Package ptolemy.graph.analysis.strategy

Class KarpCycleMeanStrategy

  • All Implemented Interfaces:
    Analyzer, CycleMeanAnalyzer, GraphAnalyzer
    public class KarpCycleMeanStrategy
extends CachedStrategy
implements CycleMeanAnalyzer
    An analyzer for computing the maximum/minimum cycle mean of a graph. This implementation uses the Karp's algorithm described in:

    A.Dasdan, R.K. Gupta, "Faster Maximum and Minimum Mean Cycle Algorithms for System Performance".

    Note that the mathematical definition of maximum cycle mean and maximum profit to cost are different, though some time the name "maximum cycle mean" is used to refer to the maximum profit to cost ratio.

    Since:
    Ptolemy II 4.0
    Version:
    $Id$
    Author:
    Shahrooz Shahparnia
    See Also:
    CycleMeanAnalysis
    Pt.AcceptedRating:
    Red (ssb)
    Pt.ProposedRating:
    Red (shahrooz)

    • Constructor Detail

      • KarpCycleMeanStrategy

        public KarpCycleMeanStrategy​(Graph graph,
                             ToDoubleMapping edgeLengths)
        Construct a maximum cycle mean analyzer for a given graph, using the Karp's algorithm.
        Parameters:
        graph - The given graph.
        edgeLengths - The lengths associated with the edges of the given graph.

    • Method Detail

      • cycle

        public java.util.List cycle()
        Return the nodes on the cycle that corresponds to the maximum/minimum cycle mean as an ordered list. If there is more than one cycle with the same maximal/minimal MCM, one of them is returned randomly, but the same cycle is returned by different invocations of the method, unless the graph changes. A call to maximumCycleMean() or minimumCycleMean() should precede a call to this method, in order to return a valid cycle.
        Specified by:
        cycle in interface CycleMeanAnalyzer
        Returns:
        The nodes on the cycle that corresponds to one of the maximum/minimum cycle means as an ordered list.

      • cycleMean

        public double cycleMean​(boolean maximum)
        Finds the cycle mean for a given directed graph. Strongly connected components are being considered separately. And the CycleMean is the maximum/minimum among them. When there are multiple edges between two nodes, the edge with the maximum/minimum weight is considered for the cycle that gives the maximum/minimum cycle mean.
        Parameters:
        maximum - True if the maximum cycle mean is requested.
        Returns:
        The maximum/minimum cycle mean.

      • maximumCycleMean

        public double maximumCycleMean()
        Return the maximum cycle mean.
        Specified by:
        maximumCycleMean in interface CycleMeanAnalyzer
        Returns:
        The maximum cycle mean value.

      • minimumCycleMean

        public double minimumCycleMean()
        Return minimum cycle mean.
        Specified by:
        minimumCycleMean in interface CycleMeanAnalyzer
        Returns:
        The minimum cycle mean value.

      • toString

        public java.lang.String toString()
        Return a description of the analyzer.
        Specified by:
        toString in interface Analyzer
        Overrides:
        toString in class CachedStrategy
        Returns:
        Return a description of the analyzer..

      • valid

        public boolean valid()
        Check for compatibility between the analysis and the given graph. A graph needs to be an instance of a DirectedGraph and cyclic in order to have a cycle mean. In addition the given object should be the same graph associated with this analyzer.
        Specified by:
        valid in interface Analyzer
        Returns:
        True if the graph is a directed and cyclic graph.

      • _compute

        protected java.lang.Object _compute()
        Description copied from class: CachedStrategy
        Perform the graph analysis and return the resulting value. Upon entry, CachedStrategy.getCachedResult() provides the result of the previous invocation of the analysis; this value can be used, for example, to facilitate incremental analyses. This method just returns null, and will typically be overridden in each derived class to perform the appropriate graph analysis.
        Overrides:
        _compute in class CachedStrategy
        Returns:
        The results of the graph analysis. In this base class, null is returned.