cv::SparseMat Class Reference

The class SparseMat represents multi-dimensional sparse numerical arrays. More...

#include <mat.hpp>

Inheritance diagram for cv::SparseMat:

Classes
struct	Hdr
	the sparse matrix header More...
struct	Node
	sparse matrix node - element of a hash table More...

Public Types
enum	{ MAGIC_VAL =0x42FD0000 , MAX_DIM =32 , HASH_SCALE =0x5bd1e995 , HASH_BIT =0x80000000 }
typedef SparseMatIterator	iterator
typedef SparseMatConstIterator	const_iterator

Public Member Functions
	SparseMat ()
	Various SparseMat constructors. More...
	SparseMat (int dims, const int *_sizes, int _type)
	SparseMat (const SparseMat &m)
	SparseMat (const Mat &m)
	~SparseMat ()
	the destructor More...
SparseMat &	operator= (const SparseMat &m)
	assignment operator. This is O(1) operation, i.e. no data is copied More...
SparseMat &	operator= (const Mat &m)
	equivalent to the corresponding constructor More...
CV_NODISCARD_STD SparseMat	clone () const
	creates full copy of the matrix More...
void	copyTo (SparseMat &m) const
	copies all the data to the destination matrix. All the previous content of m is erased More...
void	copyTo (Mat &m) const
	converts sparse matrix to dense matrix. More...
void	convertTo (SparseMat &m, int rtype, double alpha=1) const
	multiplies all the matrix elements by the specified scale factor alpha and converts the results to the specified data type More...
void	convertTo (Mat &m, int rtype, double alpha=1, double beta=0) const
	converts sparse matrix to dense n-dim matrix with optional type conversion and scaling. More...
void	assignTo (SparseMat &m, int type=-1) const
void	create (int dims, const int *_sizes, int _type)
	reallocates sparse matrix. More...
void	clear ()
	sets all the sparse matrix elements to 0, which means clearing the hash table. More...
void	addref ()
	manually increments the reference counter to the header. More...
void	release ()
size_t	elemSize () const
	converts sparse matrix to the old-style representation; all the elements are copied. More...
size_t	elemSize1 () const
	returns elemSize()/channels() More...
int	type () const
	returns type of sparse matrix elements More...
int	depth () const
	returns the depth of sparse matrix elements More...
int	channels () const
	returns the number of channels More...
const int *	size () const
	returns the array of sizes, or NULL if the matrix is not allocated More...
int	size (int i) const
	returns the size of i-th matrix dimension (or 0) More...
int	dims () const
	returns the matrix dimensionality More...
size_t	nzcount () const
	returns the number of non-zero elements (=the number of hash table nodes) More...
size_t	hash (int i0) const
	computes the element hash value (1D case) More...
size_t	hash (int i0, int i1) const
	computes the element hash value (2D case) More...
size_t	hash (int i0, int i1, int i2) const
	computes the element hash value (3D case) More...
size_t	hash (const int *idx) const
	computes the element hash value (nD case) More...
void	erase (int i0, int i1, size_t *hashval=0)
	erases the specified element (2D case) More...
void	erase (int i0, int i1, int i2, size_t *hashval=0)
	erases the specified element (3D case) More...
void	erase (const int *idx, size_t *hashval=0)
	erases the specified element (nD case) More...
SparseMatIterator	end ()
	returns the sparse matrix iterator at the matrix end More...
SparseMatConstIterator	end () const
	returns the read-only sparse matrix iterator at the matrix end More...
template<typename _Tp >
SparseMatIterator_< _Tp >	end ()
	returns the typed sparse matrix iterator at the matrix end More...
template<typename _Tp >
SparseMatConstIterator_< _Tp >	end () const
	returns the typed read-only sparse matrix iterator at the matrix end More...
template<typename _Tp >
_Tp &	value (Node *n)
	returns the value stored in the sparse martix node More...
template<typename _Tp >
const _Tp &	value (const Node *n) const
	returns the value stored in the sparse martix node More...
Node *	node (size_t nidx)
const Node *	node (size_t nidx) const
uchar *	newNode (const int *idx, size_t hashval)
void	removeNode (size_t hidx, size_t nidx, size_t previdx)
void	resizeHashTab (size_t newsize)
uchar *	ptr (int i0, bool createMissing, size_t *hashval=0)
	returns pointer to the specified element (1D case) More...
uchar *	ptr (int i0, int i1, bool createMissing, size_t *hashval=0)
	returns pointer to the specified element (2D case) More...
uchar *	ptr (int i0, int i1, int i2, bool createMissing, size_t *hashval=0)
	returns pointer to the specified element (3D case) More...
uchar *	ptr (const int *idx, bool createMissing, size_t *hashval=0)
	returns pointer to the specified element (nD case) More...
template<typename _Tp >
_Tp &	ref (int i0, size_t *hashval=0)
	returns reference to the specified element (1D case) More...
template<typename _Tp >
_Tp &	ref (int i0, int i1, size_t *hashval=0)
	returns reference to the specified element (2D case) More...
template<typename _Tp >
_Tp &	ref (int i0, int i1, int i2, size_t *hashval=0)
	returns reference to the specified element (3D case) More...
template<typename _Tp >
_Tp &	ref (const int *idx, size_t *hashval=0)
	returns reference to the specified element (nD case) More...
template<typename _Tp >
_Tp	value (int i0, size_t *hashval=0) const
	returns value of the specified element (1D case) More...
template<typename _Tp >
_Tp	value (int i0, int i1, size_t *hashval=0) const
	returns value of the specified element (2D case) More...
template<typename _Tp >
_Tp	value (int i0, int i1, int i2, size_t *hashval=0) const
	returns value of the specified element (3D case) More...
template<typename _Tp >
_Tp	value (const int *idx, size_t *hashval=0) const
	returns value of the specified element (nD case) More...
template<typename _Tp >
const _Tp *	find (int i0, size_t *hashval=0) const
	returns pointer to the specified element (1D case) More...
template<typename _Tp >
const _Tp *	find (int i0, int i1, size_t *hashval=0) const
	returns pointer to the specified element (2D case) More...
template<typename _Tp >
const _Tp *	find (int i0, int i1, int i2, size_t *hashval=0) const
	returns pointer to the specified element (3D case) More...
template<typename _Tp >
const _Tp *	find (const int *idx, size_t *hashval=0) const
	returns pointer to the specified element (nD case) More...
SparseMatIterator	begin ()
	returns the sparse matrix iterator at the matrix beginning More...
template<typename _Tp >
SparseMatIterator_< _Tp >	begin ()
	returns the sparse matrix iterator at the matrix beginning More...
SparseMatConstIterator	begin () const
	returns the read-only sparse matrix iterator at the matrix beginning More...
template<typename _Tp >
SparseMatConstIterator_< _Tp >	begin () const
	returns the read-only sparse matrix iterator at the matrix beginning More...

