Time-Portable Real-TimeProgramming with Exotasks

Christoph KirschUniversität Salzburg

Joint work with J. Auerbach, D. Bacon, D. Iercan,V.T. Rajan, H. Röck, and R. Trummer

CHESS Seminar, UC Berkeley, February 2007

© C. Kirsch 2007 2

Exotask Eclipse PluginExotaskGraph

Specification

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Exotask Eclipse Plugin

Exotask

Exotask

Exotask

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Exotask Eclipse Plugin

Connection Connection

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Exotask Eclipse PluginTiming

Grammar

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Exotasks in Java

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public class Controller implements Runnable { // Code generated from the specification: private ExotaskInputPort in0; private ExotaskOutputPort out0; public Controller(ExotaskInputPort in0, ExotaskOutputPort out0) { this.in0 = in0; this.out0 = out0; } // Code written by the user: public void run() { double[] sensorData = (double[]) in0.getValue(); out0.setValue( new Double(control(sensorData))); } private double control(double[] sensors) { ... the actual control algorithm ... }}

© C. Kirsch 2007

TT Grammar

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0 1 2 3 4 5 6 7 8 9 10

© C. Kirsch 2007

TT Grammar

4

0 1 2 3 4 5 6 7 8 9 10

Period

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TT Grammar

4

0 1 2 3 4 5 6 7 8 9 10

TimeOffset

TimeOffset

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Logical Execution Time

0 1 2 3 4 5 6 7 8 9 10

Plant

Control System

SensorTask

Actuator

Logical Execution Time

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Actual Execution Time

0 1 2 3 4 5 6 7 8 9 10

Plant

Control System

Sensor

Deadline

ActuatorTask

6

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Actual Execution Time

0 1 2 3 4 5 6 7 8 9 10

Plant

Control System

Sensor

Deadline

ActuatorTask

6

© C. Kirsch 2007

Time PortabilityPlant

Control System

A system’s I/O behavior is input-determined if,for all sequences I of input values and times,

the system always producesunique sequences f(I) of output values and times.

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© C. Kirsch 2007

Exotask Isolation

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Private Heaps

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1. Validate, 2. Instantiate,3. Schedule & Execute

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Exotask Runtime System

public class Controller implements Runnable { // Code generated from the specification: private ExotaskInputPort in0; private ExotaskOutputPort out0; public Controller(ExotaskInputPort in0, ExotaskOutputPort out0) { this.in0 = in0; this.out0 = out0; } // Code written by the user: public void run() { double[] sensorData = (double[]) in0.getValue(); out0.setValue( new Double(control(sensorData))); } private double control(double[] sensors) { ... the actual control algorithm ... }}Exotask Graph

Exotask CodeExotask GraphSpecification

schedule execute

instantiatevalidate

invokes

The JAviator

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50Hz Hard Real Time

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JAviator Controller

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Control Terminal

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Control Terminal Exotask Controller

Demo

Mock JAviator

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IBM’s TuningFork

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TuningFork InstrumentedExotask System

Experiments

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No GC in Progress

17~3ms

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During GC

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1.4GHz Laptop

19~4ms

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Clamp-free Hover

20

Thank you