cern.colt.matrix.impl
Class SparseDoubleMatrix1D

java.lang.Object
  cern.colt.PersistentObject
      cern.colt.matrix.impl.AbstractMatrix
          cern.colt.matrix.impl.AbstractMatrix1D
              cern.colt.matrix.DoubleMatrix1D
                  cern.colt.matrix.impl.SparseDoubleMatrix1D

All Implemented Interfaces:

Cloneable, Serializable

public class SparseDoubleMatrix1D

extends DoubleMatrix1D

Sparse hashed 1-d matrix (aka vector) 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 1000000 matrix with minLoadFactor=0.25 and maxLoadFactor=0.5 and 1000000 non-zero cells consumes between 25 MB and 50 MB. The same 1000000 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 DenseDoubleMatrix1D. However, constant factors are considerably larger.

Version:

1.0, 09/24/99

See Also:

Serialized Form

SparseDoubleMatrix1D

public SparseDoubleMatrix1D(double[] values)

Constructs a matrix with a copy of the given values. 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.

SparseDoubleMatrix1D

public SparseDoubleMatrix1D(int size)

Constructs a matrix with a given number of cells. All entries are initially 0.

Parameters:

size - the number of cells the matrix shall have.

Throws:

IllegalArgumentException - if size<0.

SparseDoubleMatrix1D

public SparseDoubleMatrix1D(int size,
                            int initialCapacity,
                            double minLoadFactor,
                            double maxLoadFactor)

Constructs a matrix with a given number of parameters. All entries are initially 0. For details related to memory usage see OpenIntDoubleHashMap.

Parameters:

size - the number of cells 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 size<0.

assign

public DoubleMatrix1D assign(double value)

Sets all cells to the state specified by value.

Overrides:

assign in class DoubleMatrix1D

Parameters:

value - the value to be filled into the cells.

Returns:

this (for convenience only).

cardinality

public int cardinality()

Returns the number of cells having non-zero values.

Overrides:

cardinality in class DoubleMatrix1D

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 (non-null) cells.

getQuick

public double getQuick(int index)

Returns the matrix cell value at coordinate index.

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): index<0 || index>=size().

Specified by:

getQuick in class DoubleMatrix1D

Parameters:

index - the index of the cell.

Returns:

the value of the specified cell.

like

public DoubleMatrix1D like(int size)

Construct and returns a new empty matrix of the same dynamic type as the receiver, having the specified size. For example, if the receiver is an instance of type DenseDoubleMatrix1D the new matrix must also be of type DenseDoubleMatrix1D, if the receiver is an instance of type SparseDoubleMatrix1D the new matrix must also be of type SparseDoubleMatrix1D, etc. In general, the new matrix should have internal parametrization as similar as possible.

Specified by:

like in class DoubleMatrix1D

Parameters:

size - the number of cell the matrix shall have.

Returns:

a new empty matrix of the same dynamic type.

like2D

public DoubleMatrix2D like2D(int rows,
                             int columns)

Construct and returns a new 2-d matrix of the corresponding dynamic type, entirelly independent of the receiver. For example, if the receiver is an instance of type DenseDoubleMatrix1D the new matrix must be of type DenseDoubleMatrix2D, if the receiver is an instance of type SparseDoubleMatrix1D the new matrix must be of type SparseDoubleMatrix2D, etc.

Specified by:

like2D in class DoubleMatrix1D

Parameters:

rows - the number of rows the matrix shall have.

columns - the number of columns the matrix shall have.

Returns:

a new matrix of the corresponding dynamic type.

setQuick

public void setQuick(int index,
                     double value)

Sets the matrix cell at coordinate index 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): index<0 || index>=size().

Specified by:

setQuick in class DoubleMatrix1D

Parameters:

index - the index of the cell.

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(i,5); set(i,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