org.graphstream.algorithm

Class Prim

java.lang.Object

org.graphstream.algorithm.AbstractSpanningTree

org.graphstream.algorithm.Kruskal

org.graphstream.algorithm.Prim

All Implemented Interfaces:

Algorithm, SpanningTree

public class Prim
extends Kruskal

Compute a spanning tree using the Prim algorithm.

Prim's algorithm is an algorithm which allows to find a minimal spanning tree in a weighted connected graph. More informations on Wikipedia.

Example

The following example generates a graph with the Dorogovtsev-Mendes generator and then compute a spanning-tree using the Prim algorithm. The generator creates random weights for edges that will be used by the Prim algorithm. If no weight is present, algorithm considers that all weights are set to 1. When an edge is in the spanning tree, the algorithm will set its "ui.class" attribute to "intree", else the attribute is set to "notintree". According to the css stylesheet that is defined, spanning will be displayed with thick black lines while edges not in the spanning tree will be displayed with thin gray lines.

 import org.graphstream.graph.Graph;
 import org.graphstream.graph.implementations.DefaultGraph;
 
 import org.graphstream.algorithm.Prim;
 import org.graphstream.algorithm.generator.DorogovtsevMendesGenerator;
 
 public class PrimTest {
 
        public static void main(String... args) {
                DorogovtsevMendesGenerator gen = new DorogovtsevMendesGenerator();
                Graph graph = new DefaultGraph("Prim Test");
 
                String css = "edge .notintree {size:1px;fill-color:gray;} "
                                + "edge .intree {size:3px;fill-color:black;}";
 
                graph.addAttribute("ui.stylesheet", css);
                graph.display();
 
                gen.addEdgeAttribute("weight");
                gen.setEdgeAttributesRange(1, 100);
                gen.addSink(graph);
                gen.begin();
                for (int i = 0; i < 100 && gen.nextEvents(); i++)
                        ;
                gen.end();
 
                Prim prim = new Prim("ui.class", "intree", "notintree");
 
                prim.init(graph);
                prim.compute();
        }
 }
 

See Also:

AbstractSpanningTree

Computational Complexity:

0(m + n log n), where m is the number of edges and n is the number of nodes in the graph

Scientific Reference:

R. C. Prim: Shortest connection networks and some generalizations. In: Bell System Technical Journal, 36 (1957), pp. 1389–1401

Field Summary

Fields inherited from class org.graphstream.algorithm.Kruskal

DEFAULT_WEIGHT_ATTRIBUTE

Constructor Summary

Constructors

Constructor and Description
Prim() Create a new Prim's algorithm.
Prim(java.lang.String flagAttribute, java.lang.Object flagOn, java.lang.Object flagOff) Create a new Prim's algorithm.
Prim(java.lang.String weightAttribute, java.lang.String flagAttribute) Create a new Prim's algorithm.
Prim(java.lang.String weightAttribute, java.lang.String flagAttribute, java.lang.Object flagOn, java.lang.Object flagOff) Create a new Prim's algorithm.

Method Summary

Modifier and Type	Method and Description
java.lang.String	defaultResult()

Methods inherited from class org.graphstream.algorithm.Kruskal

clear, getTreeEdgesStream, getTreeWeight, getWeightAttribute, setWeightAttribute

Methods inherited from class org.graphstream.algorithm.AbstractSpanningTree

compute, getFlagAttribute, getFlagOff, getFlagOn, getTreeEdges, init, setFlagAttribute, setFlagOff, setFlagOn

Methods inherited from class java.lang.Object

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

Constructor Detail

Prim

public Prim()

Create a new Prim's algorithm. Uses the default weight attribute and does not tag the edges.

Prim

public Prim(java.lang.String weightAttribute,
            java.lang.String flagAttribute)

Create a new Prim's algorithm. The value of the flag attribute is true for the tree edges and false for the non-tree edges.

Parameters:

weightAttribute - attribute used to compare edges

flagAttribute - attribute used to set if an edge is in the spanning tree

Prim

public Prim(java.lang.String flagAttribute,
            java.lang.Object flagOn,
            java.lang.Object flagOff)

Create a new Prim's algorithm. Uses the default weight attribute.

Parameters:

flagAttribute - attribute used to set if an edge is in the spanning tree

flagOn - value of the flagAttribute if edge is in the spanning tree

flagOff - value of the flagAttribute if edge is not in the spanning tree

Prim

public Prim(java.lang.String weightAttribute,
            java.lang.String flagAttribute,
            java.lang.Object flagOn,
            java.lang.Object flagOff)

Create a new Prim's algorithm.

Parameters:

weightAttribute - attribute used to compare edges

flagAttribute - attribute used to set if an edge is in the spanning tree

flagOn - value of the flagAttribute if edge is in the spanning tree

flagOff - value of the flagAttribute if edge is not in the spanning tree

Method Detail

defaultResult

public java.lang.String defaultResult()

Overrides:

defaultResult in class Kruskal