È äðóãèå êàòåãîðèè
I Çàâåäåíèÿ íà êàðòå
I Íîâîñòè, ñòàòüè, ñàéòû
I Êîíöåðòû, òåàòðû, âûñòàâêè
I Âèäåî
I Êíèãè
I Ïðèëîæåíèÿ
I Èãðû
I Ïóòåøåñòâèÿ
I Ñîöèàëüíûå ñâÿçè
I . . .
7
11.
Âèäû ðåêîìåíäàòåëüíûõ ñèñòåì
I Content-based
I Ïîëüçîâàòåëþ ðåêîìåíäóþòñÿ îáúåêòû, ïîõîæèå íà òå,
êîòîðûå ýòîò ïîëüçîâàòåëü óæå óïîòðåáèë.
I Ïîõîæåñòè îöåíèâàþòñÿ ïî ïðèçíàêàì ñîäåðæèìîãî
îáúåêòîâ.
I Ñèëüíàÿ çàâèñèìîñòü îò ïðåäìåòíîé îáëàñòè, ïîëåçíîñòü
ðåêîìåíäàöèé îãðàíè÷åíà.
8
12.
Âèäû ðåêîìåíäàòåëüíûõ ñèñòåì
I Content-based
I Ïîëüçîâàòåëþ ðåêîìåíäóþòñÿ îáúåêòû, ïîõîæèå íà òå,
êîòîðûå ýòîò ïîëüçîâàòåëü óæå óïîòðåáèë.
I Ïîõîæåñòè îöåíèâàþòñÿ ïî ïðèçíàêàì ñîäåðæèìîãî
îáúåêòîâ.
I Ñèëüíàÿ çàâèñèìîñòü îò ïðåäìåòíîé îáëàñòè, ïîëåçíîñòü
ðåêîìåíäàöèé îãðàíè÷åíà.
I Êîëëàáîðàòèâíàÿ ôèëüòðàöèÿ (Collaborative Filtering)
I Äëÿ ðåêîìåíäàöèé èñïîëüçóåòñÿ èñòîðèÿ îöåíîê êàê
ñàìîãî ïîëüçîâàòåëÿ, òàê è äðóãèõ ïîëüçîâàòåëåé.
I Áîëåå óíèâåðñàëüíûé ïîäõîä, ÷àñòî äàåò ëó÷øèé ðåçóëüòàò.
I Åñòü ñâîè ïðîáëåìû (íàïðèìåð, õîëîäíûé ñòàðò).
8
13.
Âèäû ðåêîìåíäàòåëüíûõ ñèñòåì
I Content-based
I Ïîëüçîâàòåëþ ðåêîìåíäóþòñÿ îáúåêòû, ïîõîæèå íà òå,
êîòîðûå ýòîò ïîëüçîâàòåëü óæå óïîòðåáèë.
I Ïîõîæåñòè îöåíèâàþòñÿ ïî ïðèçíàêàì ñîäåðæèìîãî
îáúåêòîâ.
I Ñèëüíàÿ çàâèñèìîñòü îò ïðåäìåòíîé îáëàñòè, ïîëåçíîñòü
ðåêîìåíäàöèé îãðàíè÷åíà.
I Êîëëàáîðàòèâíàÿ ôèëüòðàöèÿ (Collaborative Filtering)
I Äëÿ ðåêîìåíäàöèé èñïîëüçóåòñÿ èñòîðèÿ îöåíîê êàê
ñàìîãî ïîëüçîâàòåëÿ, òàê è äðóãèõ ïîëüçîâàòåëåé.
I Áîëåå óíèâåðñàëüíûé ïîäõîä, ÷àñòî äàåò ëó÷øèé ðåçóëüòàò.
I Åñòü ñâîè ïðîáëåìû (íàïðèìåð, õîëîäíûé ñòàðò).
I Ãèáðèäíûå ñèñòåìû
I Ñî÷åòàþò îáà ïîäõîäà.
8
14.
Netflix Prize
Ðàññâåòðåêîìåíäàòåëüíûõ ñèñòåì Netflix Prize1.
I 480 189 ïîëüçîâàòåëåé;
I 17 770 ôèëüìîâ;
I 100 480 507 îöåíîê f1; 2; 3; 4; 5g;
I çàäà÷à: óìåíüøèòü RMSE (ñðåäíå-êâàäðàòè÷íîå
îòêëîíåíèå) c 0.9514 äî 0.8563 (íà 10%);
I 2 îêòÿáðÿ 2006 21 ñåíòÿáðÿ 2009;
1www.netflixprize.com
9
15.
