cern.colt.matrix.tdouble.impl
Class SparseDoubleMatrix2D

java.lang.Object
  cern.colt.PersistentObject
      cern.colt.matrix.AbstractMatrix
          cern.colt.matrix.AbstractMatrix2D
              cern.colt.matrix.tdouble.DoubleMatrix2D
                  cern.colt.matrix.tdouble.impl.SparseDoubleMatrix2D

All Implemented Interfaces:

Serializable, Cloneable

public class SparseDoubleMatrix2D
extends DoubleMatrix2D

Sparse hashed 2-d matrix holding double elements. First see the package summary and javadoc tree view to get the broad picture.

Implementation:

Note that this implementation is not synchronized. Uses a OpenIntDoubleHashMap, which is a compact and performant hashing technique.

Memory requirements:

Cells that

• are never set to non-zero values do not use any memory.
• switch from zero to non-zero state do use memory.
• switch back from non-zero to zero state also do use memory. However, their memory is automatically reclaimed from time to time. It can also manually be reclaimed by calling trimToSize().

worst case: memory [bytes] = (1/minLoadFactor) * nonZeros * 13.
best case: memory [bytes] = (1/maxLoadFactor) * nonZeros * 13.
Where nonZeros = cardinality() is the number of non-zero cells. Thus, a 1000 x 1000 matrix with minLoadFactor=0.25 and maxLoadFactor=0.5 and 1000000 non-zero cells consumes between 25 MB and 50 MB. The same 1000 x 1000 matrix with 1000 non-zero cells consumes between 25 and 50 KB.

Time complexity:

This class offers expected time complexity O(1) (i.e. constant time) for the basic operations get, getQuick, set, setQuick and size assuming the hash function disperses the elements properly among the buckets. Otherwise, pathological cases, although highly improbable, can occur, degrading performance to O(N) in the worst case. As such this sparse class is expected to have no worse time complexity than its dense counterpart DenseDoubleMatrix2D. However, constant factors are considerably larger.

Cells are internally addressed in row-major. Performance sensitive applications can exploit this fact. Setting values in a loop row-by-row is quicker than column-by-column, because fewer hash collisions occur. Thus

 for (int row = 0; row < rows; row++) {
     for (int column = 0; column < columns; column++) {
         matrix.setQuick(row, column, someValue);
     }
 }
 

is quicker than

 for (int column = 0; column < columns; column++) {
     for (int row = 0; row < rows; row++) {
         matrix.setQuick(row, column, someValue);
     }
 }
 

Version:

1.0, 09/24/99, 1.1, 08/22/2007

Author:

wolfgang.hoschek@cern.ch, Piotr Wendykier (piotr.wendykier@gmail.com)

See Also:

cern.colt.map, OpenIntDoubleHashMap, Serialized Form

Field Summary

Fields inherited from class cern.colt.PersistentObject

serialVersionUID

Constructor Summary

SparseDoubleMatrix2D(double[][] values)
Constructs a matrix with a copy of the given values.

SparseDoubleMatrix2D(int rows, int columns)
Constructs a matrix with a given number of rows and columns and default memory usage.

SparseDoubleMatrix2D(int rows, int columns, int initialCapacity, double minLoadFactor, double maxLoadFactor)
Constructs a matrix with a given number of rows and columns using memory as specified.

