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CMU SCS Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU

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Page 1: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

Mining Large Social Networks:

Patterns and Anomalies

Christos Faloutsos

CMU

Page 2: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

Thank you

• The Department of Informatics

• Happy 20-th!

• Prof. Yannis Manolopoulos

• Prof. Kostas Tsichlas

• Mrs. Nina Daltsidou

AUTH, May 30, 2012 C. Faloutsos (CMU) 2

Page 3: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

International-caliber friends

among AUTH alumni

• Prof. Evimaria Terzi (U. Boston)

• Prof. Kyriakos Mouratidis (SMU)

• Dr. Michalis Vlachos (IBM)

• …

AUTH, May 30, 2012 C. Faloutsos (CMU) 3

Page 4: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 4

Outline

• Introduction – Motivation

• Problem#1: Patterns in graphs

• Problem#2: Tools

• Problem#3: Scalability

• Conclusions

AUTH, May 30, 2012

Page 5: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 5

Graphs - why should we care?

Internet Map

[lumeta.com]

Food Web

[Martinez ’91]

AUTH, May 30, 2012

$10s of BILLIONS revenue

>500M users

Page 6: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 6

Graphs - why should we care?

• IR: bi-partite graphs (doc-terms)

• web: hyper-text graph

• ... and more:

D1

DN

T1

TM

... ...

AUTH, May 30, 2012

Page 7: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 7

Graphs - why should we care?

• web-log (‘blog’) news propagation

• computer network security: email/IP traffic

and anomaly detection

• ....

• [subject-verb-object: graph]

• Graph == relational table with 2 columns

(src, dst)

• BIG DATA – big graphs

AUTH, May 30, 2012

Page 8: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 8

Outline

• Introduction – Motivation

• Problem#1: Patterns in graphs

– Static graphs

– Weighted graphs

– Time evolving graphs

• Problem#2: Tools

• Problem#3: Scalability

• Conclusions

AUTH, May 30, 2012

Page 9: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 9

Problem #1 - network and graph

mining

• What does the Internet look like?

• What does FaceBook look like?

• What is ‘normal’/‘abnormal’?

• which patterns/laws hold?

AUTH, May 30, 2012

Page 10: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 10

Graph mining

• Are real graphs random?

AUTH, May 30, 2012

Page 11: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 11

Laws and patterns

• Are real graphs random?

• A: NO!!

– Diameter

– in- and out- degree distributions

– other (surprising) patterns

• So, let’s look at the data

AUTH, May 30, 2012

Page 12: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 12

Solution# S.1

• Power law in the degree distribution

[SIGCOMM99]

log(rank)

log(degree)

internet domains

att.com

ibm.com

AUTH, May 30, 2012

Page 13: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 13

Solution# S.1

• Power law in the degree distribution

[SIGCOMM99]

log(rank)

log(degree)

-0.82

internet domains

att.com

ibm.com

AUTH, May 30, 2012

Page 14: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 14

But:

How about graphs from other domains?

AUTH, May 30, 2012

Page 15: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 15

More power laws:

• web hit counts [w/ A. Montgomery]

Web Site Traffic

in-degree (log scale)

Count

(log scale) Zipf

users sites

``ebay’’

AUTH, May 30, 2012

Page 16: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

And numerous more

• Who-trusts-whom (epinions.com)

• Income [Pareto] –’80-20 distribution’

• Duration of downloads [Bestavros+]

• Duration of UNIX jobs (‘mice and

elephants’)

• Size of files of a user

• …

• ‘Black swans’

AUTH, May 30, 2012 C. Faloutsos (CMU) 16

Page 17: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 17

Outline

• Introduction – Motivation

• Problem#1: Patterns in graphs

– Static graphs

• degree, diameter, eigen,

• Triangles

– Time evolving graphs

• Problem#2: Tools

AUTH, May 30, 2012

Page 18: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 18

Solution# S.3: Triangle ‘Laws’

• Real social networks have a lot of triangles

AUTH, May 30, 2012

Page 19: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 19

Solution# S.3: Triangle ‘Laws’

• Real social networks have a lot of triangles

– Friends of friends are friends

• Any patterns?

AUTH, May 30, 2012

Page 20: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 20

Triangle Law: #S.3 [Tsourakakis ICDM 2008]

SN Reuters

Epinions X-axis: degree

Y-axis: mean # triangles

n friends -> ~n1.6 triangles

AUTH, May 30, 2012

Page 21: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

Triangle counting for large graphs?

