Class JGraphAlgebra

java.lang.Object
com.jgraph.algebra.JGraphAlgebra
public class JGraphAlgebra extends Object
A singleton class that provides algorithms for graphs. Assume the following variable for the following examples:
JGraphDistanceCostFunction(graph.getGraphLayoutCache());
JGraphFacade facade = new JGraphFacade(graph);
Object[] v = facade.getVertices().toArray();
Object[] e = facade.getEdges().toArray();
JGraphAlgebra alg = JGraphAlgebra.getSharedInstance();

Shortest Path (Dijkstra)

For example, to find the shortest path between the first and the second selected cell in a graph use the following code:

Object[] path = alg.getShortestPath(graph.getModel(), sourceVertex, targetVertex, cf, v.length, true)

Minimum Spanning Tree

This algorithm finds the set of edges with the minimal length that connect all vertices. This algorithm can be used as follows:
Prim
alg.getMinimumSpanningTree(graph.getModel(), v, cf, true))
Kruskal
alg.getMinimumSpanningTree(graph.getModel(), v, e, cf))

Connection Components

The union find may be used as follows to determine whether two cells are connected: boolean connected = uf.differ(vertex1, vertex2).
See Also:

  • Field Details

    • sharedInstance

      protected static JGraphAlgebra sharedInstance
      Holds the shared instance of this class.

  • Constructor Details

    • JGraphAlgebra

      protected JGraphAlgebra()
      Subclassers may override to provide special union find and priority queue datastructures.

  • Method Details

    • getSharedInstance

      public static JGraphAlgebra getSharedInstance()
      Returns:
      Returns the sharedInstance.

    • setSharedInstance

      public static void setSharedInstance(JGraphAlgebra sharedInstance)
      Sets the shared instance of this class.
      Parameters:
      sharedInstance - The sharedInstance to set.

    • getShortestPath

      public Object[] getShortestPath(GraphModel model, Object from, Object to, JGraphCostFunction cf, int steps, boolean directed)
      Returns the shortest path between two cells or their descendants represented as an array of edges in order of traversal.
      This implementation is based on the Dijkstra algorithm.
      Parameters:
      model - the model that defines the graph structure
      from - the source port or vertex
      to - the target port or vertex (aka. sink)
      cf - the cost function that defines the edge length
      steps - the maximum number of edges to traverse
      directed - if edge directions should be taken into account
      Returns:
      Returns the shortest path as an array of edges
      See Also:

    • getMinimumSpanningTree

      public Object[] getMinimumSpanningTree(GraphModel model, Object[] v, JGraphCostFunction cf, boolean directed)
      Returns the minimum spanning tree (MST) for the graph defined by G=(E,V). The MST is defined as the set of all vertices with minimal lengths that forms no cycles in G.
      This implementation is based on the algorihm by Prim-Jarnik. It uses O(|E|+|V|log|V|) time when used with a Fibonacci heap and a graph whith a double linked-list datastructure, as is the case with the default implementation.
      Parameters:
      model - the model that describes the graph
      v - the vertices of the graph
      cf - the cost function that defines the edge length
      Returns:
      Returns the MST as an array of edges
      See Also:

    • getMinimumSpanningTree

      public Object[] getMinimumSpanningTree(GraphModel model, Object[] v, Object[] e, JGraphCostFunction cf)
      Returns the minimum spanning tree (MST) for the graph defined by G=(E,V). The MST is defined as the set of all vertices with minimal lenths that forms no cycles in G.
      This implementation is based on the algorihm by Kruskal. It uses O(|E|log|E|)=O(|E|log|V|) time for sorting the edges, O(|V|) create sets, O(|E|) find and O(|V|) union calls on the union find structure, thus yielding no more than O(|E|log|V|) steps. For a faster implementatin
      Parameters:
      model - the model that describes the graph
      v - the vertices of the graph
      e - the edges of the graph
      cf - the cost function that defines the edge length
      Returns:
      Returns the MST as an array of edges
      See Also:

    • getConnectionComponents

      public JGraphUnionFind getConnectionComponents(GraphModel model, Object[] v, Object[] e)
      Returns a union find structure representing the connection components of G=(E,V).
      Parameters:
      model - the model that describes the graph
      v - the vertices of the graph
      e - the edges of the graph
      Returns:
      Returns the connection components in G=(E,V)
      See Also:

    • sort

      public List sort(Object[] cells, JGraphCostFunction cf)
      Returns a sorted set for cells with respect to cf.
      Parameters:
      cells - the cells to sort
      cf - the cost function that defines the order
      Returns:
      Returns an ordered set of cells wrt. cf

    • sum

      public double sum(Object[] cells, JGraphCostFunction cf)
      Returns the sum of all cost for cells with respect to cf.
      Parameters:
      cells - the cells to use for the sum
      cf - the cost function that defines the costs
      Returns:
      Returns the sum of all cell cost

    • createUnionFind

      protected JGraphUnionFind createUnionFind(Object[] v)
      Hook for subclassers to provide a custom union find structure.
      Parameters:
      v - the array of all elements
      Returns:
      Returns a union find structure for v

    • createPriorityQueue

      protected JGraphFibonacciHeap createPriorityQueue()
      Hook for subclassers to provide a custom fibonacci heap.