org.graphstream.algorithm

Class AStar.DefaultCosts

java.lang.Object

org.graphstream.algorithm.AStar.DefaultCosts

All Implemented Interfaces:

AStar.Costs

Enclosing class:

AStar

public static class AStar.DefaultCosts
extends java.lang.Object
implements AStar.Costs

An implementation of the Costs interface that provides a default heuristic. It computes the G part using "weights" on edges. These weights must be stored in an attribute on edges. By default this attribute must be named "weight", but this can be changed. The weight attribute must be a Number an must be translatable to a double value. This implementation always return 0 for the H value. This makes the A* algorithm an equivalent of the Dijkstra algorithm.

Constructor Summary

Constructors

Constructor and Description
DefaultCosts() New default costs for the A* algorithm.
DefaultCosts(java.lang.String weightAttributeName) New default costs for the A* algorithm.

Method Summary

Modifier and Type	Method and Description
double	cost(org.graphstream.graph.Node parent, org.graphstream.graph.Edge edge, org.graphstream.graph.Node next) The cost of moving from parent to next.
double	heuristic(org.graphstream.graph.Node node, org.graphstream.graph.Node target) The heuristic.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DefaultCosts

public DefaultCosts()

New default costs for the A* algorithm. The cost of each edge is obtained from a numerical attribute stored under the name "weight". This attribute must be a descendant of Number (Double, Float, Integer, etc.).

DefaultCosts

public DefaultCosts(java.lang.String weightAttributeName)

New default costs for the A* algorithm. The cost of each edge is obtained from the attribute stored on each edge under the "weightAttributeName". This attribute must be a descendant of Number (Double, Float, Integer, etc.).

Parameters:

weightAttributeName - The name of cost attributes on edges.

Method Detail

heuristic

public double heuristic(org.graphstream.graph.Node node,
                        org.graphstream.graph.Node target)

The heuristic. This one always returns zero, therefore transforming this A* into the Dijkstra algorithm.

Specified by:

heuristic in interface AStar.Costs

Parameters:

node - A node.

target - The target node.

Returns:

The estimation.

cost

public double cost(org.graphstream.graph.Node parent,
                   org.graphstream.graph.Edge edge,
                   org.graphstream.graph.Node next)

The cost of moving from parent to next. If there is no cost attribute, the edge is considered to cost value "1".

Specified by:

cost in interface AStar.Costs

Parameters:

parent - The node we come from.

edge - The edge between parent and next.

next - The node we go to.

Returns:

The movement cost.