public class MutateDemotePipeline extends GPBreedingPipeline
MutateDemotePipeline tries picks a random tree, then picks randomly from all the demotable nodes in the tree, and demotes one. If its chosen tree has no demotable nodes, or demoting its chosen demotable node would make the tree too deep, it repeats the choose-tree-then-choose-node process. If after tries times it has failed to find a valid tree and demotable node, it gives up and simply copies the individual.
"Demotion" means to take a node n and insert a new node m between n and n's parent. n becomes a child of m; the place where it becomes a child is determined at random from all the type-compatible slots of m. The other child slots of m are filled with randomly-generated terminals. Chellapilla's version of the algorithm always places n in child slot 0 of m. Because this would be unneccessarily restrictive on strong typing, MutateDemotePipeline instead picks the slot at random from all available valid choices.
A "Demotable" node means a node which is capable of demotion given the existing function set. In general to demote a node foo, there must exist in the function set a nonterminal whose return type is type-compatible with the child slot foo holds in its parent; this nonterminal must also have a child slot which is type-compatible with foo's return type.
This method is very expensive in searching nodes for "demotability". However, if the number of types is 1 (the GP run is typeless) then the type-constraint-checking code is bypassed and the method runs a little faster.
Typical Number of Individuals Produced Per produce(...) call
...as many as the source produces
Number of Sources
1
Parameters
base.tries int >= 1 |
(number of times to try finding valid pairs of nodes) |
base.maxdepth int >= 1 |
(maximum valid depth of a mutated tree) |
base.tree.0 0 < int < (num trees in individuals), if exists |
(tree chosen for mutation; if parameter doesn't exist, tree is picked at random) |
Default Base
gp.breed.mutate-demote
Modifier and Type | Field and Description |
---|---|
private GPNode |
demotableNode |
(package private) int |
maxDepth
The maximum depth of a mutated tree
|
static int |
NUM_SOURCES |
(package private) int |
numTries
The number of times the pipeline tries to build a valid mutated
tree before it gives up and just passes on the original
|
static String |
P_MAXDEPTH |
static String |
P_MUTATEDEMOTE |
static String |
P_NUM_TRIES |
(package private) int |
tree
Is our tree fixed? If not, this is -1
|
P_NODESELECTOR, P_TREE, TREE_UNFIXED
DYNAMIC_SOURCES, likelihood, mybase, P_LIKELIHOOD, P_NUMSOURCES, P_SOURCE, sources, V_SAME, V_STUB
NO_PROBABILITY, P_PROB, probability
Constructor and Description |
---|
MutateDemotePipeline() |
Modifier and Type | Method and Description |
---|---|
private void |
_demoteSomething(GPNode node,
EvolutionState state,
int thread,
GPFunctionSet set) |
private void |
_demoteSomethingTypeless(GPNode node,
EvolutionState state,
int thread,
GPFunctionSet set) |
private int |
_numDemotableNodes(GPInitializer initializer,
GPNode root,
int soFar,
GPFunctionSet set) |
private int |
_pickDemotableNode(GPInitializer initializer,
GPNode root,
int num,
GPFunctionSet set) |
Parameter |
defaultBase()
Returns the default base for this prototype.
|
private boolean |
demotable(GPInitializer initializer,
GPNode node,
GPFunctionSet set) |
private void |
demoteSomething(GPNode node,
EvolutionState state,
int thread,
GPFunctionSet set) |
private int |
numDemotableNodes(GPInitializer initializer,
GPNode root,
int soFar,
GPFunctionSet set) |
int |
numSources()
Returns the number of sources to this pipeline.
|
private int |
pickDemotableNode(GPInitializer initializer,
GPNode root,
int num,
GPFunctionSet set) |
int |
produce(int min,
int max,
int subpopulation,
ArrayList<Individual> inds,
EvolutionState state,
int thread,
HashMap<String,Object> misc)
Produces n individuals from the given subpopulation
and puts them into inds[start...start+n-1],
where n = Min(Max(q,min),max), where q is the "typical" number of
individuals the BreedingSource produces in one shot, and returns
n.
|
void |
setup(EvolutionState state,
Parameter base)
Sets up the BreedingPipeline.
|
private boolean |
verifyPoint(GPNode inner1)
Returns true if inner1's depth + atdepth +1 is within the depth bounds
|
produces
clone, fillStubs, finishProducing, individualReplaced, maxChildProduction, minChildProduction, preparePipeline, prepareToProduce, sourcesAreProperForm, typicalIndsProduced
getProbability, pickRandom, setProbability, setupProbabilities
public static final String P_MUTATEDEMOTE
public static final String P_NUM_TRIES
public static final String P_MAXDEPTH
public static final int NUM_SOURCES
int numTries
int maxDepth
int tree
private GPNode demotableNode
public Parameter defaultBase()
Prototype
public int numSources()
BreedingPipeline
numSources
in class BreedingPipeline
public void setup(EvolutionState state, Parameter base)
BreedingSource
The most common modification is to normalize it with some other set of probabilities, then set all of them up in increasing summation; this allows the use of the fast static BreedingSource-picking utility method, BreedingSource.pickRandom(...). In order to use this method, for example, if four breeding source probabilities are {0.3, 0.2, 0.1, 0.4}, then they should get normalized and summed by the outside owners as: {0.3, 0.5, 0.6, 1.0}.
setup
in interface Prototype
setup
in interface Setup
setup
in class BreedingPipeline
Prototype.setup(EvolutionState,Parameter)
private boolean demotable(GPInitializer initializer, GPNode node, GPFunctionSet set)
private void demoteSomething(GPNode node, EvolutionState state, int thread, GPFunctionSet set)
private void _demoteSomething(GPNode node, EvolutionState state, int thread, GPFunctionSet set)
private void _demoteSomethingTypeless(GPNode node, EvolutionState state, int thread, GPFunctionSet set)
private int numDemotableNodes(GPInitializer initializer, GPNode root, int soFar, GPFunctionSet set)
private int _numDemotableNodes(GPInitializer initializer, GPNode root, int soFar, GPFunctionSet set)
private int pickDemotableNode(GPInitializer initializer, GPNode root, int num, GPFunctionSet set)
private int _pickDemotableNode(GPInitializer initializer, GPNode root, int num, GPFunctionSet set)
private boolean verifyPoint(GPNode inner1)
public int produce(int min, int max, int subpopulation, ArrayList<Individual> inds, EvolutionState state, int thread, HashMap<String,Object> misc)
BreedingSource
produce
in class BreedingSource
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