no.uib.cipr.matrix

Interface Vector

All Superinterfaces:

Iterable<VectorEntry>, Serializable

All Known Subinterfaces:

ISparseVector

All Known Implementing Classes:

AbstractVector, DenseVector, DenseVectorSub, SparseVector

public interface Vector
extends Iterable<VectorEntry>, Serializable

Basic vector interface. It holds doubles in an array, and is used alongside Matrix in numerical computations. Implementing classes decides on the actual storage.

Basic operations

Use size to get the vector size. get(int) gets an element, and there are corresponding set(int,double) and add(int,double) methods as well. Note that vector indices are zero-based (typical for Java and C). This means that they range from 0 to size-1. It is legal to have size equal zero.

Other basic operations are zero which zeros all the entries of the vector, which can be cheaper than either zeroing the vector manually, or creating a new vector, and the operation copy which creates a deep copy of the vector. This copy has separate storage, but starts with the same contents as the current vector.

Iterators

The vector interface extends Iterable, and the iterator returns a VectorEntry which contains current index and entry value. Note that the iterator may skip non-zero entries. Using an iterator, many simple and efficient algorithms can be created. The iterator also permits changing values in the vector, however only non-zero entries can be changed.

Basic linear algebra

A selection of basic linear algebra operations are available. To ensure high efficiency, little or no internal memory allocation is done, and the user is required to supply the output arguments.

The operations available include:

Additions

Vectors can be added to each other, even if their underlying vector structures are incompatible

Scaling

Scalar multiplication (scaling) of a whole vector

Norms

Both innerproducts and norms can be computed. Several common norms are supported

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	Vector.Norm Supported vector-norms.

Method Summary

Methods

Modifier and Type	Method and Description
Vector	add(double alpha, Vector y) x = alpha*y + x
void	add(int index, double value) x(index) += value
Vector	add(Vector y) x = y + x
Vector	copy() Creates a deep copy of the vector
double	dot(Vector y) xT*y
double	get(int index) Returns x(index)
double	norm(Vector.Norm type) Computes the given norm of the vector
Vector	scale(double alpha) x=alpha*x
Vector	set(double alpha, Vector y) x=alpha*y
void	set(int index, double value) x(index) = value
Vector	set(Vector y) x=y
int	size() Size of the vector
Vector	zero() Zeros all the entries in the vector, while preserving any underlying structure

Methods inherited from interface java.lang.Iterable

iterator

Method Detail

size

int size()

Size of the vector

set

void set(int index,
       double value)

x(index) = value

add

void add(int index,
       double value)

x(index) += value

get

double get(int index)

Returns x(index)

copy

Vector copy()

Creates a deep copy of the vector

zero

Vector zero()

Zeros all the entries in the vector, while preserving any underlying structure

scale

Vector scale(double alpha)

x=alpha*x

Returns:

x

set

Vector set(Vector y)

x=y

Returns:

x

set

Vector set(double alpha,
         Vector y)

x=alpha*y

Returns:

x

add

Vector add(Vector y)

x = y + x

Returns:

x

add

Vector add(double alpha,
         Vector y)

x = alpha*y + x

Returns:

x

dot

double dot(Vector y)

xT*y

norm

double norm(Vector.Norm type)

Computes the given norm of the vector

Parameters:

type - The type of norm to compute