Public Attributes
int	flags
Hdr *	hdr

Detailed Description

The class SparseMat represents multi-dimensional sparse numerical arrays.

Such a sparse array can store elements of any type that Mat can store. Sparse means that only non-zero elements are stored (though, as a result of operations on a sparse matrix, some of its stored elements can actually become 0. It is up to you to detect such elements and delete them using SparseMat::erase ). The non-zero elements are stored in a hash table that grows when it is filled so that the search time is O(1) in average (regardless of whether element is there or not). Elements can be accessed using the following methods:

• Query operations (SparseMat::ptr and the higher-level SparseMat::ref, SparseMat::value and SparseMat::find), for example:

  const int dims = 5;
  int size[5] = {10, 10, 10, 10, 10};
  SparseMat sparse_mat(dims, size, CV_32F);
  for(int i = 0; i < 1000; i++)
  {
      int idx[dims];
      for(int k = 0; k < dims; k++)
          idx[k] = rand() % size[k];
      sparse_mat.ref<float>(idx) += 1.f;
  }
  cout << "nnz = " << sparse_mat.nzcount() << endl;

• Sparse matrix iterators. They are similar to MatIterator but different from NAryMatIterator. That is, the iteration loop is familiar to STL users:

  // prints elements of a sparse floating-point matrix
  // and the sum of elements.
  SparseMatConstIterator_<float>
      it = sparse_mat.begin<float>(),
      it_end = sparse_mat.end<float>();
  double s = 0;
  int dims = sparse_mat.dims();
  for(; it != it_end; ++it)
  {
      // print element indices and the element value
      const SparseMat::Node* n = it.node();
      printf("(");
      for(int i = 0; i < dims; i++)
          printf("%d%s", n->idx[i], i < dims-1 ? ", " : ")");
      printf(": %g\n", it.value<float>());
      s += *it;
  }
  printf("Element sum is %g\n", s);

