org.apache.mahout.cf.taste.impl.model

Class PlusAnonymousConcurrentUserDataModel

java.lang.Object

org.apache.mahout.cf.taste.impl.model.PlusAnonymousUserDataModel

org.apache.mahout.cf.taste.impl.model.PlusAnonymousConcurrentUserDataModel

All Implemented Interfaces:

Serializable, Refreshable, DataModel

public final class PlusAnonymousConcurrentUserDataModel
extends PlusAnonymousUserDataModel

This is a special thread-safe version of PlusAnonymousUserDataModel which allow multiple concurrent anonymous requests.

To use it, you have to estimate the number of concurrent anonymous users of your application. The pool of users with the given size will be created. For each anonymous recommendations request, a user has to be taken from the pool and returned back immediately afterwards.

If no more users are available in the pool, anonymous recommendations cannot be produced.

Setup:

 int concurrentUsers = 100;
 DataModel realModel = ..
 PlusAnonymousConcurrentUserDataModel plusModel =
   new PlusAnonymousConcurrentUserDataModel(realModel, concurrentUsers);
 Recommender recommender = ...;
 

Real-time recommendation:

 PlusAnonymousConcurrentUserDataModel plusModel =
   (PlusAnonymousConcurrentUserDataModel) recommender.getDataModel();

 // Take the next available anonymous user from the pool
 Long anonymousUserID = plusModel.takeAvailableUser();

 PreferenceArray tempPrefs = ..
 tempPrefs.setUserID(0, anonymousUserID);
 tempPrefs.setItemID(0, itemID);
 plusModel.setTempPrefs(tempPrefs, anonymousUserID);

 // Produce recommendations
 recommender.recommend(anonymousUserID, howMany);

 // It is very IMPORTANT to release user back to the pool
 plusModel.releaseUser(anonymousUserID);
 

See Also:

Serialized Form

Field Summary

Fields inherited from class org.apache.mahout.cf.taste.impl.model.PlusAnonymousUserDataModel

TEMP_USER_ID

Constructor Summary

Constructors

Constructor and Description
PlusAnonymousConcurrentUserDataModel(DataModel delegate, int maxConcurrentUsers)

Method Summary

Modifier and Type	Method and Description
void	clearTempPrefs(long anonymousUserID) Clears temporary preferences for a given anonymous user.
FastIDSet	getItemIDsFromUser(long userID)
int	getNumUsers()
int	getNumUsersWithPreferenceFor(long itemID)
int	getNumUsersWithPreferenceFor(long itemID1, long itemID2)
PreferenceArray	getPreferencesForItem(long itemID)
PreferenceArray	getPreferencesFromUser(long userID)
Long	getPreferenceTime(long userID, long itemID) Retrieves the time at which a preference value from a user and item was set, if known.
Float	getPreferenceValue(long userID, long itemID) Retrieves the preference value for a single user and item.
LongPrimitiveIterator	getUserIDs()
boolean	releaseUser(Long userID) Release previously taken anonymous user and return it to the pool.
void	removePreference(long userID, long itemID) Removes a particular preference for a user.
void	setPreference(long userID, long itemID, float value) Sets a particular preference (item plus rating) for a user.
void	setTempPrefs(PreferenceArray prefs, long anonymousUserID) Sets temporary preferences for a given anonymous user.
Long	takeAvailableUser() Take the next available concurrent anonymous users from the pool.

Methods inherited from class org.apache.mahout.cf.taste.impl.model.PlusAnonymousUserDataModel

clearTempPrefs, getDelegate, getItemIDs, getMaxPreference, getMinPreference, getNumItems, hasPreferenceValues, refresh, setTempPrefs

Methods inherited from class java.lang.Object

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

Constructor Detail

PlusAnonymousConcurrentUserDataModel

public PlusAnonymousConcurrentUserDataModel(DataModel delegate,
                                            int maxConcurrentUsers)

Parameters:

delegate - Real model where anonymous users will be added to

maxConcurrentUsers - Maximum allowed number of concurrent anonymous users

Method Detail

takeAvailableUser

public Long takeAvailableUser()

Take the next available concurrent anonymous users from the pool.

Returns:

User ID or null if no more users are available

releaseUser

public boolean releaseUser(Long userID)

Release previously taken anonymous user and return it to the pool.