Anomalous nodes in Twitter(~ 3 billion edges)

[U Kang, Brendan Meeder, +, PAKDD’11]

21 AUTH, May 30, 2012 21 C. Faloutsos (CMU)

Page 22: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

Triangle counting for large graphs?

Anomalous nodes in Twitter(~ 3 billion edges)

[U Kang, Brendan Meeder, +, PAKDD’11]

22 AUTH, May 30, 2012 22 C. Faloutsos (CMU)

Page 23: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

Triangle counting for large graphs?

Anomalous nodes in Twitter(~ 3 billion edges)

[U Kang, Brendan Meeder, +, PAKDD’11]

23 AUTH, May 30, 2012 23 C. Faloutsos (CMU)

Page 24: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 24

Outline

• Introduction – Motivation

• Problem#1: Patterns in graphs

– Static graphs

– Time evolving graphs

• Problem#2: Tools

• …

AUTH, May 30, 2012

Page 25: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 25

Problem: Time evolution

• with Jure Leskovec (CMU ->

Stanford)

• and Jon Kleinberg (Cornell –

sabb. @ CMU)

AUTH, May 30, 2012

Page 26: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 26

T.1 Evolution of the Diameter

• Prior work on Power Law graphs hints

at slowly growing diameter:

– diameter ~ O(log N)

– diameter ~ O(log log N)

• What is happening in real data?

AUTH, May 30, 2012

Page 27: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 27

T.1 Evolution of the Diameter

• Prior work on Power Law graphs hints

at slowly growing diameter:

– diameter ~ O(log N)

– diameter ~ O(log log N)

• What is happening in real data?

• Diameter shrinks over time

AUTH, May 30, 2012

Page 28: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 28

T.1 Diameter – “Patents”

• Patent citation

network

• 25 years of data

• @1999

– 2.9 M nodes

– 16.5 M edges

time [years]

diameter

AUTH, May 30, 2012

Page 29: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 29

Outline

• Introduction – Motivation

• Problem#1: Patterns in graphs

• Problem#2: Tools

– Belief Propagation

• Problem#3: Scalability

• Conclusions

AUTH, May 30, 2012

Page 30: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

AUTH, May 30, 2012 C. Faloutsos (CMU) 30

E-bay Fraud detection

w/ Polo Chau &

Shashank Pandit, CMU

[www’07]

Page 31: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

AUTH, May 30, 2012 C. Faloutsos (CMU) 31

E-bay Fraud detection

Page 32: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

AUTH, May 30, 2012 C. Faloutsos (CMU) 32

E-bay Fraud detection

Page 33: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

AUTH, May 30, 2012 C. Faloutsos (CMU) 33

E-bay Fraud detection - NetProbe

Page 34: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

Popular press

And less desirable attention:

• E-mail from ‘Belgium police’ (‘copy of

your code?’)

AUTH, May 30, 2012 C. Faloutsos (CMU) 34

Page 35: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 35

Outline

• Introduction – Motivation

• Problem#1: Patterns in graphs

• Problem#2: Tools

• Problem#3: Scalability -PEGASUS

• Conclusions

AUTH, May 30, 2012

Page 36: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

AUTH, May 30, 2012 C. Faloutsos (CMU) 36

Scalability

• Google: > 450,000 processors in clusters of ~2000

processors each [Barroso, Dean, Hölzle, “Web Search for

a Planet: The Google Cluster Architecture” IEEE Micro

2003]

• Yahoo: 5Pb of data [Fayyad, KDD’07]

• Problem: machine failures, on a daily basis

• How to parallelize data mining tasks, then?

• A: map/reduce – hadoop (open-source clone) http://hadoop.apache.org/

Page 37: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 37

Outline

• Introduction – Motivation

• Problem#1: Patterns in graphs

• Problem#2: Tools

• Problem#3: Scalability –PEGASUS

– Radius plot

• Conclusions

AUTH, May 30, 2012

Page 38: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

HADI for diameter estimation

• Radius Plots for Mining Tera-byte Scale

Graphs U Kang, Charalampos Tsourakakis,

Ana Paula Appel, Christos Faloutsos, Jure

Leskovec, SDM’10

• Naively: diameter needs O(N**2) space and

up to O(N**3) time – prohibitive (N~1B)

• Our HADI: linear on E (~10B)

– Near-linear scalability wrt # machines

– Several optimizations -> 5x faster

C. Faloutsos (CMU) 38 AUTH, May 30, 2012

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CMU SCS

????