  If you run this loop, you will notice that elements are not enumerated in a logical order (lexicographical, and so on). They come in the same order as they are stored in the hash table (semi-randomly). You may collect pointers to the nodes and sort them to get the proper ordering. Note, however, that pointers to the nodes may become invalid when you add more elements to the matrix. This may happen due to possible buffer reallocation.
• Combination of the above 2 methods when you need to process 2 or more sparse matrices simultaneously. For example, this is how you can compute unnormalized cross-correlation of the 2 floating-point sparse matrices:

  double cross_corr(const SparseMat& a, const SparseMat& b)
  {
      const SparseMat *_a = &a, *_b = &b;
      // if b contains less elements than a,
      // it is faster to iterate through b
      if(_a->nzcount() > _b->nzcount())
          std::swap(_a, _b);
      SparseMatConstIterator_<float> it = _a->begin<float>(),
                                     it_end = _a->end<float>();
      double ccorr = 0;
      for(; it != it_end; ++it)
      {
          // take the next element from the first matrix
          float avalue = *it;
          const Node* anode = it.node();
          // and try to find an element with the same index in the second matrix.
          // since the hash value depends only on the element index,
          // reuse the hash value stored in the node
          float bvalue = _b->value<float>(anode->idx,&anode->hashval);
          ccorr += avalue*bvalue;
      }
      return ccorr;
  }

Member Typedef Documentation

const_iterator

typedef SparseMatConstIterator cv::SparseMat::const_iterator

iterator

typedef SparseMatIterator cv::SparseMat::iterator

Member Enumeration Documentation

anonymous enum

anonymous enum

Enumerator
MAGIC_VAL
MAX_DIM
HASH_SCALE
HASH_BIT

Constructor & Destructor Documentation

SparseMat() [1/4]

cv::SparseMat::SparseMat

(

)

Various SparseMat constructors.

SparseMat() [2/4]

cv::SparseMat::SparseMat	(	int	dims,
		const int *	_sizes,
		int	_type
	)

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Parameters

dims	Array dimensionality.
_sizes	Sparce matrix size on all dementions.
_type	Sparse matrix data type.

SparseMat() [3/4]

cv::SparseMat::SparseMat

(

const SparseMat &

m

)

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Parameters

m	Source matrix for copy constructor. If m is dense matrix (ocvMat) then it will be converted to sparse representation.

SparseMat() [4/4]

cv::SparseMat::SparseMat ( const Mat &  m )

explicit

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Parameters

m	Source matrix for copy constructor. If m is dense matrix (ocvMat) then it will be converted to sparse representation.

~SparseMat()

cv::SparseMat::~SparseMat

(

)

the destructor

Member Function Documentation

addref()

void cv::SparseMat::addref

(

)

manually increments the reference counter to the header.

assignTo()

void cv::SparseMat::assignTo	(	SparseMat &	m,
		int	type = -1
	)		const

begin() [1/4]

SparseMatIterator cv::SparseMat::begin

(

)

returns the sparse matrix iterator at the matrix beginning

return the sparse matrix iterator pointing to the first sparse matrix element

begin() [2/4]

template<typename _Tp >

SparseMatIterator_<_Tp> cv::SparseMat::begin

(

)

returns the sparse matrix iterator at the matrix beginning

begin() [3/4]

SparseMatConstIterator cv::SparseMat::begin

(

)

const

returns the read-only sparse matrix iterator at the matrix beginning

begin() [4/4]

template<typename _Tp >

SparseMatConstIterator_<_Tp> cv::SparseMat::begin

(

)

const

returns the read-only sparse matrix iterator at the matrix beginning

channels()

int cv::SparseMat::channels

(

)

const

returns the number of channels

clear()

void cv::SparseMat::clear

(

)

sets all the sparse matrix elements to 0, which means clearing the hash table.

clone()

CV_NODISCARD_STD SparseMat cv::SparseMat::clone

(

)

const

creates full copy of the matrix

convertTo() [1/2]

void cv::SparseMat::convertTo	(	Mat &	m,
		int	rtype,
		double	alpha = 1,
		double	beta = 0
	)		const

converts sparse matrix to dense n-dim matrix with optional type conversion and scaling.

Parameters

[out]	m	- output matrix; if it does not have a proper size or type before the operation, it is reallocated
[in]	rtype	- desired output matrix type or, rather, the depth since the number of channels are the same as the input has; if rtype is negative, the output matrix will have the same type as the input.
[in]	alpha	- optional scale factor
[in]	beta	- optional delta added to the scaled values

convertTo() [2/2]

void cv::SparseMat::convertTo	(	SparseMat &	m,
		int	rtype,
		double	alpha = 1
	)		const

multiplies all the matrix elements by the specified scale factor alpha and converts the results to the specified data type

copyTo() [1/2]

void cv::SparseMat::copyTo

(

Mat &

m

)

const

converts sparse matrix to dense matrix.

copyTo() [2/2]

void cv::SparseMat::copyTo

(

SparseMat &

m

)

const

copies all the data to the destination matrix. All the previous content of m is erased

create()

void cv::SparseMat::create	(	int	dims,
		const int *	_sizes,
		int	_type
	)

reallocates sparse matrix.

