A RELAXED SYNCHRONIZATION PRIMITIVE

FORMACROPROGRAMMING

SYSTEMS

Presented by: S. M. Shahriar Nirjon

TIMOTHY W. HNAT AND KAMIN WHITEHOUSE

HNAT@CS.VIRGINIA.EDU, WHITEHOUSE@CS.VIRGINIA.EDU

Motivation

Synchronization Problems

State of the Art Node-level programming techniques

(TinyOS) Have little to no synchronization Benefits timeliness

Timeliness – how quickly the system runs Sacrifices correctness

Correctness – how accurate the system is A fundamental trade-off between

timeliness and correctness.

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Microcode

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Macroprogramming

Macroprogram

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Microcode

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Node-level programming

Outline Synchronization Exit Conditions Convergence Evaluation Conclusion

8

Barrier Synchronization

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Node

Unreliable and high latency communication

Changes execution timing

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Relaxed Synchronization

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Node

Control over application concurrency

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Relaxed Synchronization Allows the programmer to control the

amount of parallelism Tradeoff between timeliness and

accuracy Timeliness – how quickly the system runs Accuracy – how close the measurements

are to the real world

Exit Conditions Nodes Radius Deadline

Brute Force Search Enumerate all combinations of Nodes,

Radius, and Deadline Typically a very large search space

Brute force search Guaranteed to discover the optimal solution

given enough time Extremely slow to run

Hill ClimbingEr

ror

Number of Nodes0

0

100

20

Experimental Setup Object Tracking Application

Simulation

every(1) magVals = magSensors.sense() RB(NODES,DEADLINE,RADIUS,fitness) active = find(sum(neighborMag>500,2)>3) maxNeighbor = max(neighborMag, 2) leaders = find(maxNeighbor(active)==magVal(active)) pos = weightedAverage(neighborMag) if leaders focusCamera(pos) endend

Experimental Setup Object Tracking Application

Simulation Five Scenarios

Single target Two targets Fast-moving target High-density deployment False-positive errors

Results – Distance Error

Results – Parameter Variations

Results – 3d Surface

Conclusion Macroprogramming abstractions

typically have an expectation of sequential-like semantics Relaxed Barriers provide a tunable version

for WENs Relaxed Barriers allow

Control over Timeliness and Accuracy Provided an algorithm to tune these

parameters for application scenarios

Thank You