Method Summary

DoubleMatrix2D	assign(double value) Sets all cells to the state specified by value.
DoubleMatrix2D	assign(DoubleFunction function) Assigns the result of a function to each cell; x[row,col] = function(x[row,col]).
DoubleMatrix2D	assign(DoubleMatrix2D source) Replaces all cell values of the receiver with the values of another matrix.
DoubleMatrix2D	assign(DoubleMatrix2D y, DoubleDoubleFunction function) Assigns the result of a function to each cell; x[row,col] = function(x[row,col],y[row,col]).
int	cardinality() Returns the number of cells having non-zero values.
void	dct2(boolean scale) Computes the 2D discrete cosine transform (DCT-II) of this matrix.
void	dctColumns(boolean scale) Computes the discrete cosine transform (DCT-II) of each column of this matrix.
void	dctRows(boolean scale) Computes the discrete cosine transform (DCT-II) of each row of this matrix.
void	dht2() Computes the 2D discrete Hartley transform (DHT) of this matrix.
void	dhtColumns() Computes the discrete Hartley transform (DHT) of each column of this matrix.
void	dhtRows() Computes the discrete Hartley transform (DHT) of each row of this matrix.
void	dst2(boolean scale) Computes the 2D discrete sine transform (DST-II) of this matrix.
void	dstColumns(boolean scale) Computes the discrete sine transform (DST-II) of each column of this matrix.
void	dstRows(boolean scale) Computes the discrete sine transform (DST-II) of each row of this matrix.
AbstractIntDoubleMap	elements() Returns the elements of this matrix.
void	ensureCapacity(int minCapacity) Ensures that the receiver can hold at least the specified number of non-zero cells without needing to allocate new internal memory.
void	fft2() Computes the 2D discrete Fourier transform (DFT) of this matrix.
DoubleMatrix2D	forEachNonZero(IntIntDoubleFunction function) Assigns the result of a function to each non-zero cell; x[row,col] = function(x[row,col]).
DComplexMatrix2D	getFft2() Returns new complex matrix which is the 2D discrete Fourier transform (DFT) of this matrix.
DComplexMatrix2D	getFftColumns() Returns new complex matrix which is the discrete Fourier transform (DFT) of each column of this matrix.
DComplexMatrix2D	getFftRows() Returns new complex matrix which is the discrete Fourier transform (DFT) of each row of this matrix.
DComplexMatrix2D	getIfft2(boolean scale) Returns new complex matrix which is the 2D inverse of the discrete Fourier transform (IDFT) of this matrix.
DComplexMatrix2D	getIfftColumns(boolean scale) Returns new complex matrix which is the inverse of the discrete Fourier transform (IDFT) of each column of this matrix.
DComplexMatrix2D	getIfftRows(boolean scale) Returns new complex matrix which is the inverse of the discrete Fourier transform (IDFT) of each row of this matrix.
double	getQuick(int row, int column) Returns the matrix cell value at coordinate [row,column].
void	idct2(boolean scale) Computes the 2D inverse of the discrete cosine transform (DCT-III) of this matrix.
void	idctColumns(boolean scale) Computes the inverse of the discrete cosine transform (DCT-III) of each column of this matrix.
void	idctRows(boolean scale) Computes the inverse of the discrete cosine transform (DCT-III) of each row of this matrix.
void	idht2(boolean scale) Computes the 2D inverse of the discrete Hartley transform (IDHT) of this matrix.
void	idhtColumns(boolean scale) Computes the inverse of the discrete Hartley transform (IDHT) of each column of this matrix.
void	idhtRows(boolean scale) Computes the inverse of the discrete Hartley transform (IDHT) of each row of this matrix.
void	idst2(boolean scale) Computes the 2D inverse of the discrete sine transform (DST-III) of this matrix.
void	idstColumns(boolean scale) Computes the inverse of the discrete sine transform (DST-III) of each column of this matrix.
void	idstRows(boolean scale) Computes the inverse of the discrete sine transform (DST-III) of each row of this matrix.
void	ifft2(boolean scale) Computes the 2D inverse of the discrete Fourier transform (IDFT) of this matrix.
int	index(int row, int column) Returns the position of the given coordinate within the (virtual or non-virtual) internal 1-dimensional array.
DoubleMatrix2D	like(int rows, int columns) Construct and returns a new empty matrix of the same dynamic type as the receiver, having the specified number of rows and columns.
DoubleMatrix1D	like1D(int size) Construct and returns a new 1-d matrix of the corresponding dynamic type, entirelly independent of the receiver.
void	setQuick(int row, int column, double value) Sets the matrix cell at coordinate [row,column] to the specified value.
void	trimToSize() Releases any superfluous memory created by explicitly putting zero values into cells formerly having non-zero values; An application can use this operation to minimize the storage of the receiver.
DoubleMatrix1D	vectorize() Returns a vector obtained by stacking the columns of the matrix on top of one another.
DoubleMatrix1D	zMult(DoubleMatrix1D y, DoubleMatrix1D z, double alpha, double beta, boolean transposeA) Linear algebraic matrix-vector multiplication; z = alpha * A * y + beta*z.
DoubleMatrix2D	zMult(DoubleMatrix2D B, DoubleMatrix2D C, double alpha, double beta, boolean transposeA, boolean transposeB) Linear algebraic matrix-matrix multiplication; C = alpha * A x B + beta*C.

