/* Analysis to check if a cyclic directed graph has a negative-length cycle.
Copyright (c) 2003-2005 The University of Maryland. All rights reserved.
Permission is hereby granted, without written agreement and without
license or royalty fees, to use, copy, modify, and distribute this
software and its documentation for any purpose, provided that the above
copyright notice and the following two paragraphs appear in all copies
of this software.
IN NO EVENT SHALL THE UNIVERSITY OF MARYLAND BE LIABLE TO ANY PARTY
FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
THE UNIVERSITY OF MARYLAND HAS BEEN ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
THE UNIVERSITY OF MARYLAND SPECIFICALLY DISCLAIMS ANY WARRANTIES,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
MARYLAND HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES,
ENHANCEMENTS, OR MODIFICATIONS.
*/
package ptolemy.graph.analysis;
import ptolemy.graph.Graph;
import ptolemy.graph.analysis.analyzer.Analyzer;
import ptolemy.graph.analysis.analyzer.NegativeLengthCycleAnalyzer;
import ptolemy.graph.analysis.strategy.FloydWarshallNegativeLengthCycleStrategy;
import ptolemy.graph.mapping.ToDoubleMapping;
//////////////////////////////////////////////////////////////////////////
//// NegativeLengthCycleAnalysis
/**
Analysis to check if a cyclic directed graph has a negative-length cycle.
A negative-length cycle is a cycle in which the sum of all the values associated
with the edges of the cycle is negative. In a graph with multiple edges between
two nodes the one with the smallest associated value is being used to check for
the existence of negative cycles.
<p>
@since Ptolemy II 4.0
@Pt.ProposedRating Red (shahrooz)
@Pt.AcceptedRating Red (ssb)
@author Shahrooz Shahparnia
@version $Id$
*/
public class NegativeLengthCycleAnalysis extends Analysis {
/** Construct an instance of this class using a default analyzer.
* The default analyzer runs in O(N^3) in which N is the number of nodes.
*
* @param graph The given graph.
* @param edgeLengths The lengths associated with the edges of the graph.
*/
public NegativeLengthCycleAnalysis(Graph graph, ToDoubleMapping edgeLengths) {
super(new FloydWarshallNegativeLengthCycleStrategy(graph, edgeLengths));
}
/** Construct an instance of this class using a given analyzer.
*
* @param analyzer The given analyzer.
*/
public NegativeLengthCycleAnalysis(NegativeLengthCycleAnalyzer analyzer) {
super(analyzer);
}
///////////////////////////////////////////////////////////////////
//// public methods ////
/** Return true if a negative cycle exists in the graph under analysis.
*
* @return True if the graph has a negative cycle.
*/
public boolean hasNegativeLengthCycle() {
return ((NegativeLengthCycleAnalyzer) analyzer())
.hasNegativeLengthCycle();
}
/** Return a description of the analysis and the associated analyzer.
*
* @return A description of the analysis and the associated analyzer.
*/
public String toString() {
return "Negative-length cycle analysis using the following analyzer:\n"
+ analyzer().toString();
}
/** Check if a given analyzer is compatible with this analysis.
* In other words if it is possible to use it to compute the computation
* associated with this analysis.
*
* @param analyzer The given analyzer.
* @return True if the given analyzer is valid for this analysis.
*/
public boolean validAnalyzerInterface(Analyzer analyzer) {
return analyzer instanceof NegativeLengthCycleAnalyzer;
}
}