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SVDPlusPlus Class Reference

SVD++: Matrix factorization that also takes into account what users have rated More...

Inheritance diagram for SVDPlusPlus:
MatrixFactorization ITransductiveRatingPredictor IncrementalRatingPredictor IIterativeModel IFoldInRatingPredictor IRatingPredictor RatingPredictor IIncrementalRatingPredictor IRatingPredictor IRecommender Recommender IRatingPredictor IRatingPredictor IIncrementalRecommender IRecommender IRecommender IRecommender IRecommender GSVDPlusPlus SigmoidSVDPlusPlus

Public Member Functions

override void AddRatings (IRatings ratings)
 Add new ratings and perform incremental training
virtual bool CanPredict (int user_id, int item_id)
 Check whether a useful prediction (i.e. not using a fallback/default answer) can be made for a given user-item combination
Object Clone ()
 create a shallow copy of the object
override float ComputeObjective ()
 Compute the regularized loss
virtual void Iterate ()
 Run one iteration (= pass over the training data)
override void LoadModel (string filename)
 Get the model parameters from a file
override float Predict (int user_id, int item_id)
 Predict the rating of a given user for a given item
IList< Tuple< int, float > > Recommend (int user_id, int n=-1, ICollection< int > ignore_items=null, ICollection< int > candidate_items=null)
 Recommend items for a given user
virtual
System.Collections.Generic.IList
< Tuple< int, float > > 
Recommend (int user_id, int n=-1, System.Collections.Generic.ICollection< int > ignore_items=null, System.Collections.Generic.ICollection< int > candidate_items=null)
override void RemoveItem (int item_id)
 Remove all feedback by one item
override void RemoveRatings (IDataSet ratings)
 Remove existing ratings and perform "incremental" training
override void RemoveUser (int user_id)
 Remove all feedback by one user
virtual void RetrainItem (int item_id)
 Updates the latent factors of an item
override void RetrainUser (int user_id)
 Updates the latent factors on a user
override void SaveModel (string filename)
 Save the model parameters to a file
IList< Tuple< int, float > > ScoreItems (IList< Tuple< int, float >> rated_items, IList< int > candidate_items)
 Rate a list of items given a list of ratings that represent a new user
 SVDPlusPlus ()
 Default constructor
override string ToString ()
 Return a string representation of the recommender
override void Train ()
 Learn the model parameters of the recommender from the training data
override void UpdateRatings (IRatings ratings)
 Update existing ratings and perform incremental training

Protected Member Functions

override void AddItem (int item_id)
override void AddUser (int user_id)
virtual double ComputeLoss ()
 Compute the value of the loss function that is currently being optimized (RMSE)
override float[] FoldIn (IList< Tuple< int, float >> rated_items)
 Compute parameters (latent factors) for a user represented by ratings
override void Iterate (IList< int > rating_indices, bool update_user, bool update_item)
 Iterate once over rating data and adjust corresponding factors (stochastic gradient descent)
void PrecomputeFactors (int user_id)
 Precompute the factors for a given user
void PrecomputeUserFactors ()
 Precompute all user factors
float Predict (int user_id, int item_id, bool bound)
override float Predict (float[] user_vector, int item_id)
 Predict rating for a fold-in user and an item
virtual void UpdateLearnRate ()
 Updates current_learnrate after each epoch

Protected Attributes

float global_bias
 The bias (global average)
int[][] items_rated_by_user
 The items rated by the users
float max_rating
 Maximum rating value
float min_rating
 Minimum rating value
IRatings ratings
 rating data
float[] y_reg
 precomputed regularization terms for the y matrix

Properties

IDataSet AdditionalFeedback [get, set]
float BiasLearnRate [get, set]
 bias learn rate
float BiasReg [get, set]
 regularization constant for biases
float Decay [get, set]
 Multiplicative learn rate decay
bool FrequencyRegularization [get, set]
 Regularization based on rating frequency
double InitMean [get, set]
 Mean of the normal distribution used to initialize the factors
double InitStdDev [get, set]
 Standard deviation of the normal distribution used to initialize the factors
float LearnRate [get, set]
 Learn rate (update step size)
int MaxItemID [get, set]
 Maximum item ID
virtual float MaxRating [get, set]
 Maximum rating value
int MaxUserID [get, set]
 Maximum user ID
virtual float MinRating [get, set]
 Minimum rating value
uint NumFactors [get, set]
 Number of latent factors
uint NumIter [get, set]
 Number of iterations over the training data
virtual IRatings Ratings [get, set]
 The rating data
virtual float Regularization [get, set]
 Regularization parameter
bool UpdateItems [get, set]
bool UpdateUsers [get, set]