Methods inherited from class cern.colt.matrix.tdouble.DoubleMatrix2D

aggregate, aggregate, aggregate, aggregate, assign, assign, assign, assign, assign, assign, copy, equals, equals, get, getMaxLocation, getMinLocation, getNegativeValues, getNonZeros, getPositiveValues, like, normalize, set, setNcolumns, setNrows, toArray, toString, viewColumn, viewColumnFlip, viewDice, viewPart, viewRow, viewRowFlip, viewSelection, viewSelection, viewSelection, viewSorted, viewStrides, zAssign8Neighbors, zMult, zMult, zSum

Methods inherited from class cern.colt.matrix.AbstractMatrix2D

checkShape, checkShape, columns, columnStride, rows, rowStride, size, toStringShort

Methods inherited from class cern.colt.matrix.AbstractMatrix

isView

Methods inherited from class cern.colt.PersistentObject

clone

Methods inherited from class java.lang.Object

getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

SparseDoubleMatrix2D

public SparseDoubleMatrix2D(double[][] values)

Constructs a matrix with a copy of the given values. values is required to have the form values[row][column] and have exactly the same number of columns in every row.

The values are copied. So subsequent changes in values are not reflected in the matrix, and vice-versa.

Parameters:

values - The values to be filled into the new matrix.

Throws:

IllegalArgumentException - if for any 1 <= row < values.length: values[row].length != values[row-1].length.

SparseDoubleMatrix2D

public SparseDoubleMatrix2D(int rows,
                            int columns)

Constructs a matrix with a given number of rows and columns and default memory usage. All entries are initially 0.

Parameters:

rows - the number of rows the matrix shall have.

columns - the number of columns the matrix shall have.

Throws:

IllegalArgumentException - if rows<0 || columns<0 || (double)columns*rows > Integer.MAX_VALUE.

SparseDoubleMatrix2D

public SparseDoubleMatrix2D(int rows,
                            int columns,
                            int initialCapacity,
                            double minLoadFactor,
                            double maxLoadFactor)

Constructs a matrix with a given number of rows and columns using memory as specified. All entries are initially 0. For details related to memory usage see OpenIntDoubleHashMap.

Parameters:

rows - the number of rows the matrix shall have.

columns - the number of columns the matrix shall have.

initialCapacity - the initial capacity of the hash map. If not known, set initialCapacity=0 or small.

minLoadFactor - the minimum load factor of the hash map.

maxLoadFactor - the maximum load factor of the hash map.

Throws:

IllegalArgumentException - if initialCapacity < 0 || (minLoadFactor < 0.0 || minLoadFactor >= 1.0) || (maxLoadFactor <= 0.0 || maxLoadFactor >= 1.0) || (minLoadFactor >= maxLoadFactor).

IllegalArgumentException - if rows<0 || columns<0 || (double)columns*rows > Integer.MAX_VALUE.

Method Detail

assign

public DoubleMatrix2D assign(DoubleFunction function)

Assigns the result of a function to each cell; x[row,col] = function(x[row,col]).

Example:

         matrix = 2 x 2 matrix
         0.5 1.5      
         2.5 3.5
 
         // change each cell to its sine
         matrix.assign(cern.jet.math.Functions.sin);
         -->
         2 x 2 matrix
         0.479426  0.997495 
         0.598472 -0.350783
        
 

For further examples, see the package doc.

Overrides:

assign in class DoubleMatrix2D

Parameters:

function - a function object taking as argument the current cell's value.

Returns:

this (for convenience only).

See Also:

DoubleFunctions

assign

public DoubleMatrix2D assign(double value)

Sets all cells to the state specified by value.

Overrides:

assign in class DoubleMatrix2D

Parameters:

value - the value to be filled into the cells.

Returns:

this (for convenience only).

assign

public DoubleMatrix2D assign(DoubleMatrix2D source)

Replaces all cell values of the receiver with the values of another matrix. Both matrices must have the same number of rows and columns. If both matrices share the same cells (as is the case if they are views derived from the same matrix) and intersect in an ambiguous way, then replaces as if using an intermediate auxiliary deep copy of other.

Overrides:

assign in class DoubleMatrix2D

Parameters:

source - the source matrix to copy from (may be identical to the receiver).

Returns:

this (for convenience only).

Throws:

IllegalArgumentException - if columns() != source.columns() || rows() != source.rows()

assign

public DoubleMatrix2D assign(DoubleMatrix2D y,
                             DoubleDoubleFunction function)

Description copied from class: DoubleMatrix2D

Assigns the result of a function to each cell; x[row,col] = function(x[row,col],y[row,col]).

