SparsityPatternIterators::Iterator Class Reference

#include <deal.II/lac/sparsity_pattern.h>

Public Member Functions
	Iterator (const SparsityPattern *sp, const std::size_t index_within_sparsity)
Iterator &	operator++ ()
Iterator	operator++ (int)
const Accessor &	operator* () const
const Accessor *	operator-> () const
bool	operator== (const Iterator &) const
bool	operator!= (const Iterator &) const
bool	operator< (const Iterator &) const
int	operator- (const Iterator &p) const

Private Attributes
Accessor	accessor

Detailed Description

An iterator class for walking over the elements of a sparsity pattern.

The typical use for these iterators is to iterate over the elements of a sparsity pattern (or, since they also serve as the basis for iterating over the elements of an associated matrix, over the elements of a sparse matrix), or over the elements of individual rows. There is no guarantee that the elements of a row are actually traversed in an order in which column numbers monotonically increase. See the documentation of the SparsityPattern class for more information.

Note

This class operates directly on the internal data structures of the SparsityPattern class. As a consequence, some operations are cheap and some are not. In particular, it is cheap to access the column index of the sparsity pattern entry pointed to. On the other hand, it is expensive to access the row index (this requires \(O(\log(N))\) operations for a matrix with \(N\) row). As a consequence, when you design algorithms that use these iterators, it is common practice to not loop over all elements of a sparsity pattern at once, but to have an outer loop over all rows and within this loop iterate over the elements of this row. This way, you only ever need to dereference the iterator to obtain the column indices whereas the (expensive) lookup of the row index can be avoided by using the loop index instead.

Definition at line 238 of file sparsity_pattern.h.

Constructor & Destructor Documentation

Iterator()

SparsityPatternIterators::Iterator::Iterator	(	const SparsityPattern *	sp,
		const std::size_t	index_within_sparsity
	)

Constructor. Create an iterator into the sparsity pattern sp for the given global index (i.e., the index of the given element counting from the zeroth row).

Member Function Documentation

operator++() [1/2]

Iterator& SparsityPatternIterators::Iterator::operator++

(

)

Prefix increment.

operator++() [2/2]

Iterator SparsityPatternIterators::Iterator::operator++

(

int

)

Postfix increment.

operator*()

const Accessor& SparsityPatternIterators::Iterator::operator*

(

)

const

Dereferencing operator.

operator->()

const Accessor* SparsityPatternIterators::Iterator::operator->

(

)

const

Dereferencing operator.

operator==()

bool SparsityPatternIterators::Iterator::operator==

(

const Iterator &

)

const

Comparison. True, if both iterators point to the same matrix position.

operator!=()

bool SparsityPatternIterators::Iterator::operator!=

(

const Iterator &

)

const

Inverse of ==.

operator<()

bool SparsityPatternIterators::Iterator::operator<

(

const Iterator &

)

const

Comparison operator. Result is true if either the first row number is smaller or if the row numbers are equal and the first index is smaller.

This function is only valid if both iterators point into the same matrix.

operator-()

int SparsityPatternIterators::Iterator::operator-

(

const Iterator &

p

)

const

Return the distance between the current iterator and the argument. The distance is given by how many times one has to apply operator++ to the current iterator to get the argument (for a positive return value), or operator-- (for a negative return value).

Member Data Documentation

accessor

Accessor SparsityPatternIterators::Iterator::accessor

private

Store an object of the accessor class.

Definition at line 300 of file sparsity_pattern.h.

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

• deal.II/lac/sparsity_pattern.h