Reference documentation for deal.II version 8.4.1
Classes | Public Types | Public Member Functions | Private Member Functions | Private Attributes | Related Functions | List of all members
IndexSet Class Reference

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

Classes

class  ElementIterator
 
class  IntervalAccessor
 
class  IntervalIterator
 
struct  Range
 

Public Types

typedef types::global_dof_index size_type
 
typedef signed int value_type
 

Public Member Functions

 IndexSet ()
 
 IndexSet (const size_type size)
 
 IndexSet (const Epetra_Map &map)
 
void clear ()
 
void set_size (const size_type size)
 
size_type size () const
 
void add_range (const size_type begin, const size_type end)
 
void add_index (const size_type index)
 
template<typename ForwardIterator >
void add_indices (const ForwardIterator &begin, const ForwardIterator &end)
 
void add_indices (const IndexSet &other, const unsigned int offset=0)
 
bool is_element (const size_type index) const
 
bool is_contiguous () const
 
size_type n_elements () const
 
size_type nth_index_in_set (const unsigned int local_index) const
 
size_type index_within_set (const size_type global_index) const
 
unsigned int n_intervals () const
 
unsigned int largest_range_starting_index () const
 
void compress () const
 
bool operator== (const IndexSet &is) const
 
bool operator!= (const IndexSet &is) const
 
IndexSet operator& (const IndexSet &is) const
 
IndexSet get_view (const size_type begin, const size_type end) const
 
void subtract_set (const IndexSet &other)
 
void fill_index_vector (std::vector< size_type > &indices) const
 
template<typename VectorType >
void fill_binary_vector (VectorType &vector) const
 
template<class StreamType >
void print (StreamType &out) const
 
void write (std::ostream &out) const
 
void read (std::istream &in)
 
void block_write (std::ostream &out) const
 
void block_read (std::istream &in)
 
Epetra_Map make_trilinos_map (const MPI_Comm &communicator=MPI_COMM_WORLD, const bool overlapping=false) const
 
std::size_t memory_consumption () const
 
template<class Archive >
void serialize (Archive &ar, const unsigned int version)
 
Iterators
ElementIterator begin () const
 
ElementIterator end () const
 
IntervalIterator begin_intervals () const
 
IntervalIterator end_intervals () const
 

Private Member Functions

void do_compress () const
 

Private Attributes

std::vector< Rangeranges
 
bool is_compressed
 
size_type index_space_size
 
size_type largest_range
 

Related Functions

(Note that these are not member functions.)

IndexSet complete_index_set (const unsigned int N)
 

Detailed Description

A class that represents a subset of indices among a larger set. For example, it can be used to denote the set of degrees of freedom within the range \([0,\text{dof\_handler.n\_dofs})\) that belongs to a particular subdomain, or those among all degrees of freedom that are stored on a particular processor in a distributed parallel computation.

This class can represent a collection of half-open ranges of indices as well as individual elements. For practical purposes it also stores the overall range these indices can assume. In other words, you need to specify the size of the index space \([0,\text{size})\) of which objects of this class are a subset.

There are two ways to iterate over the IndexSets: First, begin() and end() allow iteration over individual indices in the set. Second, begin_interval() and end_interval() allow iteration over the half-open ranges as described above.

The data structures used in this class along with a rationale can be found in the Distributed Computing paper.

Author
Wolfgang Bangerth, 2009

Definition at line 65 of file index_set.h.

Member Typedef Documentation

size_type is the type used for storing the size and the individual entries in the IndexSet.

Definition at line 70 of file index_set.h.

typedef signed int IndexSet::value_type

One can see an IndexSet as a container of size size(), where the elements of the containers are bool values that are either false or true, depending on whether a particular index is an element of the IndexSet or not. In other words, an IndexSet is a bit like a vector in which the elements we store are booleans. In this view, the correct local typedef indicating the type of the elements of the vector would then be bool.

