edu.ucla.sspace.matrix

Class SparseSymmetricMatrix

java.lang.Object

edu.ucla.sspace.matrix.AbstractMatrix

edu.ucla.sspace.matrix.SparseSymmetricMatrix

All Implemented Interfaces:

Matrix, SparseMatrix, Serializable

public class SparseSymmetricMatrix
extends AbstractMatrix
implements SparseMatrix, Serializable

A decorator around a SparseMatrix that keeps only the upper triangular values while providing a symmetric view of the data. This class only records changes values where row > col. For all other values, the row and column values are swapped and then the backing matrix is updated. Note, that if the provided backing matrix has existing values for indices row < col, these values will be ignored and never returned from any method. Note the original perfomance characteristics of the backing matrix are retained by this class.

The primary benfit of this class is for storing large symmetric sparse matrices in half of the memory.

Author:

David Jurgens

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface edu.ucla.sspace.matrix.Matrix

Matrix.Type

Constructor Summary

Constructors

Constructor and Description
SparseSymmetricMatrix(SparseMatrix backing) Constructs a sparse matrix with the specified dimensions.

Method Summary

Methods

Modifier and Type	Method and Description
int	columns() Returns the number of columns in this Matrix.
double	get(int row, int column) Returns the value of the Matrix at the provided row and column.
SparseDoubleVector	getColumnVector(int column) Returns the column as a vector.
SparseDoubleVector	getRowVector(int row) Returns a DoubleVector for an entire row.
int	rows() Returns the number of rows in this Matrix.
void	set(int row, int column, double val) Throws an UnsupportedOperationException if called (matrix is unmodifiable).

Methods inherited from class edu.ucla.sspace.matrix.AbstractMatrix

equals, getColumn, getRow, hashCode, setColumn, setColumn, setRow, setRow, toDenseArray

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface edu.ucla.sspace.matrix.Matrix

getColumn, getRow, setColumn, setColumn, setRow, setRow, toDenseArray

Constructor Detail

SparseSymmetricMatrix

public SparseSymmetricMatrix(SparseMatrix backing)

Constructs a sparse matrix with the specified dimensions.

Method Detail

columns

public int columns()

Returns the number of columns in this Matrix.

Specified by:

columns in interface Matrix

Specified by:

columns in class AbstractMatrix

Returns:

The number of columns in this Matrix.

get

public double get(int row,
         int column)

Returns the value of the Matrix at the provided row and column.

Specified by:

get in interface Matrix

Overrides:

get in class AbstractMatrix

Parameters:

row - The row values of the cell to return.

column - The column value of the cell to return.

Returns:

The value at the cell specified by row and col.

getColumnVector

public SparseDoubleVector getColumnVector(int column)

Returns the column as a vector. Whether updates to the vector are written through to the backing matrix is left open to the specific implementation. Implementations that maintain their data in a sparse format are encouraged to return a SparseVector instance.

Specified by:

getColumnVector in interface Matrix

Specified by:

getColumnVector in interface SparseMatrix

Overrides:

getColumnVector in class AbstractMatrix

Parameters:

column - The column to return a DoubleVector for.

Returns:

A DoubleVector representing the column at column.

getRowVector

public SparseDoubleVector getRowVector(int row)

Returns a DoubleVector for an entire row. Implementations should return an approriately typed DoubleVector. Whether updates to the vector are written through to the backing matrix is left open to the specific implementation. Implementations that maintain their data in a sparse format are encouraged to return a SparseVector instance.

Specified by:

getRowVector in interface Matrix

Specified by:

getRowVector in interface SparseMatrix

Specified by:

getRowVector in class AbstractMatrix

Parameters:

row - the index of the row to return.

Returns:

A DoubleVector representing the row at row.

rows

public int rows()

Returns the number of rows in this Matrix.

Specified by:

rows in interface Matrix

Specified by:

rows in class AbstractMatrix

Returns:

The number of columns in this Matrix.

set

public void set(int row,
       int column,
       double val)

Throws an UnsupportedOperationException if called (matrix is unmodifiable).

Specified by:

set in interface Matrix

Overrides:

set in class AbstractMatrix

Parameters:

row - The row of the cell to update.

column - The column of the cell to update.

val - The new value of the specified cell.