Package org.cloudsimplus.heuristics

Interface Heuristic<S extends HeuristicSolution<?>>

Type Parameters:
S - the class of solutions the heuristic will deal with
All Known Subinterfaces:
CloudletToVmMappingHeuristic
All Known Implementing Classes:
CloudletToVmMappingSimulatedAnnealing, HeuristicAbstract, SimulatedAnnealingAbstract
public interface Heuristic<S extends HeuristicSolution<?>>

Provides the methods to be used for implementation of heuristics to find solution for complex problems where the solution space to search is large. These problems are usually NP-Hard ones which the time to find a solution increases, for instance, in exponential time. Such problems can be, for instance, mapping a set of VMs to existing Hosts or mapping a set of Cloudlets to VMs. A heuristic implementation thus provides an approximation of an optimal solution (a suboptimal solution).

Different heuristic can be implemented, such as Tabu search, Simulated annealing, Hill climbing or Ant colony optimization, to name a few.

Since:
CloudSim Plus 1.0
Author:
Manoel Campos da Silva Filho

  • Field Details

    • LOGGER

      static final org.slf4j.Logger LOGGER

    • NULL

      static final Heuristic NULL
      A property that implements the Null Object Design Pattern for Heuristic objects.

  • Method Details

    • getAcceptanceProbability

      double getAcceptanceProbability()
      Computes the acceptance probability to define if a neighbor solution has to be accepted or not, compared to the getBestSolutionSoFar().
      Returns:
      the acceptance probability, in scale from [0 to 1] where: 0 is to maintain the current solution; 1 is to accept the neighbor solution; intermediate values defines the probability that the neighbor solution will be randomly accepted.

    • getRandomValue

      int getRandomValue(int maxValue)
      Gets a random number between 0 (inclusive) and maxValue (exclusive).
      Parameters:
      maxValue - the max value to get a random number (exclusive)
      Returns:
      the random number

    • isToStopSearch

      boolean isToStopSearch()
      Checks if the solution search can be stopped.
      Returns:
      true if the solution search can be stopped, false otherwise.

    • getInitialSolution

      S getInitialSolution()
      Gets the initial solution that the heuristic will start from in order to try to improve it. If not initial solution was generated yet, one should be randomly generated.
      Returns:
      the initial randomly generated solution

    • getNeighborSolution

      S getNeighborSolution()
      Returns:
      latest neighbor solution created
      See Also:

    • createNeighbor

      S createNeighbor(S source)
      Creates a neighbor solution cloning a source one and randomly changing some of its values. A neighbor solution is one that is close to the current solution and has just little changes.
      Parameters:
      source - the source to create a neighbor solution
      Returns:
      the cloned and randomly changed solution that represents a neighbor solution

    • getBestSolutionSoFar

      S getBestSolutionSoFar()
      Returns:
      best solution found out up to now

    • getSearchesByIteration

      int getSearchesByIteration()
      Returns:
      the number of times a neighbor solution will be searched at each iteration of the solution find.

    • setSearchesByIteration

      void setSearchesByIteration(int numberOfNeighborhoodSearches)
      Sets the number of times a neighbor solution will be searched at each iteration of the solution find.
      Parameters:
      numberOfNeighborhoodSearches - number of neighbor searches to perform at each iteration

    • solve

      S solve()
      Starts the heuristic to find a suboptimal solution. After the method finishes, you can call the getBestSolutionSoFar() to get the final solution.
      Returns:
      the final solution
      See Also:

    • getSolveTime

      double getSolveTime()
      Returns:
      the time taken to finish the solution search (in seconds).
      See Also: