burlap.behavior.statehashing

Class DiscreteStateHashFactory

java.lang.Object

burlap.behavior.statehashing.DiscreteStateHashFactory

All Implemented Interfaces:

StateHashFactory

Direct Known Subclasses:

DiscreteMaskHashingFactory

public class DiscreteStateHashFactory
extends java.lang.Object
implements StateHashFactory

This hash factory will producing hash codes that are unique for discrete OO-MDP domains. It should *not* be used with continuous domains nor relational domains. If the default constructor is called and no other methods are specified, then the state hash code will be computed with respect to all attributes of every object instance. It is not uncommon for tasks in certain domains to make the values for certain objects constant. For instance, consider a goal location which will always be the in same location for all states of a task. In such situations, the attributes of constant objects provide no information about the specific state and computing a hash code with respect to its values is wasted computation time. To make hash code computation more efficient, the user can also specify which attributes for which class to use in computing the has code. Note that once any method to specify an attribute for a class is made, only the attributes specified (from that first call and any subsequent method calls) will be used for hashing.

Author:

James MacGlashan

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	DiscreteStateHashFactory.DiscreteStateHashTuple

Field Summary

Fields

Modifier and Type	Field and Description
protected java.util.Map<java.lang.String,java.util.List<Attribute>>	attributesForHashCode

Constructor Summary

Constructors

Constructor and Description
DiscreteStateHashFactory() Initializes this hashing factory to compute hash codes with all attributes of all object classes.
DiscreteStateHashFactory(java.util.Map<java.lang.String,java.util.List<Attribute>> attributesForHashCode) Initializes this hashing factory to hash on only the attributes for the specified classes in the provided map

Method Summary

Methods

Modifier and Type	Method and Description
void	addAttributeForClass(java.lang.String classname, Attribute att) Specifies that an additional attribute of the specified class should be used for computing hash codes.
StateHashTuple	hashState(State s)
void	setAttributesForClass(java.lang.String classname, java.util.List<Attribute> atts) Sets which attributes to use in the hash calculation for the given class.
void	setAttributesForHashCode(java.util.Map<java.lang.String,java.util.List<Attribute>> attributesForHashCode) Sets this hashing factory to hash on only the attributes for the specified classes in the provided map

Methods inherited from class java.lang.Object

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

Field Detail

attributesForHashCode

protected java.util.Map<java.lang.String,java.util.List<Attribute>> attributesForHashCode

Constructor Detail

DiscreteStateHashFactory

public DiscreteStateHashFactory()

Initializes this hashing factory to compute hash codes with all attributes of all object classes.

DiscreteStateHashFactory

public DiscreteStateHashFactory(java.util.Map<java.lang.String,java.util.List<Attribute>> attributesForHashCode)

Initializes this hashing factory to hash on only the attributes for the specified classes in the provided map

Parameters:

attributesForHashCode - a map from object class names to the attributes that should be used in the hash calculation for those object classes.

Method Detail

setAttributesForHashCode

public void setAttributesForHashCode(java.util.Map<java.lang.String,java.util.List<Attribute>> attributesForHashCode)

Sets this hashing factory to hash on only the attributes for the specified classes in the provided map

Parameters:

attributesForHashCode - a map from object class names to the attributes that should be used in the hash calculation for those object classes.

setAttributesForClass

public void setAttributesForClass(java.lang.String classname,
                         java.util.List<Attribute> atts)

Sets which attributes to use in the hash calculation for the given class. If this method has not be called before and the class was initialized with the default constructor, then only these class attributes, and those specified by subsequent calls to this method or those specified by a subsequent call of the other attribute setting methods will be used for computing hash codes

Parameters:

classname - the name of the class

atts - the attributes whose values in object instances should be used to compute hash codes

addAttributeForClass

public void addAttributeForClass(java.lang.String classname,
                        Attribute att)

Specifies that an additional attribute of the specified class should be used for computing hash codes. If this method has not be called before and the class was initialized with the default constructor, then only these class attributes, and those specified by subsequent calls to this method or those specified by a subsequent call of the other attribute setting methods will be used for computing hash codes

Parameters:

classname - the name of the class

att - the attribute whose values will be included in the computation of hash codes

hashState

public StateHashTuple hashState(State s)

Specified by:

hashState in interface StateHashFactory