ifstream input ("myfile");
const Table<1,double> t(3,
                        std::istream_iterator<double>(input),
                        true);

Parameters

size	The size of this one-dimensional table.
entries	An iterator to a set of elements from which to initialize this table. It is assumed that iterator can be incremented and dereferenced a sufficient number of times to fill this table.
C_style_indexing	If true, run over elements of the table with the last index changing fastest as we dereference subsequent elements of the input range. If false, change the first index fastest.

Member Function Documentation

operator[]() [1/2]

template<typename T >

AlignedVector< T >::const_reference Table< 1, T >::operator[]

(

const size_type

i

)

const

Access operator. Since this is a one-dimensional object, this simply accesses the requested data element. Returns a read-only reference.

operator[]() [2/2]

template<typename T >

AlignedVector< T >::reference Table< 1, T >::operator[]

(

const size_type

i

)

Access operator. Since this is a one-dimensional object, this simply accesses the requested data element. Returns a read-write reference.

operator()() [1/4]

template<typename T >

AlignedVector< T >::const_reference Table< 1, T >::operator()

(

const size_type

i

)

const

Access operator. Since this is a one-dimensional object, this simply accesses the requested data element. Returns a read-only reference.

operator()() [2/4]

template<typename T >

AlignedVector< T >::reference Table< 1, T >::operator()

(

const size_type

i

)

Access operator. Since this is a one-dimensional object, this simply accesses the requested data element. Returns a read-write reference.

operator==()

bool TableBase< N, T >::operator== ( const TableBase< N, T > &  T2 ) const

inherited

Test for equality of two tables.

reset_values()

void TableBase< N, T >::reset_values ( )

inherited

Set all entries to their default value (i.e. copy them over with default constructed objects). Do not change the size of the table, though.

reinit()

void TableBase< N, T >::reinit ( const TableIndices< N > &  new_size, const bool  omit_default_initialization = false  )

inherited

Set the dimensions of this object to the sizes given in the first argument, and allocate the required memory for table entries to accommodate these sizes. If omit_default_initialization is set to false, all elements of the table are set to a default constructed object for the element type. Otherwise the memory is left in an uninitialized or otherwise undefined state.

clear()

void TableBase< N, T >::clear ( )

inherited

Set all dimensions to zero.

size() [1/2]

size_type TableBase< N, T >::size ( const unsigned int  i ) const

inherited

Size of the table in direction i.

size() [2/2]

const TableIndices< N > & TableBase< N, T >::size ( ) const

inherited

Return the sizes of this object in each direction.

n_elements()

size_type TableBase< N, T >::n_elements ( ) const

inherited

Return the number of elements stored in this object, which is the product of the extensions in each dimension.

empty()

bool TableBase< N, T >::empty ( ) const

inherited

Return whether the object is empty, i.e. one of the directions is zero. This is equivalent to n_elements()==0.

fill() [1/2]

void TableBase< N, T >::fill ( InputIterator  entries, const bool  C_style_indexing = true  )

inherited

Fill this table (which is assumed to already have the correct size) from a source given by dereferencing the given forward iterator (which could, for example, be a pointer to the first element of an array, or an inserting std::istream_iterator). The second argument denotes whether the elements pointed to are arranged in a way that corresponds to the last index running fastest or slowest. The default is to use C-style indexing where the last index runs fastest (as opposed to Fortran-style where the first index runs fastest when traversing multidimensional arrays. For example, if you try to fill an object of type Table<2,T>, then calling this function with the default value for the second argument will result in the equivalent of doing

Table<2,T> t;
for (unsigned int i=0; i<t.size(0); ++i)
  for (unsigned int j=0; j<t.size(1); ++j)
    t[i][j] = *entries++;

On the other hand, if the second argument to this function is false, then this would result in code of the following form:

Table<2,T> t;
for (unsigned int j=0; j<t.size(1); ++j)
  for (unsigned int i=0; i<t.size(0); ++i)
    t[i][j] = *entries++;

Note the switched order in which we fill the table elements by traversing the given set of iterators.

