org.apache.mahout.cf.taste.impl.recommender

Class CachingRecommender

java.lang.Object

org.apache.mahout.cf.taste.impl.recommender.CachingRecommender

All Implemented Interfaces:

Refreshable, Recommender

public final class CachingRecommender
extends Object
implements Recommender

A Recommender which caches the results from another Recommender in memory. TODO: Should be checked for thread safety

Constructor Summary

Constructors

Constructor and Description
CachingRecommender(Recommender recommender)

Method Summary

Modifier and Type	Method and Description
void	clear() Clears all cached recommendations.
void	clear(long userID) Clears cached recommendations for the given user.
float	estimatePreference(long userID, long itemID)
DataModel	getDataModel()
List<RecommendedItem>	recommend(long userID, int howMany)
List<RecommendedItem>	recommend(long userID, int howMany, boolean includeKnownItems)
List<RecommendedItem>	recommend(long userID, int howMany, IDRescorer rescorer)
List<RecommendedItem>	recommend(long userID, int howMany, IDRescorer rescorer, boolean includeKnownItems)
void	refresh(Collection<Refreshable> alreadyRefreshed) Triggers "refresh" -- whatever that means -- of the implementation.
void	removePreference(long userID, long itemID)
void	setCurrentlyIncludeKnownItems(boolean currentlyIncludeKnownItems)
void	setPreference(long userID, long itemID, float value)
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

CachingRecommender

public CachingRecommender(Recommender recommender)
                   throws TasteException

Throws:

TasteException

Method Detail

setCurrentlyIncludeKnownItems

public void setCurrentlyIncludeKnownItems(boolean currentlyIncludeKnownItems)

recommend

public List<RecommendedItem> recommend(long userID,
                                       int howMany)
                                throws TasteException

Specified by:

recommend in interface Recommender

Parameters:

userID - user for which recommendations are to be computed

howMany - desired number of recommendations

Returns:

List of recommended RecommendedItems, ordered from most strongly recommend to least

Throws:

TasteException - if an error occurs while accessing the DataModel

recommend

public List<RecommendedItem> recommend(long userID,
                                       int howMany,
                                       boolean includeKnownItems)
                                throws TasteException

Specified by:

recommend in interface Recommender

Parameters:

userID - user for which recommendations are to be computed

howMany - desired number of recommendations

includeKnownItems - whether to include items already known by the user in recommendations

Returns:

List of recommended RecommendedItems, ordered from most strongly recommend to least

Throws:

TasteException - if an error occurs while accessing the DataModel

recommend

public List<RecommendedItem> recommend(long userID,
                                       int howMany,
                                       IDRescorer rescorer)
                                throws TasteException

Specified by:

recommend in interface Recommender

Parameters:

userID - user for which recommendations are to be computed

howMany - desired number of recommendations

rescorer - rescoring function to apply before final list of recommendations is determined

Returns:

List of recommended RecommendedItems, ordered from most strongly recommend to least

Throws:

TasteException - if an error occurs while accessing the DataModel

recommend

public List<RecommendedItem> recommend(long userID,
                                       int howMany,
                                       IDRescorer rescorer,
                                       boolean includeKnownItems)
                                throws TasteException

Specified by:

recommend in interface Recommender

Parameters:

userID - user for which recommendations are to be computed

howMany - desired number of recommendations

rescorer - rescoring function to apply before final list of recommendations is determined

includeKnownItems - whether to include items already known by the user in recommendations

Returns:

List of recommended RecommendedItems, ordered from most strongly recommend to least

Throws:

TasteException - if an error occurs while accessing the DataModel

estimatePreference

public float estimatePreference(long userID,
                                long itemID)
                         throws TasteException

Specified by:

estimatePreference in interface Recommender

Parameters:

userID - user ID whose preference is to be estimated

itemID - item ID to estimate preference for

Returns:

an estimated preference if the user has not expressed a preference for the item, or else the user's actual preference for the item. If a preference cannot be estimated, returns Double.NaN

Throws:

TasteException - if an error occurs while accessing the DataModel

setPreference

public void setPreference(long userID,
                          long itemID,
                          float value)
                   throws TasteException

Specified by:

setPreference in interface Recommender

Parameters:

userID - user to set preference for

itemID - item to set preference for

value - preference value

Throws:

TasteException - if an error occurs while accessing the DataModel

removePreference

public void removePreference(long userID,
                             long itemID)
                      throws TasteException

Specified by:

removePreference in interface Recommender

Parameters:

userID - user from which to remove preference

itemID - item for which to remove preference

Throws:

TasteException - if an error occurs while accessing the DataModel

getDataModel

public DataModel getDataModel()

Specified by:

getDataModel in interface Recommender

Returns:

underlying DataModel used by this Recommender implementation

refresh

public void refresh(Collection<Refreshable> alreadyRefreshed)

Description copied from interface: Refreshable

Triggers "refresh" -- whatever that means -- of the implementation. The general contract is that any Refreshable should always leave itself in a consistent, operational state, and that the refresh atomically updates internal state from old to new.

Specified by:

refresh in interface Refreshable

Parameters:

alreadyRefreshed - Refreshables that are known to have already been refreshed as a result of an initial call to a {#refresh(Collection)} method on some object. This ensure that objects in a refresh dependency graph aren't refreshed twice needlessly.

clear

public void clear(long userID)

Clears cached recommendations for the given user.

Parameters:

userID - clear cached data associated with this user ID

clear

public void clear()

Clears all cached recommendations.

toString

public String toString()

Overrides:

toString in class Object