Netflix Prize
Ðàññâåòðåêîìåíäàòåëüíûõ ñèñòåì Netflix Prize1.
I 480 189 ïîëüçîâàòåëåé;
I 17 770 ôèëüìîâ;
I 100 480 507 îöåíîê f1; 2; 3; 4; 5g;
I çàäà÷à: óìåíüøèòü RMSE (ñðåäíå-êâàäðàòè÷íîå
îòêëîíåíèå) c 0.9514 äî 0.8563 (íà 10%);
I 2 îêòÿáðÿ 2006 21 ñåíòÿáðÿ 2009;
I ïðèç $1 000 000.
1www.netflixprize.com
9
Ââåäåíèå â ëèíåéíóþàëãåáðó
I Óìíîæåíèå:
A
nk
B
km
= C
; cij =
nm
Xk
l=1
ailblj
20
45.
Ââåäåíèå â ëèíåéíóþàëãåáðó
I Óìíîæåíèå:
A
nk
B
km
= C
; cij =
nm
Xk
l=1
ailblj
A
nm
Im = In A
nm
= A
nm
20
46.
Ââåäåíèå â ëèíåéíóþàëãåáðó
I Óìíîæåíèå:
A
nk
B
km
= C
; cij =
nm
Xk
l=1
ailblj
A
nm
Im = In A
nm
= A
nm
I Äëèíà (íîðìà) âåêòîðà:
kxk =
Xn
i=1
x2i
!1=2
20
47.
Ââåäåíèå â ëèíåéíóþàëãåáðó
I Óìíîæåíèå:
A
nk
B
km
= C
; cij =
nm
Xk
l=1
ailblj
A
nm
Im = In A
nm
= A
nm
I Äëèíà (íîðìà) âåêòîðà:
kxk =
Xn
i=1
x2i
!1=2
I Ñêàëÿðíîå ïðîèçâåäåíèå:
hx; yi = kxkkyk cos
20
48.
Ââåäåíèå â ëèíåéíóþàëãåáðó
I Óìíîæåíèå:
A
nk
B
km
= C
; cij =
nm
Xk
l=1
ailblj
A
nm
Im = In A
nm
= A
nm
I Äëèíà (íîðìà) âåêòîðà:
kxk =
Xn
i=1
x2i
!1=2
I Ñêàëÿðíîå ïðîèçâåäåíèå:
cos =
hx; yi
kxkkyk
20
49.
Ââåäåíèå â ëèíåéíóþàëãåáðó
I Óìíîæåíèå:
A
nk
B
km
= C
; cij =
nm
Xk
l=1
ailblj
A
nm
Im = In A
nm
= A
nm
I Äëèíà (íîðìà) âåêòîðà:
kxk =
Xn
i=1
x2i
!1=2
I Ñêàëÿðíîå ïðîèçâåäåíèå:
hx; yi =
Xn
i=1
xiyi = xT y
20
Singular Value Decomposition
I Ñèíãóëÿðíîå ðàçëîæåíèå ìàòðèöû:
A
nm
= U
nn
nm
V T
mm
;
U, V îðòîãîíàëüíûå, äèàãîíàëüíàÿ:
UUT = In; V V T = Im;
1; : : : ; min(n;m)
= diag
; 1 : : : min(n;m) 0:
22
53.
Singular Value Decomposition
I Ñèíãóëÿðíîå ðàçëîæåíèå ìàòðèöû:
A
nm
= U
nn
nm
V T
mm
;
U, V îðòîãîíàëüíûå, äèàãîíàëüíàÿ:
UUT = In; V V T = Im;
1; : : : ; min(n;m)
= diag
; 1 : : : min(n;m) 0:
I Óñå÷åííîå ðàçëîæåíèå ðàíãà d:
d+1; : : : ; min(n;m) := 0;
A0
nm
= U0
nd
0
dd
V 0T
dm
A
22
54.
