Package ec.exchange

Class InterPopulationExchange

java.lang.Object
ec.Exchanger
ec.exchange.InterPopulationExchange
All Implemented Interfaces:
Setup, Singleton, Serializable
public class InterPopulationExchange extends Exchanger
InterPopulationExchange is an Exchanger which implements a simple exchanger between subpopulations. IterPopulationExchange uses an arbitrary graph topology for migrating individuals from subpopulations. The assumption is that all subpopulations have the same representation and same task to solve, otherwise the exchange between subpopulations does not make much sense.

InterPopulationExchange has a topology which is similar to the one used by IslandExchange. Every few generations, a subpopulation will send some number of individuals to other subpopulations. Since all subpopulations evolve at the same generational speed, this is a synchronous procedure (IslandExchange instead is asynchronous by default, though you can change it to synchronous).

Individuals are sent from a subpopulation prior to breeding. They are stored in a waiting area until after all subpopulations have bred; thereafter they are added into the new subpopulation. This means that the subpopulation order doesn't matter. Also note that it means that some individuals will be created during breeding, and immediately killed to make way for the migrants. A little wasteful, we know, but it's simpler that way.

Parameters

base.chatty
boolean, default = true		 Should we be verbose or silent about our exchanges?

Note: For each subpopulation in your population, there must be one exch.subpop... declaration set.

base.subpop.n.select
classname, inherits and != ec.SelectionMethod		 The selection method used by subpopulation #n for picking migrants to emigrate to other subpopulations. If not set, uses the default parameter below.
base.select
classname, inherits and != ec.SelectionMethod		 server: Default parameter: the selection method used by a given subpopulation for picking migrants to emigrate to other subpopulations.
base.subpop.n.select-to-die
classname, inherits and != ec.SelectionMethod (Default is random selection)		 The selection method used by subpopulation #n for picking individuals to be replaced by migrants. If not set, uses the default parameter below.
base.select-to-die
classname, inherits and != ec.SelectionMethod (Default is random selection)		 server: Default parameter: the selection method used by a given subpopulation for picking individuals to be replaced by migrants.
base.subpop.n.mod
int >= 1		 The number of generations that subpopulation #n waits between sending emigrants. If not set, uses the default parameter below.
base.mod
int >= 1		 server: Default parameter: the number of generations that a given subpopulation waits between sending emigrants.
base.subpop.n.start
int >= 0		 The generation when subpopulation #n begins sending emigrants. If not set, uses the default parameter below.
base.start
int >= 0		 server: Default parameter: the generation when a given subpopulation begins sending emigrants.
base.subpop.n.size
int >= 0		 The number of emigrants sent at one time by generation #n. If not set, uses the default parameter below.
base.subpop.n.num-dest
int >= 0		 The number of destination subpopulations for this subpopulation.
base.subpop.n.dest.m
int >= 0		 Subpopulation #n's destination #m is this subpopulation.

Parameter bases

base.subpop.n.select
selection method for subpopulation #n's migrants
See Also:

  • Field Details

    • P_SUBPOP

      public static final String P_SUBPOP
      The subpopulation delimiter
      See Also:

    • P_MODULO

      public static final String P_MODULO
      The parameter for the modulo (how many generations should pass between consecutive sendings of individuals
      See Also:

    • P_SIZE

      public static final String P_SIZE
      The number of emigrants to be sent
      See Also:

    • P_OFFSET

      public static final String P_OFFSET
      How many generations to pass at the beginning of the evolution before the first emigration from the current subpopulation
      See Also:

    • P_DEST_FOR_SUBPOP

      public static final String P_DEST_FOR_SUBPOP
      The number of destinations from current island
      See Also:

    • P_DEST

      public static final String P_DEST
      The prefix for destinations
      See Also:

    • P_SELECT_METHOD

      public static final String P_SELECT_METHOD
      The selection method for sending individuals to other islands
      See Also:

    • P_SELECT_TO_DIE_METHOD

      public static final String P_SELECT_TO_DIE_METHOD
      The selection method for deciding individuals to be replaced by immigrants
      See Also:

    • P_CHATTY

      public static final String P_CHATTY
      Whether or not we're chatty
      See Also:

    • base

      public Parameter base
      My parameter base -- I need to keep this in order to help the server reinitialize contacts

    • chatty

      public boolean chatty

  • Constructor Details

    • InterPopulationExchange

      public InterPopulationExchange()

  • Method Details

    • setup

      public void setup(EvolutionState state, Parameter _base)
      Description copied from interface: Setup
      Sets up the object by reading it from the parameters stored in state, built off of the parameter base base. If an ancestor implements this method, be sure to call super.setup(state,base); before you do anything else.

    • initializeContacts

      public void initializeContacts(EvolutionState state)
      Initializes contacts with other processes, if that's what you're doing. Called at the beginning of an evolutionary run, before a population is set up. It doesn't do anything, as this exchanger works on only 1 computer.
      Overrides:
      initializeContacts in class Exchanger

    • reinitializeContacts

      public void reinitializeContacts(EvolutionState state)
      Initializes contacts with other processes, if that's what you're doing. Called after restarting from a checkpoint. It doesn't do anything, as this exchanger works on only 1 computer.
      Overrides:
      reinitializeContacts in class Exchanger

    • preBreedingExchangePopulation

      public Population preBreedingExchangePopulation(EvolutionState state)
      Description copied from class: Exchanger
      Performs exchanges after the population has been evaluated but before it has been bred, once every generation (or pseudogeneration).
      Specified by:
      preBreedingExchangePopulation in class Exchanger

    • postBreedingExchangePopulation

      public Population postBreedingExchangePopulation(EvolutionState state)
      Description copied from class: Exchanger
      Performs exchanges after the population has been bred but before it has been evaluated, once every generation (or pseudogeneration).
      Specified by:
      postBreedingExchangePopulation in class Exchanger

    • runComplete

      public String runComplete(EvolutionState state)
      Called after preBreedingExchangePopulation(...) to evaluate whether or not the exchanger wishes the run to shut down (with ec.EvolutionState.R_FAILURE). This would happen for two reasons. First, another process might have found an ideal individual and the global run is now over. Second, some network or operating system error may have occurred and the system needs to be shut down gracefully. This function does not return a String as soon as it wants to exit (another island found the perfect individual, or couldn't connect to the server). Instead, it sets a flag, called message, to remember next time to exit. This is due to a need for a graceful shutdown, where checkpoints are working properly and save all needed information.
      Specified by:
      runComplete in class Exchanger

    • closeContacts

      public void closeContacts(EvolutionState state, int result)
      Closes contacts with other processes, if that's what you're doing. Called at the end of an evolutionary run. result is either ec.EvolutionState.R_SUCCESS or ec.EvolutionState.R_FAILURE, indicating whether or not an ideal individual was found.
      Overrides:
      closeContacts in class Exchanger