Detailed Description

SVD++: Matrix factorization that also takes into account what users have rated

Literature:

Constructor & Destructor Documentation

SVDPlusPlus ( )
inline

Default constructor

Member Function Documentation

override void AddRatings ( IRatings  ratings)
inlinevirtualinherited

Add new ratings and perform incremental training

Parameters
ratingsthe ratings

Reimplemented from IncrementalRatingPredictor.

virtual bool CanPredict ( int  user_id,
int  item_id 
)
inlinevirtualinherited

Check whether a useful prediction (i.e. not using a fallback/default answer) can be made for a given user-item combination

It is up to the recommender implementor to decide when a prediction is useful, and to document it accordingly.

Parameters
user_idthe user ID
item_idthe item ID
Returns
true if a useful prediction can be made, false otherwise

Implements IRecommender.

Reimplemented in ExternalItemRecommender, ExternalRatingPredictor, BiPolarSlopeOne, SlopeOne, Constant, GlobalAverage, UserAverage, ItemAverage, and Random.

Object Clone ( )
inlineinherited

create a shallow copy of the object

virtual double ComputeLoss ( )
inlineprotectedvirtual

Compute the value of the loss function that is currently being optimized (RMSE)

Returns
the loss

Reimplemented in SigmoidSVDPlusPlus.

override float ComputeObjective ( )
inlinevirtual

Compute the regularized loss

Returns
the regularized loss

Reimplemented from MatrixFactorization.

override float [] FoldIn ( IList< Tuple< int, float >>  rated_items)
inlineprotectedvirtual

Compute parameters (latent factors) for a user represented by ratings

Returns
a vector of latent factors
Parameters
rated_itemsa list of (item ID, rating value) pairs

Reimplemented from MatrixFactorization.

Reimplemented in GSVDPlusPlus, and SigmoidSVDPlusPlus.

virtual void Iterate ( )
inlinevirtualinherited

Run one iteration (= pass over the training data)

Implements IIterativeModel.

Reimplemented in BiasedMatrixFactorization.

override void Iterate ( IList< int >  rating_indices,
bool  update_user,
bool  update_item 
)
inlineprotectedvirtual

Iterate once over rating data and adjust corresponding factors (stochastic gradient descent)

Parameters
rating_indicesa list of indices pointing to the ratings to iterate over
update_usertrue if user factors to be updated
update_itemtrue if item factors to be updated

Reimplemented from MatrixFactorization.

Reimplemented in SigmoidSVDPlusPlus, and GSVDPlusPlus.

override void LoadModel ( string  filename)
inline

Get the model parameters from a file

Parameters
filenamethe name of the file to read from

Reimplemented from MatrixFactorization.

Reimplemented in SigmoidSVDPlusPlus.

void PrecomputeFactors ( int  user_id)
inlineprotected

Precompute the factors for a given user

Parameters
user_idthe ID of the user
void PrecomputeUserFactors ( )
inlineprotected

Precompute all user factors

override float Predict ( int  user_id,
int  item_id 
)
inline

Predict the rating of a given user for a given item

If the user or the item are not known to the recommender, the global average is returned. To avoid this behavior for unknown entities, use CanPredict() to check before.

Parameters
user_idthe user ID
item_idthe item ID
Returns
the predicted rating

Reimplemented from MatrixFactorization.

Reimplemented in GSVDPlusPlus, and SigmoidSVDPlusPlus.

override float Predict ( float[]  user_vector,
int  item_id 
)
inlineprotectedvirtual

Predict rating for a fold-in user and an item

Parameters
user_vectora float vector representing the user
item_idthe item ID
Returns
the predicted rating

Reimplemented from MatrixFactorization.

