6. hort-term and long-term preferences. Stra
それを踏まえて式を見ていく
described as:
Pr ( sb |sa , u) ∝
次に選ぶ曲
− x( sa )−x( sb )
e
2
−
2
曲同士
y(u)−x( sb )
2
2
曲とユーザ 2
− x( sa )−x( sb ) 2
Pr ( sb |sa ) is proportional to e
er information is ignored by LME, while b
• 学習するのはxとy
PME. R^d次元の曲/曲空間と曲/ユーザ空間を考えたい
•
•
•
x: 曲をR^d次元の空間に写像する関数
y: 曲をR^d次元の空間に写像する関数
8. 1
2
|U|
Then, we could transform Equation (3) into its equivalent form
学習: 最尤推定
by applying the ln function:
(X, Y) = arg max
X,Y
| pu | | pu, j |
(u,pu )∈D j=1 k=2
= arg max
X,Y
u∈U sa ∈S sb ∈S
= arg max
X,Y
u∈U sa ∈S sb ∈S
− y (u) − x (sb )
def
2
2
(k−1)
pu, j , u
cu,sa ,sb ln Pr (sb |sa , u )
cu,sa ,sb − x (sa ) − x (sb )
− ln
= arg max L1 (D |X, Y )
X,Y
ln Pr
(k)
pu, j
s∈S
2
2
(4)
2 − y(u)−x(s) 2
− x(sa )−x(s) 2
2
e
where cu,sa ,sb is the number of occurrence of song sb after song sa by
9. 学習: 最尤推定
(X, Y) = arg max
X,Y
| pu | | pu, j |
(u,pu )∈D j=1 k=2
= arg max
X,Y
ln Pr
u∈U sa ∈S sb ∈S
(k)
pu, j
(k−1)
pu, j , u
cu,sa ,sb ln Pr (sb |sa , u )
cu,sa ,sb − x (sa ) − x (sb )
!!!max
O(¦U¦ * ¦S¦^2) !!!
= arg
X,Y
u∈U sa ∈S sb ∈S
− y (u) − x (sb )
def
2
2
− ln
= arg max L1 (D |X, Y )
X,Y
s∈S
2
2
2 − y(u)−x(s) 2
− x(sa )−x(s) 2
2
e
10. n, to overcome the time-consuming problem, we propo
学習
n (5) to simulate Equation (2). In this way, the two ty
ean distances can be decoupled:
Pr (sb |sa ) Pr (sb |u) =
− x( sa )−x( sb )
e
s∈S
2
2
− x(sa )−x(s) 2
2
e
− y(u)−x( sb )
e
2
2
− y(u)−x(s) 2
2
s∈S e
Pr ( sb |sa ) is the transition probability from song sa to so
( sb |u) is the probability of user u singing song sb . Not
on (5) is not simply an assembled model, since all param
• 重すぎるので,曲/曲と曲/ユーザの項を分解
e trained simultaneously.
これでO(¦U¦ * ¦S¦)
• a similar process of Equation (3) and Equation (4
owing あとは正則化して勾配法で最急降下法で学習
•
get:
(X, Y) = arg max
cu,sa ,sb ln Pr (sb |sa ) Pr (sb |u)
12. transitions have comparably low occurrence rate, PME could outperforms LME and Bigram in real applications, i.e., PME is better
at predicting the unseen and sparse data.
Embedding例
5
Songs
Songs of User 1
Songs of User 2
Songs of User 3
4
[4]
[5]
[6]
3
[7]
2
User 2
1
User 1
-4
-3
-2
[8]
0
-1
0
1
2
3
4
5
-1
User 3
[9]
-2
-3
[10]
-4
Figure 4: Visualization of PME in R2 .
Case Study. Figure 4 is a visualization of the trained PME model
in R2 where all songs are represented by blue dots and 3 randomly
picked users are represented by circles with different colors. We
[11]
[12]
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