google search & pagerank: a case study

8/7/2019 Google Search & PageRank: A Case Study

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GOOGLE SEARCH & PAGERANK-A CASE STUDY

Presented by:Gaurav Kumar Srivastava


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OVERVIEW

Worl wi w

oogl on w

How googl works

oogl s rch

ger nk lgorith

Iss es in p ger nk

concl sion


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WORLD WIDE WEB

WWW is HU E. Approxi teesti tions :

~50 illion ctive web sites

~25 billion web p ges

~1 billion sers

There re l rgenumber ofsearch engines too :

At least 3,105 search engines


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GOOGLE ON WEB


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HOW GOOGLE WORKS?

What happens when I enter a search at oogle ?


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GOOGLE SEARCH

Google consists of three istinct parts with fast parallelprocessing.

GooglebotGooglebot, a web crawler that finds and fetches webpages.

The IndexerIndexer that sorts every word on every page andstores the resulting indexofwords ina hugedatabase.

The Query rocessorQuery rocessor, which compares your search queryto the index and recommends the documents that itconsiders most relevant.


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SEARCH ENGINE

ARCHITECTURE


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TECHNOLOGY ASPECT


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ANATOMY OF A SEARCH ENGINE

WWW

User Query

Crawler Module

Page

Repository

Indexing

Module

Indexes

Ranking

ModuleQuery

Module

Results


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RANKING MODULE

Key is tofindthose pages thattheuser desires

Takes a setofrelevant web pages and ranks them

Rank is generally afunctionof:

Content core &

Popularity core (Thefocus ofthis talk)

E.g. What are some good Indian restaurants in Toronto?


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PIGEONRANK

PigeonRankPigeonRank OverviewOverview

The heart of Google's search technology is PigeonRank, asystem for ranking web pages developed by Google founders

Larry Page and ergey Brin at tanford University.

low cost pigeon clusters (PCs) could be used to compute therelative value of web pages faster than human editors or

machine-basedalgorithms.


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PAGERANK AGORITHM

PageRankalgorithm, givenbyergey Brin and Larry Page in 1998

Exploits the linked structureofthewebfor computingpopularity

PR(A) = (1-d) + d (PR(T1)/C(T1) +

... + PR(Tn)/C(Tn))

PR(A) is thePageRank ofpage A,

PR(Ti) is thePageRank ofpages Ti

which link to page A,C(Ti) is thenumber ofoutbound

links on page Ti and

d is adampingfactor which canbe

setbetween 0 and 1.


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PAGERANK DEFINITION(CONT..)

So, firstofall,we seethatPageRank does not rank

web sites as a whole, but is determinedfor each page

individually.

Further,the PageRank ofpage A is recursively defined

by thePageRanks ofthose pages which link to page A.


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The Characteristics of PageRank

AveragePageRank ofa web page is 1.

TheminimumPageRank ofa page is givenby (1-d).

Therefore, there is amaximumPageRank for a page

which is givenby dN+(1-d), whereN is total number of

web pages.


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PAGERANK: ISSUES

PageRank is quite sensitiveto small changes inthe

web.Google computes PageRank from scratch every

month!

PageRank is Query Independent, Itmeans thattobe

better linked is more importantthanto containthesearch terms !


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CONCLUSION..

GooglePageRank is probably oneofthemost importantalgorithms

ever developedfor theWeb.

MostofGoogle's popularity is creditedto its preferredformofsearch

engineoptimization, atrademarked programGoogledubbed

PageRank. WhenPageRank was patentedthe patent was assigned

toStanford University.

PageRank, only oneofhundreds offactors usedby Googleto

determinebest search results, helps to keep our search cleanand

efficient.


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QUERIES

?


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THANK YOU & KEEP

GOOGLING

google search & pagerank: a case study

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