19+ [Barabasi+]

39 C. Faloutsos (CMU)

Radius

Count

AUTH, May 30, 2012

~1999, ~1M nodes

Page 40: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

YahooWeb graph (120Gb, 1.4B nodes, 6.6 B edges)

• Largest publicly available graph ever studied.

????

19+ [Barabasi+]

40 C. Faloutsos (CMU)

Radius

Count

AUTH, May 30, 2012

??

~1999, ~1M nodes

Page 41: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

YahooWeb graph (120Gb, 1.4B nodes, 6.6 B edges)

• Largest publicly available graph ever studied.

????

19+? [Barabasi+]

41 C. Faloutsos (CMU)

Radius

Count

AUTH, May 30, 2012

14 (dir.)

~7 (undir.)

Page 42: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

YahooWeb graph (120Gb, 1.4B nodes, 6.6 B edges)

•7 degrees of separation (!)

•Diameter: shrunk

????

19+? [Barabasi+]

42 C. Faloutsos (CMU)

Radius

Count

AUTH, May 30, 2012

14 (dir.)

~7 (undir.)

Page 43: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

YahooWeb graph (120Gb, 1.4B nodes, 6.6 B edges)

Q: Shape?

????

43 C. Faloutsos (CMU)

Radius

Count

AUTH, May 30, 2012

~7 (undir.)

Page 44: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

44 C. Faloutsos (CMU)

YahooWeb graph (120Gb, 1.4B nodes, 6.6 B edges)

• effective diameter: surprisingly small.

• Multi-modality (?!) AUTH, May 30, 2012

Page 45: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

Radius Plot of GCC of YahooWeb.

45 C. Faloutsos (CMU) AUTH, May 30, 2012

Page 46: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

46 C. Faloutsos (CMU)

YahooWeb graph (120Gb, 1.4B nodes, 6.6 B edges)

• effective diameter: surprisingly small.

• Multi-modality: probably mixture of cores . AUTH, May 30, 2012

Page 47: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

47 C. Faloutsos (CMU)

YahooWeb graph (120Gb, 1.4B nodes, 6.6 B edges)

• effective diameter: surprisingly small.

• Multi-modality: probably mixture of cores . AUTH, May 30, 2012

EN

~7

Conjecture:

DE

BR

Page 48: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

48 C. Faloutsos (CMU)

YahooWeb graph (120Gb, 1.4B nodes, 6.6 B edges)

• effective diameter: surprisingly small.

• Multi-modality: probably mixture of cores . AUTH, May 30, 2012

~7

Conjecture:

Page 49: Mining large graphs - Aristotle University of Thessaloniki · 2015-03-20 · Mining Large Social Networks: Patterns and Anomalies Christos Faloutsos CMU . CMU SCS Thank you • The

CMU SCS

C. Faloutsos (CMU) 49

Outline

• Introduction – Motivation

• Problem#1: Patterns in graphs

• Problem#2: Tools

• Problem#3: Scalability

• Conclusions

AUTH, May 30, 2012

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CMU SCS

C. Faloutsos (CMU) 50

OVERALL CONCLUSIONS –

low level:

• Several new patterns (shrinking diameters,

triangle-laws, etc)

• New tools:

– Fraud detection (belief propagation)

• Scalability: PEGASUS / hadoop

AUTH, May 30, 2012

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CMU SCS

C. Faloutsos (CMU) 51

OVERALL CONCLUSIONS –

medium-level

• BIG DATA: Large datasets reveal patterns/outliers that are invisible otherwise

AUTH, May 30, 2012

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CMU SCS

C. Faloutsos (CMU) 52

Project info

Akoglu,

Leman

Chau,

Polo

Kang, U McGlohon,

Mary

Tong,

Hanghang

Prakash,

Aditya

AUTH, May 30, 2012

Thanks to: NSF IIS-0705359, IIS-0534205,

CTA-INARC; Yahoo (M45), LLNL, IBM, SPRINT,

Google, INTEL, HP, iLab

www.cs.cmu.edu/~pegasus

Koutra,

Danae

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CMU SCS

Thank you for the honor!

• Congratulations for 20-th anniversary

and…

AUTH, May 30, 2012 C. Faloutsos (CMU) 53

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CMU SCS

High-level conclusion:

Collaborations

• Sociology + CS (triangles)

• Civil engineering + CS (sensor placement)

• fMRI/medical + graphs (medical db’s)

• …

AUTH, May 30, 2012 C. Faloutsos (CMU) 54

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CMU SCS

Never stop learning

AUTH, May 30, 2012 C. Faloutsos (CMU) 55

Socrates Plato Aristotle

GHRASKW AEI DIDASKOMENOS