Parameters

entries	An iterator to a set of elements from which to initialize this table. It is assumed that iterator can be incremented and dereferenced a sufficient number of times to fill this table.
C_style_indexing	If true, run over elements of the table with the last index changing fastest as we dereference subsequent elements of the input range. If false, change the first index fastest.

fill() [2/2]

void TableBase< N, T >::fill ( const T &  value )

inherited

Fill all table entries with the same value.

operator()() [3/4]

AlignedVector< T >::reference TableBase< N, T >::operator() ( const TableIndices< N > &  indices )

inherited

Return a read-write reference to the indicated element.

operator()() [4/4]

AlignedVector< T >::const_reference TableBase< N, T >::operator() ( const TableIndices< N > &  indices ) const

inherited

Return the value of the indicated element as a read-only reference.

We return the requested value as a constant reference rather than by value since this object may hold data types that may be large, and we don't know here whether copying is expensive or not.

replicate_across_communicator()

void TableBase< N, T >::replicate_across_communicator ( const MPI_Comm  communicator, const unsigned int  root_process  )

inherited

This function replicates the state found on the process indicated by root_process across all processes of the MPI communicator. The current state found on any of the processes other than root_process is lost in this process. One can imagine this operation to act like a call to Utilities::MPI::broadcast() from the root process to all other processes, though in practice the function may try to move the data into shared memory regions on each of the machines that host MPI processes and let all MPI processes on this machine then access this shared memory region instead of keeping their own copy. See the general documentation of this class for a code example.

The intent of this function is to quickly exchange large arrays from one process to others, rather than having to compute or create it on all processes. This is specifically the case for data loaded from disk – say, large data tables – that are more easily dealt with by reading once and then distributing across all processes in an MPI universe, than letting each process read the data from disk itself. Specifically, the use of shared memory regions allows for replicating the data only once per multicore machine in the MPI universe, rather than replicating data once for each MPI process. This results in large memory savings if the data is large on today's machines that can easily house several dozen MPI processes per shared memory space.

This function does not imply a model of keeping data on different processes in sync, as LinearAlgebra::distributed::Vector and other vector classes do where there exists a notion of certain elements of the vector owned by each process and possibly ghost elements that are mirrored from its owning process to other processes. Rather, the elements of the current object are simply copied to the other processes, and it is useful to think of this operation as creating a set of const TableBase objects on all processes that should not be changed any more after the replication operation, as this is the only way to ensure that the vectors remain the same on all processes. This is particularly true because of the use of shared memory regions where any modification of a vector element on one MPI process may also result in a modification of elements visible on other processes, assuming they are located within one shared memory node.

Note

The use of shared memory between MPI processes requires that the detected MPI installation supports the necessary operations. This is the case for MPI 3.0 and higher.

This function is not cheap. It needs to create sub-communicators of the provided communicator object, which is generally an expensive operation. Likewise, the generation of shared memory spaces is not a cheap operation. As a consequence, this function primarily makes sense when the goal is to share large read-only data tables among processes; examples are data tables that are loaded at start-up time and then used over the course of the run time of the program. In such cases, the start-up cost of running this function can be amortized over time, and the potential memory savings from not having to store the table on each process may be substantial on machines with large core counts on which many MPI processes run on the same machine.

This function only makes sense if the data type T is "self-contained", i.e., all of its information is stored in its member variables, and if none of the member variables are pointers to other parts of the memory. This is because if a type T does have pointers to other parts of memory, then moving T into a shared memory space does not result in the other processes having access to data that the object points to with its member variable pointers: These continue to live only on one process, and are typically in memory areas not accessible to the other processes. As a consequence, the usual use case for this function is to share arrays of simple objects such as doubles or ints.

