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Reorganize Ant Colony Optimization code around a new global/local upd…
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…ate rule paradigm. SimpleEvolutionState now calls hooks on Evaluator to trigger state updates, which pass calls along to the Species to handle things like Ant Colony System's global update.
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@SigmaX
SigmaX committed Aug 23, 2019
1 parent b50aa9e commit f188170
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Showing 13 changed files with 224 additions and 125 deletions.
23 changes: 23 additions & 0 deletions ecj/src/main/java/ec/Evaluator.java
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Expand Up @@ -135,4 +135,27 @@ public void closeContacts(EvolutionState state, int result)
{
p_problem.closeContacts(state,result);
}

/** Called to update some state by considering the current population.
*
* This are used by some algorithms to update additional state (stored the population's Species)
* beyond fitness values (ex. ACO's pheromone distributions).
*
* This method will typically just call a similar hook on a Species, where the actually state update occurs.*/
public void postEvaluationGlobalUpdate(EvolutionState state)
{
// Do nothing by default
}


/** Called to update some state by considering a single Individual.
*
* This are used by some algorithms to update additional state (stored the population's Species)
* beyond fitness values (ex. ACO's pheromone distributions).
*
* This method will typically just call a similar hook on a Species, where the actually state update occurs.*/
public void postEvaluationLocalUpdate(EvolutionState state, Individual ind, int subpop)
{
// Do nothing by default
}
}
24 changes: 24 additions & 0 deletions ecj/src/main/java/ec/Species.java
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Expand Up @@ -221,6 +221,30 @@ public void setup(final EvolutionState state, final Parameter base)
f_prototype = (Fitness) state.parameters.getInstanceForParameter( base.push(P_FITNESS),def.push(P_FITNESS), Fitness.class);
f_prototype.setup(state,base.push(P_FITNESS));
}

/** A hook for code that is run on every individual as soon as it is evaluated. This method does nothing unless it
* is override by a subclass.
*
* For example, an implementation of Ant Colony System might use this to apply a
* local pheromone update.
*
* @see ec.simple.SimpleEvaluator
*/
public void updateIndividual(final EvolutionState state, final Individual ind)
{
// Do nothing by default
}

/**
* A hook for code that is run on the entire subpopulation as soon as it has been evaluated.
*
* For example, an implementation of Ant System might use this to apply a global
* pheromone update. You can see how this method is used by having a look at SimpleEvaluator.
*/
public void updateSubpopulation(final EvolutionState state, final Subpopulation subpop)
{
// Do nothing by default
}
}


4 changes: 1 addition & 3 deletions ecj/src/main/java/ec/co/ConstructiveBreeder.java
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Original file line number Diff line number Diff line change
@@ -1,13 +1,11 @@
/*
Copyright 2017 by Sean Luke
Copyright 2019 by Sean Luke
Licensed under the Academic Free License version 3.0
See the file "LICENSE" for more information
*/
package ec.co;

import ec.*;
import ec.co.ConstructiveIndividual;
import ec.co.ConstructiveProblemForm;
import ec.util.Parameter;

/**
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71 changes: 46 additions & 25 deletions ecj/src/main/java/ec/co/ant/AntSpecies.java
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Original file line number Diff line number Diff line change
Expand Up @@ -9,14 +9,10 @@
import ec.Fitness;
import ec.Individual;
import ec.Species;
import static ec.Species.P_FITNESS;
import static ec.Species.P_INDIVIDUAL;
import ec.Subpopulation;
import ec.co.ConstructiveIndividual;
import ec.co.ConstructiveProblemForm;
import ec.util.Parameter;
import java.util.ArrayList;
import java.util.List;

/**
*
Expand All @@ -26,15 +22,17 @@ public class AntSpecies extends Species
{
public final static Parameter DEFAULT_BASE = new Parameter("constructive");
public final static String SPECIES_NAME = "constructive-species";

public final static String P_CONSTRUCTION_RULE = "construction-rule";
public final static String P_PHEROMONE_TABLE = "pheromone-table";
public final static String P_UPDATE_RULE = "update-rule";

public final static String P_LOCAL_UPDATE_RULE = "local-update-rule";

private ConstructionRule constructionRule;
private PheromoneTable pheromones;
private UpdateRule updateRule;

private UpdateRule localUpdateRule;

