the empirical process - agile alliance

The Empirical Process

- at the very core of agile

Daniel Brolund @danielbrolund [email protected]

mailto:[email protected]




Daniel Brolund — @danielbrolund — [email protected] Brolund — @danielbrolund — [email protected]

An everyday empirical process...





Me





Me

Do I jump in...?





Schematic: Me

Do I jump in...?





Desired

Schematic: Me

Do I jump in...?





Desired

Desired

Schematic: Me

Do I jump in...?





Desired

Desired

Controller

Schematic: Me

Do I jump in...?





ControllerDesired

Desired

Controller

Schematic: Me

Do I jump in...?





ControllerDesired

Desired

Systeminput

Controller

Schematic: Me

Do I jump in...?





ControllerDesired

Systeminput

Desired

Systeminput

Controller

Schematic: Me

Do I jump in...?





ControllerDesired

Systeminput

Desired

Systeminput

Controller

System

Schematic: Me

Do I jump in...?





Controller SystemDesired

Systeminput

Desired

Systeminput

Controller

System

Schematic: Me

Do I jump in...?





Controller SystemDesired

Systeminput

Desired

Systeminput

ActualController

System

Schematic: Me

Do I jump in...?





Controller SystemActualDesired

Systeminput

Desired

Systeminput

ActualController

System

Schematic: Me

Do I jump in...?






Systeminput

Desired

Systeminput

ActualController

System

Feed-forward or Open-loop system

Schematic: Me

Do I jump in...?





Actual==Desired ?


Systeminput

Desired

Systeminput

ActualController

System


Schematic: Me

Do I jump in...?





Actual==Desired ?


Systeminput

Desired

Systeminput

ActualController

System


Time

Schematic: MeTemp

Do I jump in...?





Actual==Desired ?


Systeminput

Desired

Systeminput

ActualController

System


Time

Desired

Schematic: MeTemp

Do I jump in...?





Actual==Desired ?


Systeminput

Desired

Systeminput

ActualController

System

Feed-forward or Open-loop system Actual

Time

Desired

Schematic: MeTemp

Do I jump in...?





Actual==Desired ?


Systeminput

Desired

Systeminput

ActualController

System

Feed-forward or Open-loop system ?Actual

Time

Desired

Schematic: MeTemp

Do I jump in...?



Daniel Brolund — @danielbrolund — [email protected]

Exercise on feed-forward systems




Drop-zone





Drop-zone

Robot





Drop-zone

RobotController





Drop-zone

RobotController


↑↰

P

↱

D

↑

↑




Drop-zone

Tracker

RobotController


↑↰

P

↱

D

↑

↑




Drop-zone

Tracker

RobotController

Tracker counts paper balls in dropzone as a function of time


↑↰

P

↱

D

↑

↑




Drop-zone

Tracker

RobotController

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured



↑↰

P

↱

D

↑

↑




Drop-zone

Tracker

RobotController

Goal: Meet desired nr of paper balls in dropzone (see graph)

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured



↑↰

P

↱

D

↑

↑




What is the control error?




Time

What is the control error?Temp




Time

Desired





Actual

Time

Desired





Actual

Time

Desired


"Error surface"




Actual

Time

Desired

Control Error = ∫|Desired-Actual|


"Error surface"




Actual

Time

Desired



"Error surface"

Time

Control error




Actual

Time

Desired



"Error surface"

Time

Control error∞




Points of Discussion - groups of 4-6




Results in exercise? Error?






What are the measurements we make?







Impact of robot precision?







What are the unknowns?









Sensitivity to unknowns & changes? Robustness?










Impact of robot precision? Iteration length?










What are the delays?












Impact of iteration length?










Similarities with software development?






The "simplistic" solution


Systeminput






Systeminput Controller=(System)-1







⇒Desired = Actual







⇒Desired = Actual

Requires: - detailed knowledge of System, Desired and hence Actual - that such a Controller exists and can create such System input- that the System can handle System input







⇒Desired = Actual


Errorsε







⇒Desired = Actual


Errorsε

"Unlimited"energy

∞







⇒Desired = Actual


Errorsε

Change"Unlimited"

energy

∞







⇒Desired = Actual


Errorsε

Change"Unlimited"

energy

∞

Complexity







⇒Desired = Actual


Errorsε

Change"Unlimited"

energy

∞

Complexity

Won't work in reality




Adding feedback!

Systeminput

ActualController

Me

Desired

System




Schematic:


Systeminput


Adding feedback!

Systeminput

ActualController

Me

Desired

System




Schematic:


Systeminput


Adding feedback!

Sensor

Systeminput

ActualController

Me

Desired

System




Schematic:


Systeminput


Adding feedback!

