org.apache.openjpa.lib.graph
Class DepthFirstAnalysis

java.lang.Object
  org.apache.openjpa.lib.graph.DepthFirstAnalysis

public class DepthFirstAnalysis
extends Object

Performs a depth-first analysis of a given Graph, caching information about the graph's nodes and edges. See the DFS algorithm in the book 'Introduction to Algorithms' by Cormen, Leiserson, and Rivest. The algorithm has been modified to group sibling nodes without connections together during the topological sort.

Since:

1.0.0

Author:

Abe White

Constructor Summary

DepthFirstAnalysis(Graph graph)
Constructor.

Method Summary

Collection	getEdges(int type) Return all edges of the given type.
int	getFinishedTime(Object node) Return the logical time that the given node was finished in the graph walk, or -1 if the node is not part of the graph.
List	getSortedNodes() Return the nodes in topologically-sorted order.
boolean	hasNoCycles() Test, if the analysis didn't find cycles.
void	setNodeComparator(Comparator comp) Set the comparator that should be used for ordering groups of nodes with the same dependencies.

Methods inherited from class java.lang.Object

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

Constructor Detail

DepthFirstAnalysis

public DepthFirstAnalysis(Graph graph)

Constructor. Performs the analysis on the given graph and caches the resulting information.

Method Detail

setNodeComparator

public void setNodeComparator(Comparator comp)

Set the comparator that should be used for ordering groups of nodes with the same dependencies.

getSortedNodes

public List getSortedNodes()

Return the nodes in topologically-sorted order. This is often used to order dependencies. If each graph edge (u, v) represents a dependency of v on u, then this method will return the nodes in the order that they should be evaluated to satisfy all dependencies. Of course, if the graph is cyclic (has back edges), then no such ordering is possible, though this method will still return the correct order as if edges creating the cycles did not exist.

getEdges

public Collection getEdges(int type)

Return all edges of the given type. This method can be used to discover all edges that cause cycles in the graph by passing it the Edge.TYPE_BACK or Edge.TYPE_FORWARD edge type.

getFinishedTime

public int getFinishedTime(Object node)

Return the logical time that the given node was finished in the graph walk, or -1 if the node is not part of the graph.

hasNoCycles

public boolean hasNoCycles()

Test, if the analysis didn't find cycles.