## Class HowardMinimumMeanCycle<V,​E>

• java.lang.Object
• org.jgrapht.alg.cycle.HowardMinimumMeanCycle<V,​E>
• Type Parameters:
V - graph vertex type
E - graph edge type
All Implemented Interfaces:
MinimumCycleMeanAlgorithm<V,​E>

public class HowardMinimumMeanCycle<V,​E>
extends java.lang.Object
implements MinimumCycleMeanAlgorithm<V,​E>
Implementation of Howards algorithm for finding minimum cycle mean in a graph.

The algorithm is described in the article: Ali Dasdan, Sandy S. Irani, and Rajesh K. Gupta. 1999. Efficient algorithms for optimum cycle mean and optimum cost to time ratio problems. In Proceedings of the 36th annual ACM/IEEE Design Automation Conference (DAC ’99). Association for Computing Machinery, New York, NY, USA, 37–42. DOI:https://doi.org/10.1145/309847.309862

Firstly, the graph is divided into strongly connected components. The minimum cycle mean is then computed as the globally minimum cycle mean over all components. In the process the necessary information is recorded to be able to reconstruct the cycle with minimum mean.

The computations are divided into iterations. In each iteration the algorithm tries to update current minimum cycle mean value. There is a possibility to limit the total number of iteration via a constructor parameter.

Author:
Semen Chudakov
• ### Constructor Summary

Constructors
Constructor Description
HowardMinimumMeanCycle​(Graph<V,​E> graph)
Constructs an instance of the algorithm for the given graph.
HowardMinimumMeanCycle​(Graph<V,​E> graph, int maximumIterations)
Constructs an instance of the algorithm for the given graph and maximumIterations.
HowardMinimumMeanCycle​(Graph<V,​E> graph, int maximumIterations, StrongConnectivityAlgorithm<V,​E> strongConnectivityAlgorithm, double toleranceEpsilon)
Constructs an instance of the algorithm for the given graph, maximumIterations, strongConnectivityAlgorithm and toleranceEpsilon.
• ### Method Summary

All Methods
Modifier and Type Method Description
GraphPath<V,​E> getCycle()
Computes cycle with minimum mean.
double getCycleMean()
Computes minimum mean among all cycle.
• ### Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
• ### Constructor Detail

• #### HowardMinimumMeanCycle

public HowardMinimumMeanCycle​(Graph<V,​E> graph)
Constructs an instance of the algorithm for the given graph.
Parameters:
graph - graph
• #### HowardMinimumMeanCycle

public HowardMinimumMeanCycle​(Graph<V,​E> graph,
int maximumIterations)
Constructs an instance of the algorithm for the given graph and maximumIterations.
Parameters:
graph - graph
maximumIterations - maximum number of iterations
• #### HowardMinimumMeanCycle

public HowardMinimumMeanCycle​(Graph<V,​E> graph,
int maximumIterations,
StrongConnectivityAlgorithm<V,​E> strongConnectivityAlgorithm,
double toleranceEpsilon)
Constructs an instance of the algorithm for the given graph, maximumIterations, strongConnectivityAlgorithm and toleranceEpsilon.
Parameters:
graph - graph
maximumIterations - maximum number of iterations
strongConnectivityAlgorithm - algorithm to compute strongly connected components
toleranceEpsilon - tolerance to compare floating point numbers
• ### Method Detail

• #### getCycleMean

public double getCycleMean()
Computes minimum mean among all cycle. Returns Double.POSITIVE_INFINITY if no cycle has been found.
Specified by:
getCycleMean in interface MinimumCycleMeanAlgorithm<V,​E>
Returns:
minimum mean
• #### getCycle

public GraphPath<V,​E> getCycle()
Computes cycle with minimum mean. Returns $null$ if no cycle has been found.
Specified by:
getCycle in interface MinimumCycleMeanAlgorithm<V,​E>`
Returns:
cycle with minimum mean