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

Class AbstractRecommender

java.lang.Object

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

All Implemented Interfaces:

Refreshable, Recommender

Direct Known Subclasses:

GenericItemBasedRecommender, GenericUserBasedRecommender, ItemAverageRecommender, ItemUserAverageRecommender, RandomRecommender, SVDRecommender

public abstract class AbstractRecommender
extends Object
implements Recommender

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractRecommender(DataModel dataModel)
protected	AbstractRecommender(DataModel dataModel, CandidateItemsStrategy candidateItemsStrategy)

Method Summary

Modifier and Type	Method and Description
protected FastIDSet	getAllOtherItems(long userID, PreferenceArray preferencesFromUser, boolean includeKnownItems)
DataModel	getDataModel()
protected static CandidateItemsStrategy	getDefaultCandidateItemsStrategy()
List<RecommendedItem>	recommend(long userID, int howMany) Default implementation which just calls Recommender.recommend(long, int, org.apache.mahout.cf.taste.recommender.IDRescorer), with a Rescorer that does nothing.
List<RecommendedItem>	recommend(long userID, int howMany, boolean includeKnownItems) Default implementation which just calls Recommender.recommend(long, int, org.apache.mahout.cf.taste.recommender.IDRescorer), with a Rescorer that does nothing.
List<RecommendedItem>	recommend(long userID, int howMany, IDRescorer rescorer) Delegates to Recommender.recommend(long, int, IDRescorer, boolean)
void	removePreference(long userID, long itemID) Default implementation which just calls DataModel.removePreference(long, long) (Object, Object)}.
void	setPreference(long userID, long itemID, float value) Default implementation which just calls DataModel.setPreference(long, long, float).

Methods inherited from class java.lang.Object

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

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

estimatePreference, recommend

Methods inherited from interface org.apache.mahout.cf.taste.common.Refreshable

refresh

Constructor Detail

AbstractRecommender

protected AbstractRecommender(DataModel dataModel,
                              CandidateItemsStrategy candidateItemsStrategy)

AbstractRecommender

protected AbstractRecommender(DataModel dataModel)

Method Detail

getDefaultCandidateItemsStrategy

protected static CandidateItemsStrategy getDefaultCandidateItemsStrategy()

recommend

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

Default implementation which just calls Recommender.recommend(long, int, org.apache.mahout.cf.taste.recommender.IDRescorer), with a Rescorer that does nothing.

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

Default implementation which just calls Recommender.recommend(long, int, org.apache.mahout.cf.taste.recommender.IDRescorer), with a Rescorer that does nothing.

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

Delegates to Recommender.recommend(long, int, IDRescorer, boolean)

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

setPreference

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

Default implementation which just calls DataModel.setPreference(long, long, float).

Specified by:

setPreference in interface Recommender

Parameters:

userID - user to set preference for

itemID - item to set preference for

value - preference value

Throws:

IllegalArgumentException - if userID or itemID is null, or if value is Double.NaN

TasteException - if an error occurs while accessing the DataModel

removePreference

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

Default implementation which just calls DataModel.removePreference(long, long) (Object, Object)}.

Specified by:

removePreference in interface Recommender

Parameters:

userID - user from which to remove preference

itemID - item for which to remove preference

Throws:

IllegalArgumentException - if userID or itemID is null

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

getAllOtherItems

protected FastIDSet getAllOtherItems(long userID,
                                     PreferenceArray preferencesFromUser,
                                     boolean includeKnownItems)
                              throws TasteException

Parameters:

userID - ID of user being evaluated

preferencesFromUser - the preferences from the user

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

Returns:

all items in the DataModel for which the user has not expressed a preference and could possibly be recommended to the user

Throws:

TasteException - if an error occurs while listing items