svd++

 

svd++

分类： 推荐系统 机器学习2013-05-31
20:50 836人阅读 评论(0) 收藏 举报

目录(?)[-]
CONTENTS
MODEL FORMALIZATION
GENERAL FORMALIZATION FOR USER FEEDBACK INFORMATION
LEARNING
LITERATURE
IMPLEMENTATIONS

SVD++ refers to a matrix factorization model which makes use of implicit
feedback information. In general, implicit feedback can refer to any kinds of users'
history information that can help indicate users' preference.

CONTENTS   [hide]  1 Model Formalization 2 General Formalization for User Feedback Information 3 Learning 4 Literature 5 Implementations

MODEL FORMALIZATION

The SVD++ model is formally described as following equation:



where 

 is the set of implicit information( the set of items user
u rated ).

GENERAL FORMALIZATION FOR USER FEEDBACK INFORMATION

A more general form of utilizing implicit/explicit information as user factor can be described in following equation



Here 

 is the set of user feedback information( e.g: the web pages
the user clicked, the music on users' favorite list, the movies user watched, any kinds of information that can be used to describe the user). 

 is
a feature weightassociates with the user feedback information. With the most two common choices: (1) 

 for
implicit feedback, (2) 

 for explicit
feedback.

（一直搞不清楚上面公式当中yi到底是什么，现在清楚了，yi就是上面所写出来的隐式反馈！）

LEARNING

SVD++ can be trained using ALS.

It is slow to train a SVD++-style model using stochastic
gradient descent due to the size of user feedback information, however, an efficient SGD training algorithm can be used. [1] describes
efficient training with user feedback information in section 4

LITERATURE

Yehuda
Koren: Factorization meets the neighborhood: a multifaceted collaborative filtering model, KDD 2008, http://portal.acm.org/citation.cfm?id=1401890.1401944

IMPLEMENTATIONS

The GraphLab Collaborative
Filtering Library has implemented SVD++ for multicore: http://graphlab.org/pmf.html
SVDFeature is a toolkit designed for feature-based matrix factorization,
can be used to implement SVD++ and its extensions.
LibFM can
also be used to implement SVD++
wooflix is
a (not very fast) Python implementation
of SVD++
MyMediaLite: SVD++
source code on GitHub; see also [2]