Example:

         // assign x[row,col] = x[row,col]<sup>y[row,col]</sup>
         m1 = 2 x 2 matrix 
         0 1 
         2 3
 
         m2 = 2 x 2 matrix 
         0 2 
         4 6
 
         m1.assign(m2, cern.jet.math.Functions.pow);
         -->
         m1 == 2 x 2 matrix
         1   1 
         16 729
 
 

For further examples, see the package doc.

Overrides:

assign in class DoubleMatrix2D

Parameters:

y - the secondary matrix to operate on.

function - a function object taking as first argument the current cell's value of this, and as second argument the current cell's value of y,

Returns:

this (for convenience only).

See Also:

DoubleFunctions

cardinality

public int cardinality()

Returns the number of cells having non-zero values.

Overrides:

cardinality in class DoubleMatrix2D

Returns:

cardinality

dct2

public void dct2(boolean scale)

Description copied from class: DoubleMatrix2D

Computes the 2D discrete cosine transform (DCT-II) of this matrix.

Specified by:

dct2 in class DoubleMatrix2D

Parameters:

scale - if true then scaling is performed

dctColumns

public void dctColumns(boolean scale)

Description copied from class: DoubleMatrix2D

Computes the discrete cosine transform (DCT-II) of each column of this matrix.

Specified by:

dctColumns in class DoubleMatrix2D

Parameters:

scale - if true then scaling is performed

dctRows

public void dctRows(boolean scale)

Description copied from class: DoubleMatrix2D

Computes the discrete cosine transform (DCT-II) of each row of this matrix.

Specified by:

dctRows in class DoubleMatrix2D

Parameters:

scale - if true then scaling is performed

dht2

public void dht2()

Description copied from class: DoubleMatrix2D

Computes the 2D discrete Hartley transform (DHT) of this matrix.

Specified by:

dht2 in class DoubleMatrix2D

dhtColumns

public void dhtColumns()

Description copied from class: DoubleMatrix2D

Computes the discrete Hartley transform (DHT) of each column of this matrix.

Specified by:

dhtColumns in class DoubleMatrix2D

dhtRows

public void dhtRows()

Description copied from class: DoubleMatrix2D

Computes the discrete Hartley transform (DHT) of each row of this matrix.

Specified by:

dhtRows in class DoubleMatrix2D

dst2

public void dst2(boolean scale)

Description copied from class: DoubleMatrix2D

Computes the 2D discrete sine transform (DST-II) of this matrix.

Specified by:

dst2 in class DoubleMatrix2D

Parameters:

scale - if true then scaling is performed

dstColumns

public void dstColumns(boolean scale)

Description copied from class: DoubleMatrix2D

Computes the discrete sine transform (DST-II) of each column of this matrix.

Specified by:

dstColumns in class DoubleMatrix2D

Parameters:

scale - if true then scaling is performed

dstRows

public void dstRows(boolean scale)

Description copied from class: DoubleMatrix2D

Computes the discrete sine transform (DST-II) of each row of this matrix.

Specified by:

dstRows in class DoubleMatrix2D

Parameters:

scale - if true then scaling is performed

elements

public AbstractIntDoubleMap elements()

Returns the elements of this matrix.

Specified by:

elements in class DoubleMatrix2D

Returns:

the elements

ensureCapacity

public void ensureCapacity(int minCapacity)

Ensures that the receiver can hold at least the specified number of non-zero cells without needing to allocate new internal memory. If necessary, allocates new internal memory and increases the capacity of the receiver.

This method never need be called; it is for performance tuning only. Calling this method before tt>set()ing a large number of non-zero values boosts performance, because the receiver will grow only once instead of potentially many times and hash collisions get less probable.

