Optimization for Atlas Re-active Engine

Dunam Kim, Hokyu Kang, Yangbae Park

Table of Contents

Introduction

• The problems of the basic RE– PUSH only– Too much energy consumption

• Our objectives– To reduce accessing sensors– To fix minor bugs of the basic RE

Evaluation Shortcut

• Finding optimized execution plan of pulling events

• Steps– Enumerate all possible query-evaluation

plans• All possible sequences of evaluation of atomic

events(terminal events)• Equivalent Rules

– Compute the cost for the plans• Probability of each events

– Pick up the plan having the minimum cost

Evaluation Shortcut (cont’d)

• Probability Model– P(event1) = # Occurrence / # Observation– P(~event1) = 1 - P(event1)– P(event1 ∧ event2) = P(event1) * P(event2)

• Example– P(S1(0,100)) * 1 + P(~S1(0,100)) * P(~S2(0,50))

* 2 + P(~S1(0,100)) * P(S2(0,50)) * 3– [S1,S2,S3], [S1,S2,S3]– [S2,S1,S3],[S2,S3,S1]– [S3,S1,S2],[S3,S2,S1]

Evaluation Shortcut (cont’d)• Formal Representation of Cost Calculation

– n• size of atomic events in forms of S(Number) or  S[Number, Number]. n is 3 in

the previous example.

– Integer x • truth value for each sensing event• x = 011 for [S1(0,100) = FALSE, S2(0,50) = TRUE, S3(0,50) = TRUE]

– M(x)• minimum number of evaluation for the case x, x = 100 for [S1(0,100) = TRUE,

S2(0,50) = FALSE, S3(0,50) = FALSE]

– Pi• probability that ith sensing event is true.• For [S1(0,100), S2(0,50), S3(0,50)], P2 = P(S2(0,50))

– B(x, i) • ith bit value of integer x

B(x, i) = (x >> (n-i)) bitwise & 1

– Expected number of evaluation of sensing event is 

Cache System

Atlas Client (Reactive Engine)

History Manager

Cache Manager

Database

Cache System (cont’d)

• Data History Manager– Stores all received data on the database• MySQL + JDBC Driver

– Provides statistical functions• The number of reports in certain period• Average time interval• Range• Standard Deviation• Probability of event

Cache System (cont’d)

• Cache Manager– Tracks each sensor’s stability• Timestamps• Values

– Controls PUSH/PULL mode of a sensor• Additive Increase Multiplicative Decrease al-

gorithm

– Updates out-of-date caches

Cache System (cont’d)

1 2 3 4 5 6 7 8 9 10 11 12 130

20

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Traditional PUSH mode

value

Time

Valu

e

Cache System (cont’d)

0 5 10 15 20 25 30 35 400

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Dynamic PULL mode(Additive Increase)

value

Time

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e

Cache System (cont’d)

0 5 10 15 20 25 30 35 400

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Dynamic PULL mode(Additive Increase)

value

Time

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e