On the other hand, bool has the disadvantage that it is not a numerical type that, for example, allows multiplication with a double. In other words, one can not easily use a vector of booleans in a place where other vectors are allowed. Consequently, we declare the type of the elements of such a vector as a signed integer. This uses the fact that in the C++ language, booleans are implicitly convertible to integers. In other words, declaring the type of the elements of the vector as a signed integer is only a small lie, but it is a useful one.

Definition at line 95 of file index_set.h.

Constructor & Destructor Documentation

IndexSet::IndexSet ( )
inline

Default constructor.

Definition at line 1202 of file index_set.h.

IndexSet::IndexSet ( const size_type  size)
inlineexplicit

Constructor that also sets the overall size of the index range.

Definition at line 1212 of file index_set.h.

IndexSet::IndexSet ( const Epetra_Map &  map)
explicit

Constructor from a trilinos Epetra_Map.

Definition at line 61 of file index_set.cc.

Member Function Documentation

void IndexSet::clear ( )
inline

Remove all indices from this index set. The index set retains its size, however.

Definition at line 1223 of file index_set.h.

void IndexSet::set_size ( const size_type  size)
inline

Set the maximal size of the indices upon which this object operates.

This function can only be called if the index set does not yet contain any elements. This can be achieved by calling clear(), for example.

Definition at line 1234 of file index_set.h.

IndexSet::size_type IndexSet::size ( ) const
inline

Return the size of the index space of which this index set is a subset of.

Note that the result is not equal to the number of indices within this set. The latter information is returned by n_elements().

Definition at line 1247 of file index_set.h.

void IndexSet::add_range ( const size_type  begin,
const size_type  end 
)

Add the half-open range \([\text{begin},\text{end})\) to the set of indices represented by this class.

Parameters
[in]beginThe first element of the range to be added.
[in]endThe past-the-end element of the range to be added.

Definition at line 86 of file index_set.cc.

void IndexSet::add_index ( const size_type  index)
inline

Add an individual index to the set of indices.

Definition at line 1268 of file index_set.h.

template<typename ForwardIterator >
void IndexSet::add_indices ( const ForwardIterator &  begin,
const ForwardIterator &  end 
)
inline

Add a whole set of indices described by dereferencing every element of the iterator range [begin,end).

Parameters
[in]beginIterator to the first element of range of indices to be added
[in]endThe past-the-end iterator for the range of elements to be added.
Precondition
The condition begin<=end needs to be satisfied.

Definition at line 1291 of file index_set.h.

void IndexSet::add_indices ( const IndexSet other,
const unsigned int  offset = 0 
)

Add the given IndexSet other to the current one, constructing the union of *this and other.

If the offset argument is nonzero, then every index in other is shifted by offset before being added to the current index set. This allows to construct, for example, one index set from several others that are supposed to represent index sets corresponding to different ranges (e.g., when constructing the set of nonzero entries of a block vector from the sets of nonzero elements of the individual blocks of a vector).

This function will generate an exception if any of the (possibly shifted) indices of the other index set lie outside the range [0,size()) represented by the current object.

Definition at line 344 of file index_set.cc.

bool IndexSet::is_element ( const size_type  index) const
inline

Return whether the specified index is an element of the index set.

Definition at line 1317 of file index_set.h.

bool IndexSet::is_contiguous ( ) const
inline

Return whether the index set stored by this object defines a contiguous range. This is true also if no indices are stored at all.

Definition at line 1370 of file index_set.h.

IndexSet::size_type IndexSet::n_elements ( ) const
inline

Return the number of elements stored in this index set.

Definition at line 1380 of file index_set.h.

IndexSet::size_type IndexSet::nth_index_in_set ( const unsigned int  local_index) const
inline

Return the global index of the local index with number local_index stored in this index set. local_index obviously needs to be less than n_elements().

Definition at line 1432 of file index_set.h.

IndexSet::size_type IndexSet::index_within_set ( const size_type  global_index) const
inline

Return the how-manyth element of this set (counted in ascending order) global_index is. global_index needs to be less than the size(). This function throws an exception if the index global_index is not actually a member of this index set, i.e. if is_element(global_index) is false.