IList<Tuple<int, float> > Recommend ( int  user_id,
int  n = -1,
ICollection< int >  ignore_items = null,
ICollection< int >  candidate_items = null 
)
inherited

Recommend items for a given user

Parameters
user_idthe user ID
nthe number of items to recommend, -1 for as many as possible
ignore_itemscollection if items that should not be returned; if null, use empty collection
candidate_itemsthe candidate items to choose from; if null, use all items
Returns
a sorted list of (item_id, score) tuples

Implemented in WeightedEnsemble, and Ensemble.

override void RemoveItem ( int  item_id)
inlinevirtualinherited

Remove all feedback by one item

Parameters
item_idthe item ID

Reimplemented from IncrementalRatingPredictor.

Reimplemented in BiasedMatrixFactorization.

override void RemoveRatings ( IDataSet  ratings)
inlinevirtualinherited

Remove existing ratings and perform "incremental" training

Parameters
ratingsthe user and item IDs of the ratings to be removed

Reimplemented from IncrementalRatingPredictor.

override void RemoveUser ( int  user_id)
inlinevirtualinherited

Remove all feedback by one user

Parameters
user_idthe user ID

Reimplemented from IncrementalRatingPredictor.

Reimplemented in BiasedMatrixFactorization.

virtual void RetrainItem ( int  item_id)
inlinevirtualinherited

Updates the latent factors of an item

Parameters
item_idthe item ID

Reimplemented in BiasedMatrixFactorization.

override void RetrainUser ( int  user_id)
inlinevirtual

Updates the latent factors on a user

Parameters
user_idthe user ID

Reimplemented from MatrixFactorization.

override void SaveModel ( string  filename)
inline

Save the model parameters to a file

Parameters
filenamethe name of the file to write to

Reimplemented from MatrixFactorization.

IList<Tuple<int, float> > ScoreItems ( IList< Tuple< int, float >>  rated_items,
IList< int >  candidate_items 
)
inlineinherited

Rate a list of items given a list of ratings that represent a new user

Returns
a list of int and float pairs, representing item IDs and predicted ratings
Parameters
rated_itemsthe ratings (item IDs and rating values) representing the new user
candidate_itemsthe items to be rated

Implements IFoldInRatingPredictor.

override string ToString ( )
inline

Return a string representation of the recommender

The ToString() method of recommenders should list the class name and all hyperparameters, separated by space characters.

Reimplemented from MatrixFactorization.

Reimplemented in SigmoidSVDPlusPlus.

override void Train ( )
inline

Learn the model parameters of the recommender from the training data

Reimplemented from MatrixFactorization.

Reimplemented in GSVDPlusPlus, and SigmoidSVDPlusPlus.

virtual void UpdateLearnRate ( )
inlineprotectedvirtualinherited

Updates current_learnrate after each epoch

Reimplemented in BiasedMatrixFactorization.

override void UpdateRatings ( IRatings  ratings)
inlinevirtualinherited

Update existing ratings and perform incremental training

Parameters
ratingsthe ratings

Reimplemented from IncrementalRatingPredictor.

Member Data Documentation

float global_bias
protectedinherited

The bias (global average)

int [][] items_rated_by_user
protected

The items rated by the users

float max_rating
protectedinherited

Maximum rating value

float min_rating
protectedinherited

Minimum rating value

IRatings ratings
protectedinherited

rating data

float [] y_reg
protected

precomputed regularization terms for the y matrix

Property Documentation

float BiasLearnRate
getset

bias learn rate

float BiasReg
getset

regularization constant for biases

float Decay
getsetinherited

Multiplicative learn rate decay

Applied after each epoch (= pass over the whole dataset)

bool FrequencyRegularization
getset

Regularization based on rating frequency

Regularization proportional to the inverse of the square root of the number of ratings associated with the user or item. As described in the paper by Menon and Elkan.

double InitMean
getsetinherited

Mean of the normal distribution used to initialize the factors

double InitStdDev
getsetinherited

Standard deviation of the normal distribution used to initialize the factors

float LearnRate
getsetinherited

Learn rate (update step size)

int MaxItemID
getsetinherited

Maximum item ID

virtual float MaxRating
getsetinherited

Maximum rating value

int MaxUserID
getsetinherited

Maximum user ID

virtual float MinRating
getsetinherited

Minimum rating value

uint NumFactors
getsetinherited

Number of latent factors

uint NumIter
getsetinherited

Number of iterations over the training data

virtual IRatings Ratings
getsetinherited

The rating data

virtual float Regularization
getsetinherited

Regularization parameter


The documentation for this class was generated from the following file: