no.uib.cipr.matrix
Interface Vector

All Superinterfaces:
java.lang.Iterable<VectorEntry>, java.io.Serializable
All Known Subinterfaces:
ISparseVector
All Known Implementing Classes:
AbstractVector, DenseVector, DistVector, SparseVector

public interface Vector
extends java.lang.Iterable<VectorEntry>, java.io.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
static class Vector.Norm
          Supported vector-norms.
 
Method Summary
 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