Overrides:

ensureCapacity in class AbstractMatrix

Parameters:

minCapacity - the desired minimum number of non-zero cells.

fft2

public void fft2()

Description copied from class: DoubleMatrix2D

Computes the 2D discrete Fourier transform (DFT) of this matrix. The physical layout of the output data is as follows:

 this[k1][2*k2] = Re[k1][k2] = Re[rows-k1][columns-k2], 
 this[k1][2*k2+1] = Im[k1][k2] = -Im[rows-k1][columns-k2], 
       0<k1<rows, 0<k2<columns/2, 
 this[0][2*k2] = Re[0][k2] = Re[0][columns-k2], 
 this[0][2*k2+1] = Im[0][k2] = -Im[0][columns-k2], 
       0<k2<columns/2, 
 this[k1][0] = Re[k1][0] = Re[rows-k1][0], 
 this[k1][1] = Im[k1][0] = -Im[rows-k1][0], 
 this[rows-k1][1] = Re[k1][columns/2] = Re[rows-k1][columns/2], 
 this[rows-k1][0] = -Im[k1][columns/2] = Im[rows-k1][columns/2], 
       0<k1<rows/2, 
 this[0][0] = Re[0][0], 
 this[0][1] = Re[0][columns/2], 
 this[rows/2][0] = Re[rows/2][0], 
 this[rows/2][1] = Re[rows/2][columns/2]
 

This method computes only half of the elements of the real transform. The other half satisfies the symmetry condition. If you want the full real forward transform, use getFft2. To get back the original data, use ifft2.

Specified by:

fft2 in class DoubleMatrix2D

forEachNonZero

public DoubleMatrix2D forEachNonZero(IntIntDoubleFunction function)

Description copied from class: DoubleMatrix2D

Assigns the result of a function to each non-zero cell; x[row,col] = function(x[row,col]). Use this method for fast special-purpose iteration. If you want to modify another matrix instead of this (i.e. work in read-only mode), simply return the input value unchanged. Parameters to function are as follows: first==row, second==column, third==nonZeroValue.

Overrides:

forEachNonZero in class DoubleMatrix2D

Parameters:

function - a function object taking as argument the current non-zero cell's row, column and value.

Returns:

this (for convenience only).

getFft2

public DComplexMatrix2D getFft2()

Description copied from class: DoubleMatrix2D

Returns new complex matrix which is the 2D discrete Fourier transform (DFT) of this matrix.

Specified by:

getFft2 in class DoubleMatrix2D

Returns:

the 2D discrete Fourier transform (DFT) of this matrix.

getFftColumns

public DComplexMatrix2D getFftColumns()

Description copied from class: DoubleMatrix2D

Returns new complex matrix which is the discrete Fourier transform (DFT) of each column of this matrix.

Specified by:

getFftColumns in class DoubleMatrix2D

Returns:

the discrete Fourier transform (DFT) of each column of this matrix.

getFftRows

public DComplexMatrix2D getFftRows()

Description copied from class: DoubleMatrix2D

Returns new complex matrix which is the discrete Fourier transform (DFT) of each row of this matrix.

Specified by:

getFftRows in class DoubleMatrix2D

Returns:

the discrete Fourier transform (DFT) of each row of this matrix.

getIfft2

public DComplexMatrix2D getIfft2(boolean scale)

Description copied from class: DoubleMatrix2D

Returns new complex matrix which is the 2D inverse of the discrete Fourier transform (IDFT) of this matrix.

Specified by:

getIfft2 in class DoubleMatrix2D

Returns:

the 2D inverse of the discrete Fourier transform (IDFT) of this matrix.

getIfftColumns

public DComplexMatrix2D getIfftColumns(boolean scale)

Description copied from class: DoubleMatrix2D

Returns new complex matrix which is the inverse of the discrete Fourier transform (IDFT) of each column of this matrix.

Specified by:

getIfftColumns in class DoubleMatrix2D

Returns:

the inverse of the discrete Fourier transform (IDFT) of each column of this matrix.

getIfftRows

public DComplexMatrix2D getIfftRows(boolean scale)

Description copied from class: DoubleMatrix2D

Returns new complex matrix which is the inverse of the discrete Fourier transform (IDFT) of each row of this matrix.

Specified by:

getIfftRows in class DoubleMatrix2D

Returns:

the inverse of the discrete Fourier transform (IDFT) of each row of this matrix.

getQuick

public double getQuick(int row,
                       int column)

Returns the matrix cell value at coordinate [row,column].

Provided with invalid parameters this method may return invalid objects without throwing any exception. You should only use this method when you are absolutely sure that the coordinate is within bounds. Precondition (unchecked): 0 <= column < columns() && 0 <= row < rows().

Specified by:

getQuick in class DoubleMatrix2D

Parameters:

row - the index of the row-coordinate.

column - the index of the column-coordinate.