If the matrix already had the proper size and type, it is simply cleared with clear(), otherwise, the old matrix is released (using release()) and the new one is allocated.

depth()

int cv::SparseMat::depth

(

)

const

returns the depth of sparse matrix elements

dims()

int cv::SparseMat::dims

(

)

const

returns the matrix dimensionality

elemSize()

size_t cv::SparseMat::elemSize

(

)

const

converts sparse matrix to the old-style representation; all the elements are copied.

returns the size of each element in bytes (not including the overhead - the space occupied by SparseMat::Node elements)

elemSize1()

size_t cv::SparseMat::elemSize1

(

)

const

returns elemSize()/channels()

end() [1/4]

SparseMatIterator cv::SparseMat::end

(

)

returns the sparse matrix iterator at the matrix end

return the sparse matrix iterator pointing to the element following the last sparse matrix element

end() [2/4]

template<typename _Tp >

SparseMatIterator_<_Tp> cv::SparseMat::end

(

)

returns the typed sparse matrix iterator at the matrix end

end() [3/4]

SparseMatConstIterator cv::SparseMat::end

(

)

const

returns the read-only sparse matrix iterator at the matrix end

end() [4/4]

template<typename _Tp >

SparseMatConstIterator_<_Tp> cv::SparseMat::end

(

)

const

returns the typed read-only sparse matrix iterator at the matrix end

erase() [1/3]

void cv::SparseMat::erase	(	const int *	idx,
		size_t *	hashval = 0
	)

erases the specified element (nD case)

erase() [2/3]

void cv::SparseMat::erase	(	int	i0,
		int	i1,
		int	i2,
		size_t *	hashval = 0
	)

erases the specified element (3D case)

erase() [3/3]

void cv::SparseMat::erase	(	int	i0,
		int	i1,
		size_t *	hashval = 0
	)

erases the specified element (2D case)

find() [1/4]

template<typename _Tp >

const _Tp* cv::SparseMat::find	(	const int *	idx,
		size_t *	hashval = 0
	)		const

returns pointer to the specified element (nD case)

find() [2/4]

template<typename _Tp >

const _Tp* cv::SparseMat::find	(	int	i0,
		int	i1,
		int	i2,
		size_t *	hashval = 0
	)		const

returns pointer to the specified element (3D case)

find() [3/4]

template<typename _Tp >

const _Tp* cv::SparseMat::find	(	int	i0,
		int	i1,
		size_t *	hashval = 0
	)		const

returns pointer to the specified element (2D case)

find() [4/4]

template<typename _Tp >

const _Tp* cv::SparseMat::find	(	int	i0,
		size_t *	hashval = 0
	)		const

returns pointer to the specified element (1D case)

Return pointer to the specified sparse matrix element if it exists

find<_Tp>(i0,...[,hashval]) is equivalent to (_const Tp*)ptr(i0,...false[,hashval]).

If the specified element does not exist, the methods return NULL.

hash() [1/4]

size_t cv::SparseMat::hash

(

const int *

idx

)

const

computes the element hash value (nD case)

hash() [2/4]

size_t cv::SparseMat::hash

(

int

i0

)

const

computes the element hash value (1D case)

hash() [3/4]

size_t cv::SparseMat::hash	(	int	i0,
		int	i1
	)		const

computes the element hash value (2D case)

hash() [4/4]

size_t cv::SparseMat::hash	(	int	i0,
		int	i1,
		int	i2
	)		const

computes the element hash value (3D case)

newNode()

uchar* cv::SparseMat::newNode	(	const int *	idx,
		size_t	hashval
	)

node() [1/2]

Node* cv::SparseMat::node

(

size_t

nidx

)

node() [2/2]

const Node* cv::SparseMat::node

(

size_t

nidx

)

const

nzcount()

size_t cv::SparseMat::nzcount

(

)

const

returns the number of non-zero elements (=the number of hash table nodes)

operator=() [1/2]

SparseMat& cv::SparseMat::operator=

(

const Mat &

m

)

equivalent to the corresponding constructor

operator=() [2/2]

SparseMat& cv::SparseMat::operator=

(

const SparseMat &

m

)

assignment operator. This is O(1) operation, i.e. no data is copied

ptr() [1/4]

uchar* cv::SparseMat::ptr	(	const int *	idx,
		bool	createMissing,
		size_t *	hashval = 0
	)

returns pointer to the specified element (nD case)

ptr() [2/4]

uchar* cv::SparseMat::ptr	(	int	i0,
		bool	createMissing,
		size_t *	hashval = 0
	)

returns pointer to the specified element (1D case)

specialized variants for 1D, 2D, 3D cases and the generic_type one for n-D case. return pointer to the matrix element.