Parameters:

userID - ID of a previously taken anonymous user

Returns:

true if the user was previously taken, false otherwise

setTempPrefs

public void setTempPrefs(PreferenceArray prefs,
                         long anonymousUserID)

Sets temporary preferences for a given anonymous user.

clearTempPrefs

public void clearTempPrefs(long anonymousUserID)

Clears temporary preferences for a given anonymous user.

getUserIDs

public LongPrimitiveIterator getUserIDs()
                                 throws TasteException

Specified by:

getUserIDs in interface DataModel

Overrides:

getUserIDs in class PlusAnonymousUserDataModel

Returns:

all user IDs in the model, in order

Throws:

TasteException - if an error occurs while accessing the data

getPreferencesFromUser

public PreferenceArray getPreferencesFromUser(long userID)
                                       throws TasteException

Specified by:

getPreferencesFromUser in interface DataModel

Overrides:

getPreferencesFromUser in class PlusAnonymousUserDataModel

Parameters:

userID - ID of user to get prefs for

Returns:

user's preferences, ordered by item ID

Throws:

NoSuchUserException - if the user does not exist

TasteException - if an error occurs while accessing the data

getItemIDsFromUser

public FastIDSet getItemIDsFromUser(long userID)
                             throws TasteException

Specified by:

getItemIDsFromUser in interface DataModel

Overrides:

getItemIDsFromUser in class PlusAnonymousUserDataModel

Parameters:

userID - ID of user to get prefs for

Returns:

IDs of items user expresses a preference for

Throws:

NoSuchUserException - if the user does not exist

TasteException - if an error occurs while accessing the data

getPreferencesForItem

public PreferenceArray getPreferencesForItem(long itemID)
                                      throws TasteException

Specified by:

getPreferencesForItem in interface DataModel

Overrides:

getPreferencesForItem in class PlusAnonymousUserDataModel

Parameters:

itemID - item ID

Returns:

all existing Preferences expressed for that item, ordered by user ID, as an array

Throws:

NoSuchItemException - if the item does not exist

TasteException - if an error occurs while accessing the data

getPreferenceValue

public Float getPreferenceValue(long userID,
                                long itemID)
                         throws TasteException

Description copied from interface: DataModel

Retrieves the preference value for a single user and item.

Specified by:

getPreferenceValue in interface DataModel

Overrides:

getPreferenceValue in class PlusAnonymousUserDataModel

Parameters:

userID - user ID to get pref value from

itemID - item ID to get pref value for

Returns:

preference value from the given user for the given item or null if none exists

Throws:

NoSuchUserException - if the user does not exist

TasteException - if an error occurs while accessing the data

getPreferenceTime

public Long getPreferenceTime(long userID,
                              long itemID)
                       throws TasteException

Description copied from interface: DataModel

Retrieves the time at which a preference value from a user and item was set, if known. Time is expressed in the usual way, as a number of milliseconds since the epoch.

Specified by:

getPreferenceTime in interface DataModel

Overrides:

getPreferenceTime in class PlusAnonymousUserDataModel

Parameters:

userID - user ID for preference in question

itemID - item ID for preference in question

Returns:

time at which preference was set or null if no preference exists or its time is not known

Throws:

NoSuchUserException - if the user does not exist

TasteException - if an error occurs while accessing the data

getNumUsers

public int getNumUsers()
                throws TasteException

Specified by:

getNumUsers in interface DataModel

Overrides:

getNumUsers in class PlusAnonymousUserDataModel

Returns:

total number of users known to the model.

Throws:

TasteException - if an error occurs while accessing the data

getNumUsersWithPreferenceFor

public int getNumUsersWithPreferenceFor(long itemID)
                                 throws TasteException

Specified by:

getNumUsersWithPreferenceFor in interface DataModel

Overrides:

getNumUsersWithPreferenceFor in class PlusAnonymousUserDataModel

Parameters:

itemID - item ID to check for

Returns:

the number of users who have expressed a preference for the item

Throws:

TasteException - if an error occurs while accessing the data

getNumUsersWithPreferenceFor

public int getNumUsersWithPreferenceFor(long itemID1,
                                        long itemID2)
                                 throws TasteException

Specified by:

getNumUsersWithPreferenceFor in interface DataModel

Overrides:

getNumUsersWithPreferenceFor in class PlusAnonymousUserDataModel

Parameters:

itemID1 - first item ID to check for

itemID2 - second item ID to check for

Returns:

the number of users who have expressed a preference for the items

Throws:

TasteException - if an error occurs while accessing the data

setPreference

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

Description copied from interface: DataModel

Sets a particular preference (item plus rating) for a user.

Specified by:

setPreference in interface DataModel

Overrides:

setPreference in class PlusAnonymousUserDataModel

Parameters:

userID - user to set preference for

itemID - item to set preference for

value - preference value

Throws:

NoSuchItemException - if the item does not exist

NoSuchUserException - if the user does not exist

TasteException - if an error occurs while accessing the data

removePreference

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

Description copied from interface: DataModel

Removes a particular preference for a user.

Specified by:

removePreference in interface DataModel

Overrides:

removePreference in class PlusAnonymousUserDataModel

Parameters:

userID - user from which to remove preference

itemID - item to remove preference for

Throws:

NoSuchItemException - if the item does not exist

NoSuchUserException - if the user does not exist

TasteException - if an error occurs while accessing the data