Definition at line 1475 of file index_set.h.

unsigned int IndexSet::n_intervals ( ) const
inline

Each index set can be represented as the union of a number of contiguous intervals of indices, where if necessary intervals may only consist of individual elements to represent isolated members of the index set.

This function returns the minimal number of such intervals that are needed to represent the index set under consideration.

Definition at line 1408 of file index_set.h.

unsigned int IndexSet::largest_range_starting_index ( ) const
inline

This function returns the local index of the beginning of the largest range.

Definition at line 1418 of file index_set.h.

void IndexSet::compress ( ) const
inline

Compress the internal representation by merging individual elements with contiguous ranges, etc. This function does not have any external effect.

Definition at line 1256 of file index_set.h.

bool IndexSet::operator== ( const IndexSet is) const
inline

Comparison for equality of index sets. This operation is only allowed if the size of the two sets is the same (though of course they do not have to have the same number of indices).

Definition at line 1517 of file index_set.h.

bool IndexSet::operator!= ( const IndexSet is) const
inline

Comparison for inequality of index sets. This operation is only allowed if the size of the two sets is the same (though of course they do not have to have the same number of indices).

Definition at line 1532 of file index_set.h.

IndexSet IndexSet::operator& ( const IndexSet is) const

Return the intersection of the current index set and the argument given, i.e. a set of indices that are elements of both index sets. The two index sets must have the same size (though of course they do not have to have the same number of indices).

Definition at line 180 of file index_set.cc.

IndexSet IndexSet::get_view ( const size_type  begin,
const size_type  end 
) const

This command takes an interval [begin, end) and returns the intersection of the current index set with the interval, shifted to the range [0, end-begin).

In other words, the result of this operation is the intersection of the set represented by the current object and the interval [begin, end), as seen within the interval [begin, end) by shifting the result of the intersection operation to the left by begin. This corresponds to the notion of a view: The interval [begin, end) is a window through which we see the set represented by the current object.

Definition at line 235 of file index_set.cc.

void IndexSet::subtract_set ( const IndexSet other)

Removes all elements contained in other from this set. In other words, if \(x\) is the current object and \(o\) the argument, then we compute \(x \leftarrow x \backslash o\).

Definition at line 269 of file index_set.cc.

void IndexSet::fill_index_vector ( std::vector< size_type > &  indices) const

Fills the given vector with all indices contained in this IndexSet.

Definition at line 461 of file index_set.cc.

template<typename VectorType >
void IndexSet::fill_binary_vector ( VectorType &  vector) const

Fill the given vector with either zero or one elements, providing a binary representation of this index set. The given vector is assumed to already have the correct size.

The given argument is filled with integer values zero and one, using vector.operator[]. Thus, any object that has such an operator can be used as long as it allows conversion of integers zero and one to elements of the vector. Specifically, this is the case for classes Vector, BlockVector, but also std::vector<bool>, std::vector<int>, and std::vector<double>.

template<class StreamType >
void IndexSet::print ( StreamType &  out) const
inline

Outputs a text representation of this IndexSet to the given stream. Used for testing.

Definition at line 1570 of file index_set.h.

void IndexSet::write ( std::ostream &  out) const

Writes the IndexSet into a text based file format, that can be read in again using the read() function.

Definition at line 394 of file index_set.cc.

void IndexSet::read ( std::istream &  in)

Constructs the IndexSet from a text based representation given by the stream in written by the write() function.

Definition at line 409 of file index_set.cc.

void IndexSet::block_write ( std::ostream &  out) const

Writes the IndexSet into a binary, compact representation, that can be read in again using the block_read() function.

Definition at line 427 of file index_set.cc.

void IndexSet::block_read ( std::istream &  in)

Constructs the IndexSet from a binary representation given by the stream in written by the write_block() function.

Definition at line 442 of file index_set.cc.

