ec.exchange
Class InterPopulationExchange

java.lang.Object
  extended by ec.Exchanger
      extended by ec.exchange.InterPopulationExchange
All Implemented Interfaces:
Setup, Singleton, java.io.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
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
base.subpop.n.mod
int >= 1
The number of generations that subpopulation #n waits between sending emigrants
base.subpop.n.start
int >= 0
The generation when subpopulation #n begins sending emigrants
base.subpop.n.size
int >= 0
The number of emigrants sent at one time by generation #n
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

Version:
2.0
Author:
Liviu Panait & Sean Luke
See Also:
Serialized Form

Field Summary
 Parameter base
          My parameter base -- I need to keep this in order to help the server reinitialize contacts
 boolean chatty
           
static java.lang.String P_CHATTY
          Whether or not we're chatty
static java.lang.String P_DEST
          The prefix for destinations
static java.lang.String P_DEST_FOR_SUBPOP
          The number of destinations from current island
static java.lang.String P_MODULO
          The parameter for the modulo (how many generations should pass between consecutive sendings of individuals
static java.lang.String P_OFFSET
          How many generations to pass at the beginning of the evolution before the first emigration from the current subpopulation
static java.lang.String P_SELECT_METHOD
          The selection method for sending individuals to other islands
static java.lang.String P_SELECT_TO_DIE_METHOD
          The selection method for deciding individuals to be replaced by immigrants
static java.lang.String P_SIZE
          The number of emigrants to be sent
static java.lang.String P_SUBPOP
          The subpopulation delimiter
 
Constructor Summary
InterPopulationExchange()
           
 
Method Summary
 void closeContacts(EvolutionState state, int result)
          Closes contacts with other processes, if that's what you're doing.
 void initializeContacts(EvolutionState state)
          Initializes contacts with other processes, if that's what you're doing.
 Population postBreedingExchangePopulation(EvolutionState state)
          Performs exchanges after the population has been bred but before it has been evaluated, once every generation (or pseudogeneration).
 Population preBreedingExchangePopulation(EvolutionState state)
          Performs exchanges after the population has been evaluated but before it has been bred, once every generation (or pseudogeneration).
 void reinitializeContacts(EvolutionState state)
          Initializes contacts with other processes, if that's what you're doing.
 java.lang.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).
 void setup(EvolutionState state, Parameter _base)
          Sets up the object by reading it from the parameters stored in state, built off of the parameter base base.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

P_SUBPOP

public static final java.lang.String P_SUBPOP
The subpopulation delimiter

See Also:
Constant Field Values

P_MODULO

public static final java.lang.String P_MODULO
The parameter for the modulo (how many generations should pass between consecutive sendings of individuals

See Also:
Constant Field Values

P_SIZE

public static final java.lang.String P_SIZE
The number of emigrants to be sent

See Also:
Constant Field Values

P_OFFSET

public static final java.lang.String P_OFFSET
How many generations to pass at the beginning of the evolution before the first emigration from the current subpopulation

See Also:
Constant Field Values

P_DEST_FOR_SUBPOP

public static final java.lang.String P_DEST_FOR_SUBPOP
The number of destinations from current island

See Also:
Constant Field Values

P_DEST

public static final java.lang.String P_DEST
The prefix for destinations

See Also:
Constant Field Values

P_SELECT_METHOD

public static final java.lang.String P_SELECT_METHOD
The selection method for sending individuals to other islands

See Also:
Constant Field Values

P_SELECT_TO_DIE_METHOD

public static final java.lang.String P_SELECT_TO_DIE_METHOD
The selection method for deciding individuals to be replaced by immigrants

See Also:
Constant Field Values

P_CHATTY

public static final java.lang.String P_CHATTY
Whether or not we're chatty

See Also:
Constant Field Values

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 Detail

InterPopulationExchange

public InterPopulationExchange()
Method Detail

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.

Specified by:
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.

Specified by:
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 java.lang.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.

Specified by:
closeContacts in class Exchanger