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

Class GenericUserBasedRecommender

java.lang.Object

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

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

All Implemented Interfaces:

Refreshable, Recommender, UserBasedRecommender

Direct Known Subclasses:

GenericBooleanPrefUserBasedRecommender

public class GenericUserBasedRecommender
extends AbstractRecommender
implements UserBasedRecommender

A simple Recommender which uses a given DataModel and UserNeighborhood to produce recommendations.

Constructor Summary

Constructors

Constructor and Description
GenericUserBasedRecommender(DataModel dataModel, UserNeighborhood neighborhood, UserSimilarity similarity)

Method Summary

Modifier and Type	Method and Description
protected float	doEstimatePreference(long theUserID, long[] theNeighborhood, long itemID)
float	estimatePreference(long userID, long itemID)
protected FastIDSet	getAllOtherItems(long[] theNeighborhood, long theUserID, boolean includeKnownItems)
UserSimilarity	getSimilarity()
long[]	mostSimilarUserIDs(long userID, int howMany)
long[]	mostSimilarUserIDs(long userID, int howMany, Rescorer<LongPair> 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.
String	toString()

Methods inherited from class org.apache.mahout.cf.taste.impl.recommender.AbstractRecommender

getAllOtherItems, getDataModel, getDefaultCandidateItemsStrategy, recommend, recommend, recommend, removePreference, setPreference

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.mahout.cf.taste.recommender.Recommender

getDataModel, recommend, recommend, recommend, removePreference, setPreference

Constructor Detail

GenericUserBasedRecommender

public GenericUserBasedRecommender(DataModel dataModel,
                                   UserNeighborhood neighborhood,
                                   UserSimilarity similarity)

Method Detail

getSimilarity

public UserSimilarity getSimilarity()

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

mostSimilarUserIDs

public long[] mostSimilarUserIDs(long userID,
                                 int howMany)
                          throws TasteException

Specified by:

mostSimilarUserIDs in interface UserBasedRecommender

Parameters:

userID - ID of user for which to find most similar other users

howMany - desired number of most similar users to find

Returns:

users most similar to the given user

Throws:

TasteException - if an error occurs while accessing the DataModel

mostSimilarUserIDs

public long[] mostSimilarUserIDs(long userID,
                                 int howMany,
                                 Rescorer<LongPair> rescorer)
                          throws TasteException

Specified by:

mostSimilarUserIDs in interface UserBasedRecommender

Parameters:

userID - ID of user for which to find most similar other users

howMany - desired number of most similar users to find

rescorer - Rescorer which can adjust user-user similarity estimates used to determine most similar users

Returns:

IDs of users most similar to the given user

Throws:

TasteException - if an error occurs while accessing the DataModel

doEstimatePreference

protected float doEstimatePreference(long theUserID,
                                     long[] theNeighborhood,
                                     long itemID)
                              throws TasteException

Throws:

TasteException

getAllOtherItems

protected FastIDSet getAllOtherItems(long[] theNeighborhood,
                                     long theUserID,
                                     boolean includeKnownItems)
                              throws TasteException

Throws:

TasteException

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.

toString

public String toString()

Overrides:

toString in class Object