org.apache.mahout.ep

Class EvolutionaryProcess<T extends Payload<U>,U>

java.lang.Object

org.apache.mahout.ep.EvolutionaryProcess<T,U>

Type Parameters:

T - The payload class.

All Implemented Interfaces:

Closeable, AutoCloseable, org.apache.hadoop.io.Writable

public class EvolutionaryProcess<T extends Payload<U>,U>
extends Object
implements org.apache.hadoop.io.Writable, Closeable

Allows evolutionary optimization where the state function can't be easily packaged for the optimizer to execute. A good example of this is with on-line learning where optimizing the learning parameters is desirable. We would like to pass training examples to the learning algorithms, but we definitely want to do the training in multiple threads and then after several training steps, we want to do a selection and mutation step. In such a case, it is highly desirable to leave most of the control flow in the hands of our caller. As such, this class provides three functions,

• Storage of the evolutionary state. The state variables have payloads which can be anything that implements Payload.
• Threaded execution of a single operation on each of the members of the population being evolved. In the on-line learning example, this is used for training all of the classifiers in the population.
• Propagating mutations of the most successful members of the population. This propagation involves copying the state and the payload and then updating the payload after mutation of the evolutionary state.

The State class that we use for storing the state of each member of the population also provides parameter mapping. Check out Mapping and State for more info.

See Also:

Mapping, Payload, State

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	EvolutionaryProcess.Function<T>

Constructor Summary

Constructors

Constructor and Description
EvolutionaryProcess()
EvolutionaryProcess(int threadCount, int populationSize, State<T,U> seed) Creates an evolutionary optimization framework with specified threadiness, population size and initial state.

Method Summary

Methods

Modifier and Type	Method and Description
void	add(State<T,U> value)
void	close()
List<State<T,U>>	getPopulation()
int	getPopulationSize()
int	getThreadCount()
void	mutatePopulation(int survivors) Nuke all but a few of the current population and then repopulate with variants of the survivors.
State<T,U>	parallelDo(EvolutionaryProcess.Function<Payload<U>> fn) Execute an operation on all of the members of the population with many threads.
void	readFields(DataInput input)
void	setThreadCount(int threadCount)
void	write(DataOutput out)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

EvolutionaryProcess

public EvolutionaryProcess()

EvolutionaryProcess

public EvolutionaryProcess(int threadCount,
                   int populationSize,
                   State<T,U> seed)

Creates an evolutionary optimization framework with specified threadiness, population size and initial state.

Parameters:

threadCount - How many threads to use in parallelDo

populationSize - How large a population to use

seed - An initial population member

Method Detail

add

public void add(State<T,U> value)

mutatePopulation

public void mutatePopulation(int survivors)

Nuke all but a few of the current population and then repopulate with variants of the survivors.

Parameters:

survivors - How many survivors we want to keep.

parallelDo

public State<T,U> parallelDo(EvolutionaryProcess.Function<Payload<U>> fn)
                                         throws InterruptedException,
                                                ExecutionException

Execute an operation on all of the members of the population with many threads. The return value is taken as the current fitness of the corresponding member.

Parameters:

fn - What to do on each member. Gets payload and the mapped parameters as args.

Returns:

The member of the population with the best fitness.

Throws:

InterruptedException - Shouldn't happen.

ExecutionException - If fn throws an exception, that exception will be collected and rethrown nested in an ExecutionException.

setThreadCount

public void setThreadCount(int threadCount)

getThreadCount

public int getThreadCount()

getPopulationSize

public int getPopulationSize()

getPopulation

public List<State<T,U>> getPopulation()

close

public void close()

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

write

public void write(DataOutput out)
           throws IOException

Specified by:

write in interface org.apache.hadoop.io.Writable

Throws:

IOException

readFields

public void readFields(DataInput input)
                throws IOException

Specified by:

readFields in interface org.apache.hadoop.io.Writable

Throws:

IOException