• if the element is there (it's non-zero), the pointer to it is returned
• if it's not there and createMissing=false, NULL pointer is returned
• if it's not there and createMissing=true, then the new element is created and initialized with 0. Pointer to it is returned
• if the optional hashval pointer is not NULL, the element hash value is not computed, but *hashval is taken instead.

ptr() [3/4]

uchar* cv::SparseMat::ptr	(	int	i0,
		int	i1,
		bool	createMissing,
		size_t *	hashval = 0
	)

returns pointer to the specified element (2D case)

ptr() [4/4]

uchar* cv::SparseMat::ptr	(	int	i0,
		int	i1,
		int	i2,
		bool	createMissing,
		size_t *	hashval = 0
	)

returns pointer to the specified element (3D case)

ref() [1/4]

template<typename _Tp >

_Tp& cv::SparseMat::ref	(	const int *	idx,
		size_t *	hashval = 0
	)

returns reference to the specified element (nD case)

ref() [2/4]

template<typename _Tp >

_Tp& cv::SparseMat::ref	(	int	i0,
		int	i1,
		int	i2,
		size_t *	hashval = 0
	)

returns reference to the specified element (3D case)

ref() [3/4]

template<typename _Tp >

_Tp& cv::SparseMat::ref	(	int	i0,
		int	i1,
		size_t *	hashval = 0
	)

returns reference to the specified element (2D case)

ref() [4/4]

template<typename _Tp >

_Tp& cv::SparseMat::ref	(	int	i0,
		size_t *	hashval = 0
	)

returns reference to the specified element (1D case)

return read-write reference to the specified sparse matrix element.

ref<_Tp>(i0,...[,hashval]) is equivalent to *(_Tp*)ptr(i0,...,true[,hashval]). The methods always return a valid reference. If the element did not exist, it is created and initialized with 0.

release()

void cv::SparseMat::release

(

)

removeNode()

void cv::SparseMat::removeNode	(	size_t	hidx,
		size_t	nidx,
		size_t	previdx
	)

resizeHashTab()

void cv::SparseMat::resizeHashTab

(

size_t

newsize

)

size() [1/2]

const int* cv::SparseMat::size

(

)

const

returns the array of sizes, or NULL if the matrix is not allocated

size() [2/2]

int cv::SparseMat::size

(

int

i

)

const

returns the size of i-th matrix dimension (or 0)

type()

int cv::SparseMat::type

(

)

const

returns type of sparse matrix elements

value() [1/6]

template<typename _Tp >

_Tp cv::SparseMat::value	(	const int *	idx,
		size_t *	hashval = 0
	)		const

returns value of the specified element (nD case)

value() [2/6]

template<typename _Tp >

const _Tp& cv::SparseMat::value

(

const Node *

n

)

const

returns the value stored in the sparse martix node

value() [3/6]

template<typename _Tp >

_Tp cv::SparseMat::value	(	int	i0,
		int	i1,
		int	i2,
		size_t *	hashval = 0
	)		const

returns value of the specified element (3D case)

value() [4/6]

template<typename _Tp >

_Tp cv::SparseMat::value	(	int	i0,
		int	i1,
		size_t *	hashval = 0
	)		const

returns value of the specified element (2D case)

value() [5/6]

template<typename _Tp >

_Tp cv::SparseMat::value	(	int	i0,
		size_t *	hashval = 0
	)		const

returns value of the specified element (1D case)

return value of the specified sparse matrix element.

value<_Tp>(i0,...[,hashval]) is equivalent to

{ const _Tp* p = find<_Tp>(i0,...[,hashval]); return p ? *p : _Tp(); }

That is, if the element did not exist, the methods return 0.

value() [6/6]

template<typename _Tp >

_Tp& cv::SparseMat::value

(

Node *

n

)

returns the value stored in the sparse martix node

Member Data Documentation

flags

int cv::SparseMat::flags

hdr

Hdr* cv::SparseMat::hdr

---

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

• build/release/_deps/opencv-src/include/opencv4/opencv2/core/mat.hpp