@Override
public void setup(final EvolutionState state, final Parameter base)
{
Expand All @@ -43,15 +41,24 @@ public void setup(final EvolutionState state, final Parameter base)
assert(base != null);
constructionRule = (ConstructionRule) state.parameters.getInstanceForParameter(base.push(P_CONSTRUCTION_RULE), null, ConstructionRule.class);
constructionRule.setup(state, base.push(P_CONSTRUCTION_RULE));

pheromones = (PheromoneTable) state.parameters.getInstanceForParameter(base.push(P_PHEROMONE_TABLE), null, PheromoneTable.class);
pheromones.setup(state, base.push(P_PHEROMONE_TABLE));

updateRule = (UpdateRule) state.parameters.getInstanceForParameter(base.push(P_UPDATE_RULE), null, UpdateRule.class);
updateRule.setup(state, base.push(P_UPDATE_RULE));

if (state.parameters.exists(base.push(P_UPDATE_RULE), null))
{
updateRule = (UpdateRule) state.parameters.getInstanceForParameter(base.push(P_UPDATE_RULE), null, UpdateRule.class);
updateRule.setup(state, base.push(P_UPDATE_RULE));
}

if (state.parameters.exists(base.push(P_LOCAL_UPDATE_RULE), null))
{
localUpdateRule = (UpdateRule) state.parameters.getInstanceForParameter(base.push(P_LOCAL_UPDATE_RULE), null, UpdateRule.class);
localUpdateRule.setup(state, base.push(P_LOCAL_UPDATE_RULE));
}
assert(repOK());
}

/** A custom setup method for Species that skips the initialization of the
* breeding pipeline. We call this in place of super.setup(), since this
* Species doesn't use a pipeline.
Expand All @@ -63,44 +70,58 @@ private void setupSuper(final EvolutionState state, final Parameter base)
Parameter def = defaultBase();
// load our individual prototype
i_prototype = (Individual)(state.parameters.getInstanceForParameter(
base.push(P_INDIVIDUAL),def.push(P_INDIVIDUAL),
Individual. class));
base.push(P_INDIVIDUAL),def.push(P_INDIVIDUAL),
Individual. class));
// set the species to me before setting up the individual, so they know who I am
i_prototype.species = this;
i_prototype.setup(state,base.push(P_INDIVIDUAL));

// load our fitness
f_prototype = (Fitness) state.parameters.getInstanceForParameter(
base.push(P_FITNESS),def.push(P_FITNESS),
Fitness.class);
base.push(P_FITNESS),def.push(P_FITNESS),
Fitness.class);
f_prototype.setup(state,base.push(P_FITNESS));
}

public void updatePheromones(final EvolutionState state, final Subpopulation population)

/** Apply a global update rule to the pheromone table.
*
* @param subpop The Subpopulation to use as the input of the global update. */
@Override
public void updateSubpopulation(final EvolutionState state, final Subpopulation subpop)
{
updateRule.updatePheromones(state, pheromones, population);
updateRule.updatePheromones(state, pheromones, subpop.individuals);
assert(repOK());
}


/** Apply a local update rule to the pheromone table.
*
* @param ind The Individual to use as the input of the local update. */
@Override
public void updateIndividual(final EvolutionState state, final Individual ind)
{
if (localUpdateRule != null)
localUpdateRule.updatePheromones(state, pheromones, new ArrayList() {{ add(ind); }});
}

@Override
public ConstructiveIndividual newIndividual(final EvolutionState state, final int thread)
{
assert(state != null);
assert(thread >= 0);

final ConstructiveIndividual ind = (ConstructiveIndividual)(super.newIndividual(state, thread));
assert(repOK());
return constructionRule.constructSolution(state, ind, pheromones, thread);
}

@Override
public Parameter defaultBase()
{
return DEFAULT_BASE.push(SPECIES_NAME);
}

