Transcript ppt

A RELAXED SYNCHRONIZATION
PRIMITIVE FOR
MACROPROGRAMMING SYSTEMS
TIMOTHY W. HNAT AND KAMIN WHITEHOUSE
[email protected], [email protected]
Presented by: S. M. Shahriar Nirjon
Motivation
Synchronization Problems
State of the Art

Node-level programming techniques (TinyOS)
 Have
little to no synchronization
 Benefits timeliness
 Timeliness
 Sacrifices
– how quickly the system runs
correctness
 Correctness

– how accurate the system is
A fundamental trade-off between timeliness and
correctness.
Macroprogramming
5
Microcode
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Macroprogram
Node-level programming
6
Microcode
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Outline





Synchronization
Exit Conditions
Convergence
Evaluation
Conclusion
Barrier Synchronization
8
1
Node
2
3
4
5
Unreliable and high latency communication
Changes execution timing
Relaxed Synchronization
9
1
Node
2
3
4
5
Control over application concurrency
Relaxed Synchronization
10


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
0
Error
20
Hill Climbing
0
Number of Nodes
100
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)
end
end
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

Relaxed Barriers allow
 Control

Barriers provide a tunable version for WENs
over Timeliness and Accuracy
Provided an algorithm to tune these parameters for
application scenarios
Thank You