Epetra_Map IndexSet::make_trilinos_map ( const MPI_Comm &  communicator = MPI_COMM_WORLD,
const bool  overlapping = false 
) const

Given an MPI communicator, create a Trilinos map object that represents a distribution of vector elements or matrix rows in which we will locally store those elements or rows for which we store the index in the current index set, and all the other elements/rows elsewhere on one of the other MPI processes.

The last argument only plays a role if the communicator is a parallel one, distributing computations across multiple processors. In that case, if the last argument is false, then it is assumed that the index sets this function is called with on all processors are mutually exclusive but together enumerate each index exactly once. In other words, if you call this function on two processors, then the index sets this function is called with must together have all possible indices from zero to size()-1, and no index must appear in both index sets. This corresponds, for example, to the case where we want to split the elements of vectors into unique subsets to be stored on different processors – no element should be owned by more than one processor, but each element must be owned by one.

On the other hand, if the second argument is true, then the index sets can be overlapping, and they also do not need to span the whole index set. This is a useful operation if we want to create vectors that not only contain the locally owned indices, but for example also the elements that correspond to degrees of freedom located on ghost cells. Another application of this method is to select a subset of the elements of a vector, e.g. for extracting only certain solution components.

Definition at line 484 of file index_set.cc.

std::size_t IndexSet::memory_consumption ( ) const

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

Definition at line 549 of file index_set.cc.

template<class Archive >
void IndexSet::serialize ( Archive &  ar,
const unsigned int  version 
)
inline

Write or read the data of this object to or from a stream for the purpose of serialization

Definition at line 1603 of file index_set.h.

IndexSet::ElementIterator IndexSet::begin ( ) const
inline

Return an iterator that points at the first index that is contained in this IndexSet.

Definition at line 1165 of file index_set.h.

IndexSet::ElementIterator IndexSet::end ( ) const
inline

Return an iterator that points one after the last index that is contained in this IndexSet.

Definition at line 1175 of file index_set.h.

IndexSet::IntervalIterator IndexSet::begin_intervals ( ) const
inline

Return an Iterator that points at the first interval of this IndexSet.

Definition at line 1183 of file index_set.h.

IndexSet::IntervalIterator IndexSet::end_intervals ( ) const
inline

Return an Iterator that points one after the last interval of this IndexSet.

Definition at line 1193 of file index_set.h.

void IndexSet::do_compress ( ) const
private

Actually perform the compress() operation.

Definition at line 118 of file index_set.cc.

Friends And Related Function Documentation

IndexSet complete_index_set ( const unsigned int  N)
related

Create and return an index set of size \(N\) that contains every single index within this range. In essence, this function returns an index set created by

IndexSet is (N);
is.add_range(0, N);

This function exists so that one can create and initialize index sets that are complete in one step, or so one can write code like

if (my_index_set == complete_index_set(my_index_set.size())
...

Definition at line 809 of file index_set.h.

Member Data Documentation

std::vector<Range> IndexSet::ranges
mutableprivate

A set of contiguous ranges of indices that make up (part of) this index set. This variable is always kept sorted.

The variable is marked "mutable" so that it can be changed by compress(), though this of course doesn't change anything about the external representation of this index set.

Definition at line 755 of file index_set.h.

bool IndexSet::is_compressed
mutableprivate

True if compress() has been called after the last change in the set of indices.

The variable is marked "mutable" so that it can be changed by compress(), though this of course doesn't change anything about the external representation of this index set.

Definition at line 765 of file index_set.h.

size_type IndexSet::index_space_size
private

The overall size of the index range. Elements of this index set have to have a smaller number than this value.

Definition at line 771 of file index_set.h.

size_type IndexSet::largest_range
mutableprivate

This integer caches the index of the largest range in ranges. This gives O(1) access to the range with most elements, while general access costs O(log(n_ranges)). The largest range is needed for the methods is_element(), index_within_set(), nth_index_in_set. In many applications, the largest range contains most elements (the locally owned range), whereas there are only a few other elements (ghosts).

Definition at line 782 of file index_set.h.


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