/** Representation invariant, used for verification.
*
*
* @return true if the class is found to be in an erroneous state.
*/
public final boolean repOK()
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52 changes: 26 additions & 26 deletions ecj/src/main/java/ec/co/ant/AntSystemUpdateRule.java
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Original file line number Diff line number Diff line change
Expand Up @@ -30,7 +30,7 @@ public class AntSystemUpdateRule implements UpdateRule
public enum DepositRule { ANT_CYCLE, ANT_DENSITY, ANT_QUANTITY };
private DepositRule depositRule;
private double q;

@Override
public void setup(final EvolutionState state, final Parameter base)
{
Expand All @@ -46,72 +46,72 @@ public void setup(final EvolutionState state, final Parameter base)
if (depositString == null)
state.output.fatal(String.format("%s: missing required parameter '%s'.", this.getClass().getSimpleName(), base.push(P_DEPOSIT_RULE)));
try
{
{
depositString = depositString.replace('-', '_');
depositRule = DepositRule.valueOf(depositString);
}
}
catch (final NullPointerException e)
{
{
state.output.fatal(String.format("%s: invalid value '%s' found for parameter '%s'. Allowed values are %s.", this.getClass().getSimpleName(), depositString, base.push(P_DEPOSIT_RULE), Arrays.asList(DepositRule.values())));
}
}
catch (final IllegalArgumentException e)
{
{
state.output.fatal(String.format("%s: invalid value '%s' found for parameter '%s'. Allowed values are %s.", this.getClass().getSimpleName(), depositString, base.push(P_DEPOSIT_RULE), Arrays.asList(DepositRule.values())));
}
}
assert(repOK());
}

public double getDecayRate()
{
return decayRate;
}

public DepositRule getDepositRule()
{
return depositRule;
}

public double getQ()
{
return q;
}

@Override
public void updatePheromones(final EvolutionState state, final PheromoneTable pheromones, final Subpopulation subpop)
public void updatePheromones(final EvolutionState state, final PheromoneTable pheromones, final List individuals)
{
assert(pheromones != null);
assert(subpop != null);

assert(individuals != null);
assert(!individuals.isEmpty());

decayPheromones(state, pheromones);

final Map<Component, Double> contributions = new HashMap();
// Loop through every individual and record its pheremone contributions (scores) for each edge
for (final Individual o : subpop.individuals)
{
assert(o instanceof ConstructiveIndividual);
for (final Object o : individuals)
{
final ConstructiveIndividual ind = (ConstructiveIndividual) o;
assert(ind.size() > 0);
for (final Object oo : ind)
{
{
assert(oo instanceof Component);
final Component c = (Component) oo;
final double cPheromone = pheromoneContribution(ind, c);
if (contributions.containsKey(c))
contributions.put(c, contributions.get(c) + cPheromone);
else
contributions.put(c, cPheromone);
}
}
}
// Apply the new pheromones
for (final Component c : contributions.keySet())
{
{
final double oldPheromone = pheromones.get(state, c, 0); // Using thread 0 because we are in a single-threaded function
final double newPheromone = oldPheromone + contributions.get(c);
pheromones.set(c, newPheromone);
}
}
assert(repOK());
}

private void decayPheromones(final EvolutionState state, final PheromoneTable pheromones)
{
assert(state != null);
Expand All @@ -120,14 +120,14 @@ private void decayPheromones(final EvolutionState state, final PheromoneTable ph
for (final Component c : components)
pheromones.set(c, (1.0-decayRate)*pheromones.get(state, c, 0)); // Using thread 0 because we are in a single-threaded function
}

private double pheromoneContribution(final ConstructiveIndividual ind, final Component component)
{
assert(ind != null);
assert(component != null);
final double fitness = ind.fitness.fitness();
switch (depositRule)
{
{
case ANT_CYCLE:
assert(fitness > 0);
return q*fitness;
Expand All @@ -137,9 +137,9 @@ private double pheromoneContribution(final ConstructiveIndividual ind, final Com
return q*component.desirability();
default:
throw new IllegalStateException(String.format("%s: no deposit rule logic implemented for %s.", this.getClass().getSimpleName(), depositRule));
}
}
}

public final boolean repOK()
{
return P_DECAY_RATE != null
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