Singular Value Decomposition
I Ñèíãóëÿðíîå ðàçëîæåíèå ìàòðèöû:
A
nm
= U
nn
nm
V T
mm
;
U, V îðòîãîíàëüíûå, äèàãîíàëüíàÿ:
UUT = In; V V T = Im;
1; : : : ; min(n;m)
= diag
; 1 : : : min(n;m) 0:
I Óñå÷åííîå ðàçëîæåíèå ðàíãà d:
d+1; : : : ; min(n;m) := 0;
A0
nm
= U0
nd
0
dd
V 0T
dm
A
I A0 íàèëó÷øåå “íèçêîðàíãîâîå” ïðèáëèæåíèå ñ òî÷êè
çðåíèÿ ñðåäíå-êâàäðàòè÷íîãî îòêëîíåíèÿ.
22
SVD äëÿ ðåêîìåíäàöèé
^rui = hpu; qii
I Âûÿâëåíèå ñêðûòûõ ïðèçíàêîâ îáúåêòîâ è èíòåðåñîâ
ïîëüçîâàòåëåé!
23
58.
SVD äëÿ ðåêîìåíäàöèé
^rui = hpu; qii
I Âûÿâëåíèå ñêðûòûõ ïðèçíàêîâ îáúåêòîâ è èíòåðåñîâ
ïîëüçîâàòåëåé!
I Ïðîáëåìû:
I Ìàòðèöà îöåíîê R íàì ïîëíîñòüþ íå èçâåñòíà.
I Ðàçëîæåíèå íå åäèíñòâåííîå:
(U
)(V
)T = UV T
23
Ãðàäèåíòíûé ñïóñê
t+1= t rJ()
Ïðîáëåìû:
I Ðàáîòàåò î÷åíü ìåäëåííî.
I Íàõîäèò ëîêàëüíûé ìèíèìóì, à íå ãëîáàëüíûé.
27
73.
Alternating Least Squares
I L çàâèñèò îò âñåõ ïàðàìåòðîâ êâàäðàòè÷íî. Ïî êàæäîìó
ïàðàìåòðó ìîæíî íàéòè òî÷íûé îïòèìóì.
28
74.
Alternating Least Squares
I L çàâèñèò îò âñåõ ïàðàìåòðîâ êâàäðàòè÷íî. Ïî êàæäîìó
ïàðàìåòðó ìîæíî íàéòè òî÷íûé îïòèìóì.
I Äëÿ êàæäîãî ïîëüçîâàòåëÿ è äëÿ êàæäîãî îáúåêòà çàäà÷à
îïòèìèçàöèè â òî÷íîñòè ìåòîä íàèìåíüøèõ êâàäðàòîâ.
p
u() = arg min
pu
J() = (QTu
Qu + I)1QTu
ru;
qi
() = arg min
qi
J() = (PTi
Pi + I)1PTi
ri:
28
75.
Alternating Least Squares
I L çàâèñèò îò âñåõ ïàðàìåòðîâ êâàäðàòè÷íî. Ïî êàæäîìó
ïàðàìåòðó ìîæíî íàéòè òî÷íûé îïòèìóì.
I Äëÿ êàæäîãî ïîëüçîâàòåëÿ è äëÿ êàæäîãî îáúåêòà çàäà÷à
îïòèìèçàöèè â òî÷íîñòè ìåòîä íàèìåíüøèõ êâàäðàòîâ.
p
u() = arg min
pu
J() = (QTu
Qu + I)1QTu
ru;
qi
() = arg min
qi
J() = (PTi
Pi + I)1PTi
ri:
I Èòåðàòèâíûé àëãîðèòì ALS:
8u 2 U p2t+1
u = p
u(2t);
8i 2 I q2t+2
i = qi
(2t+1):
28
76.
Alternating Least Squares
I L çàâèñèò îò âñåõ ïàðàìåòðîâ êâàäðàòè÷íî. Ïî êàæäîìó
ïàðàìåòðó ìîæíî íàéòè òî÷íûé îïòèìóì.
I Äëÿ êàæäîãî ïîëüçîâàòåëÿ è äëÿ êàæäîãî îáúåêòà çàäà÷à
îïòèìèçàöèè â òî÷íîñòè ìåòîä íàèìåíüøèõ êâàäðàòîâ.
p
u() = arg min
pu
J() = (QTu
Qu + I)1QTu
ru;
qi
() = arg min
qi
J() = (PTi
Pi + I)1PTi
ri:
I Èòåðàòèâíûé àëãîðèòì ALS:
8u 2 U p2t+1
u = p
u(2t);
8i 2 I q2t+2
i = qi
(2t+1):
I Êàæäûé øàã ìîæíî ðàñïàðàëëåëèòü.
28