Returns:

the value at the specified coordinate.

idct2

public void idct2(boolean scale)

Description copied from class: DoubleMatrix2D

Computes the 2D inverse of the discrete cosine transform (DCT-III) of this matrix.

Specified by:

idct2 in class DoubleMatrix2D

Parameters:

scale - if true then scaling is performed

idctColumns

public void idctColumns(boolean scale)

Description copied from class: DoubleMatrix2D

Computes the inverse of the discrete cosine transform (DCT-III) of each column of this matrix.

Specified by:

idctColumns in class DoubleMatrix2D

Parameters:

scale - if true then scaling is performed

idctRows

public void idctRows(boolean scale)

Description copied from class: DoubleMatrix2D

Computes the inverse of the discrete cosine transform (DCT-III) of each row of this matrix.

Specified by:

idctRows in class DoubleMatrix2D

Parameters:

scale - if true then scaling is performed

idht2

public void idht2(boolean scale)

Description copied from class: DoubleMatrix2D

Computes the 2D inverse of the discrete Hartley transform (IDHT) of this matrix.

Specified by:

idht2 in class DoubleMatrix2D

Parameters:

scale - if true then scaling is performed

idhtColumns

public void idhtColumns(boolean scale)

Description copied from class: DoubleMatrix2D

Computes the inverse of the discrete Hartley transform (IDHT) of each column of this matrix.

Specified by:

idhtColumns in class DoubleMatrix2D

Parameters:

scale - if true then scaling is performed

idhtRows

public void idhtRows(boolean scale)

Description copied from class: DoubleMatrix2D

Computes the inverse of the discrete Hartley transform (IDHT) of each row of this matrix.

Specified by:

idhtRows in class DoubleMatrix2D

Parameters:

scale - if true then scaling is performed

idst2

public void idst2(boolean scale)

Description copied from class: DoubleMatrix2D

Computes the 2D inverse of the discrete sine transform (DST-III) of this matrix.

Specified by:

idst2 in class DoubleMatrix2D

Parameters:

scale - if true then scaling is performed

idstColumns

public void idstColumns(boolean scale)

Description copied from class: DoubleMatrix2D

Computes the inverse of the discrete sine transform (DST-III) of each column of this matrix.

Specified by:

idstColumns in class DoubleMatrix2D

Parameters:

scale - if true then scaling is performed

idstRows

public void idstRows(boolean scale)

Description copied from class: DoubleMatrix2D

Computes the inverse of the discrete sine transform (DST-III) of each row of this matrix.

Specified by:

idstRows in class DoubleMatrix2D

Parameters:

scale - if true then scaling is performed

ifft2

public void ifft2(boolean scale)

Description copied from class: DoubleMatrix2D

Computes the 2D inverse of the discrete Fourier transform (IDFT) of this matrix. The physical layout of the input data has to be as follows:

 this[k1][2*k2] = Re[k1][k2] = Re[rows-k1][columns-k2], 
 this[k1][2*k2+1] = Im[k1][k2] = -Im[rows-k1][columns-k2], 
       0<k1<rows, 0<k2<columns/2, 
 this[0][2*k2] = Re[0][k2] = Re[0][columns-k2], 
 this[0][2*k2+1] = Im[0][k2] = -Im[0][columns-k2], 
       0<k2<columns/2, 
 this[k1][0] = Re[k1][0] = Re[rows-k1][0], 
 this[k1][1] = Im[k1][0] = -Im[rows-k1][0], 
 this[rows-k1][1] = Re[k1][columns/2] = Re[rows-k1][columns/2], 
 this[rows-k1][0] = -Im[k1][columns/2] = Im[rows-k1][columns/2], 
       0<k1<rows/2, 
 this[0][0] = Re[0][0], 
 this[0][1] = Re[0][columns/2], 
 this[rows/2][0] = Re[rows/2][0], 
 this[rows/2][1] = Re[rows/2][columns/2]
 

This method computes only half of the elements of the real transform. The other half satisfies the symmetry condition. If you want the full real inverse transform, use getIfft2.

Specified by:

ifft2 in class DoubleMatrix2D

Parameters:

scale - if true then scaling is performed

index

public int index(int row,
                 int column)

Returns the position of the given coordinate within the (virtual or non-virtual) internal 1-dimensional array.