After calling this function, objects on different MPI processes share a common state. That means that certain operations become "collective", i.e., they must be called on all participating processors at the same time. In particular, you can no longer call resize(), reserve(), or clear() on one MPI process – you have to do so on all processes at the same time, because they have to communicate for these operations. If you do not do so, you will likely get a deadlock that may be difficult to debug. By extension, this rule of only collectively resizing extends to this function itself: You can not call it twice in a row because that implies that first all but the root_process throw away their data, which is not a collective operation. Generally, these restrictions on what can and can not be done hint at the correctness of the comments above: You should treat an AlignedVector on which the current function has been called as const, on which no further operations can be performed until the destructor is called.

swap()

void TableBase< N, T >::swap ( TableBase< N, T > &  v )

noexceptinherited

Swap the contents of this table and the other table v. One could do this operation with a temporary variable and copying over the data elements, but this function is significantly more efficient since it only swaps the pointers to the data of the two vectors and therefore does not need to allocate temporary storage and move data around.

This function is analogous to the swap function of all C++ standard containers. Also, there is a global function swap(u,v) that simply calls u.swap(v), again in analogy to standard functions.

memory_consumption()

std::size_t TableBase< N, T >::memory_consumption ( ) const

inherited

Determine an estimate for the memory consumption (in bytes) of this object.

serialize()

void TableBase< N, T >::serialize ( Archive &  ar, const unsigned int  version  )

inherited

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

position()

size_type TableBase< N, T >::position ( const TableIndices< N > &  indices ) const

protectedinherited

Return the position of the indicated element within the array of elements stored one after the other. This function does no index checking.

el() [1/2]

AlignedVector< T >::reference TableBase< N, T >::el ( const TableIndices< N > &  indices )

protectedinherited

Return a read-write reference to the indicated element.

This function does no bounds checking and is only to be used internally and in functions already checked.

el() [2/2]

AlignedVector< T >::const_reference TableBase< N, T >::el ( const TableIndices< N > &  indices ) const

protectedinherited

Return the value of the indicated element as a read-only reference.

This function does no bounds checking and is only to be used internally and in functions already checked.

We return the requested value as a constant reference rather than by value since this object may hold data types that may be large, and we don't know here whether copying is expensive or not.

n_subscriptions()

unsigned int EnableObserverPointer::n_subscriptions ( ) const

inlineinherited

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 339 of file enable_observer_pointer.h.

list_subscribers() [1/2]

template<typename StreamType >

void EnableObserverPointer::list_subscribers ( StreamType &  stream ) const

inlineinherited

List the subscribers to the input stream.

Definition at line 356 of file enable_observer_pointer.h.

list_subscribers() [2/2]

void EnableObserverPointer::list_subscribers ( ) const

inherited

List the subscribers to deallog.

Definition at line 199 of file enable_observer_pointer.cc.

subscribe()

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

privateinherited

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

privateinherited

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.

check_no_subscribers()

void EnableObserverPointer::check_no_subscribers ( ) const

privatenoexceptinherited

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

values

AlignedVector<T> TableBase< N, T >::values

protectedinherited

Component-array.

Definition at line 795 of file table.h.

table_size

TableIndices<N> TableBase< N, T >::table_size

protectedinherited

Size in each direction of the table.

Definition at line 800 of file table.h.

counter

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

mutableprivateinherited

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 212 of file enable_observer_pointer.h.

counter_map

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

mutableprivateinherited

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

Definition at line 218 of file enable_observer_pointer.h.

validity_pointers

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

mutableprivateinherited

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

Definition at line 234 of file enable_observer_pointer.h.

object_info

const std::type_info* EnableObserverPointer::object_info

mutableprivateinherited

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 242 of file enable_observer_pointer.h.

mutex

std::mutex EnableObserverPointer::mutex

staticprivateinherited

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 249 of file enable_observer_pointer.h.

---

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

• include/deal.II/base/table.h