Overrides:

index in class AbstractMatrix2D

Parameters:

row - the index of the row-coordinate.

column - the index of the column-coordinate.

like

public DoubleMatrix2D like(int rows,
                           int columns)

Construct and returns a new empty matrix of the same dynamic type as the receiver, having the specified number of rows and columns. For example, if the receiver is an instance of type DenseDoubleMatrix2D the new matrix must also be of type DenseDoubleMatrix2D, if the receiver is an instance of type SparseDoubleMatrix2D the new matrix must also be of type SparseDoubleMatrix2D, etc. In general, the new matrix should have internal parametrization as similar as possible.

Specified by:

like in class DoubleMatrix2D

Parameters:

rows - the number of rows the matrix shall have.

columns - the number of columns the matrix shall have.

Returns:

a new empty matrix of the same dynamic type.

like1D

public DoubleMatrix1D like1D(int size)

Construct and returns a new 1-d matrix of the corresponding dynamic type, entirelly independent of the receiver. For example, if the receiver is an instance of type DenseDoubleMatrix2D the new matrix must be of type DenseDoubleMatrix1D, if the receiver is an instance of type SparseDoubleMatrix2D the new matrix must be of type SparseDoubleMatrix1D, etc.

Specified by:

like1D in class DoubleMatrix2D

Parameters:

size - the number of cells the matrix shall have.

Returns:

a new matrix of the corresponding dynamic type.

setQuick

public void setQuick(int row,
                     int column,
                     double value)

Sets the matrix cell at coordinate [row,column] to the specified value.

Provided with invalid parameters this method may access illegal indexes without throwing any exception. You should only use this method when you are absolutely sure that the coordinate is within bounds. Precondition (unchecked): 0 <= column < columns() && 0 <= row < rows().

Specified by:

setQuick in class DoubleMatrix2D

Parameters:

row - the index of the row-coordinate.

column - the index of the column-coordinate.

value - the value to be filled into the specified cell.

trimToSize

public void trimToSize()

Releases any superfluous memory created by explicitly putting zero values into cells formerly having non-zero values; An application can use this operation to minimize the storage of the receiver.

Background:

Cells that

• are never set to non-zero values do not use any memory.
• switch from zero to non-zero state do use memory.
• switch back from non-zero to zero state also do use memory. However, their memory can be reclaimed by calling trimToSize().

A sequence like set(r,c,5); set(r,c,0); sets a cell to non-zero state and later back to zero state. Such as sequence generates obsolete memory that is automatically reclaimed from time to time or can manually be reclaimed by calling trimToSize(). Putting zeros into cells already containing zeros does not generate obsolete memory since no memory was allocated to them in the first place.

Overrides:

trimToSize in class AbstractMatrix

vectorize

public DoubleMatrix1D vectorize()

Returns a vector obtained by stacking the columns of the matrix on top of one another.

Specified by:

vectorize in class DoubleMatrix2D

Returns:

a vector obtained by stacking the columns of the matrix on top of one another

zMult

public DoubleMatrix1D zMult(DoubleMatrix1D y,
                            DoubleMatrix1D z,
                            double alpha,
                            double beta,
                            boolean transposeA)

Description copied from class: DoubleMatrix2D

Linear algebraic matrix-vector multiplication; z = alpha * A * y + beta*z. z[i] = alpha*Sum(A[i,j] * y[j]) + beta*z[i], i=0..A.rows()-1, j=0..y.size()-1 . Where A == this.
Note: Matrix shape conformance is checked after potential transpositions.

Overrides:

zMult in class DoubleMatrix2D

Parameters:

y - the source vector.

z - the vector where results are to be stored. Set this parameter to null to indicate that a new result vector shall be constructed.

Returns:

z (for convenience only).

zMult

public DoubleMatrix2D zMult(DoubleMatrix2D B,
                            DoubleMatrix2D C,
                            double alpha,
                            double beta,
                            boolean transposeA,
                            boolean transposeB)

Description copied from class: DoubleMatrix2D

Linear algebraic matrix-matrix multiplication; C = alpha * A x B + beta*C. C[i,j] = alpha*Sum(A[i,k] * B[k,j]) + beta*C[i,j], k=0..n-1.
Matrix shapes: A(m x n), B(n x p), C(m x p).
Note: Matrix shape conformance is checked after potential transpositions.

Overrides:

zMult in class DoubleMatrix2D

Parameters:

B - the second source matrix.

C - the matrix where results are to be stored. Set this parameter to null to indicate that a new result matrix shall be constructed.

Returns:

C (for convenience only).