Sensor

Observed result

Systeminput

ActualController

Me

Desired

System




Schematic:


Systeminput


Adding feedback!

Sensor

SensorObserved result

Observed result

Systeminput

ActualController

Me

Desired

System




Schematic:


Systeminput


Adding feedback!

Sensor

Error-


Observed result

Systeminput

ActualController

Me

Desired

System




Schematic:


Systeminput


Adding feedback!

Feed-back or Closed-loop system

Sensor

Error-


Observed result

Systeminput

ActualController

Me

Desired

System




Schematic:


Systeminput


Adding feedback!


Sensor

Error-


Time

Temp

Observed result

Systeminput

ActualController

Me

Desired

System




Schematic:


Systeminput


Adding feedback!


Sensor

Error-


Time

Desired

Temp

Observed result

Systeminput

ActualController

Me

Desired

System




Schematic:


Systeminput


Adding feedback!


Sensor

Error-

SensorObserved result Actual

Time

Desired

Temp

Observed result

Systeminput

ActualController

Me

Desired

System




Drop-zone

Tracker

Robot

Controller

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured

Exercise on feed-back systems




Drop-zone

Tracker

Robot

Controller

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured

Exercise on feed-back systemsAs before, but now

only one step at a time!




Drop-zone

Tracker

Robot

Controller

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured


↑

As before, but now only one step at a time!




Drop-zone

Tracker

Robot

Controller

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured


↑↰





Drop-zone

Tracker

Robot

Controller

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured


↑↰↑





Drop-zone

Tracker

Robot

Controller

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured


↑↰

P

↑





Drop-zone

Tracker

Robot

Controller

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured


↑↰

P

↱

↑





Drop-zone

Tracker

Robot

Controller

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured


↑↰

P

↱

↑

↑





Drop-zone

Tracker

Robot

Controller

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured


↑↰

P

↱

D

↑

↑





What is the control error now?





Actual

Desired

Temp






Time

Control error

Actual

Desired

Temp






Actual

Time

Control error

Actual

Desired

Temp






Actual

Time

Control error

bounded!!

Actual

Desired

Temp




Observability and controllability




Error- Controller System

ActualDesired

Systeminput



-





ActualDesired

Systeminput


Uncontrollable


-





ActualDesired

Systeminput


Uncontrollable

Unobservable


-




The Sensor has to measure

a relevant state (observability) that the

Controller can influence (controllability).


ActualDesired

Systeminput


Uncontrollable

Unobservable


-








ActualDesired

Systeminput


Uncontrollable

Unobservable


Water temperature

-








ActualDesired

Systeminput


Uncontrollable

Unobservable


Water temperature

Flow

-








ActualDesired

Systeminput


Uncontrollable

Unobservable


Water temperature

Flow Acidity

-








ActualDesired

Systeminput


Uncontrollable

Unobservable


Water temperature

Mineral tracesFlow Acidity

-








ActualDesired

Systeminput


Uncontrollable

Unobservable


Water temperature

Mineral traces

Radioactivity

Flow Acidity

-








ActualDesired

Systeminput


Uncontrollable

Unobservable


Water temperature

Mineral traces

Radioactivity

Flow Acidity

-

SW







Lines of code


ActualDesired

Systeminput


Uncontrollable

Unobservable


Water temperature

Mineral traces

Radioactivity

Flow Acidity

-

SW







Lines of code

Unit test results


ActualDesired

Systeminput


Uncontrollable

Unobservable


Water temperature

Mineral traces

Radioactivity

Flow Acidity

-

SW







Lines of code

Unit test results


ActualDesired

Systeminput


Uncontrollable

Unobservable


ROI

Water temperature

Mineral traces

Radioactivity

Flow Acidity

-

SW







Lines of code

Unit test results

Acceptance test results


ActualDesired

Systeminput


Uncontrollable

Unobservable


ROI

Water temperature

Mineral traces

Radioactivity

Flow Acidity

-

SW







Lines of code

Unit test results


Nr of checkins


ActualDesired

Systeminput


Uncontrollable

Unobservable


ROI

Water temperature

Mineral traces

Radioactivity

Flow Acidity

-

SW







Lines of code

Unit test results


Nr of checkins Request statistics


ActualDesired

Systeminput


Uncontrollable

Unobservable


ROI

Water temperature

Mineral traces

Radioactivity

Flow Acidity

-

SW







Lines of code

Unit test results




ActualDesired

Systeminput


Uncontrollable

Unobservable


User satisfaction

ROI

Water temperature

Mineral traces

Radioactivity

Flow Acidity

-

SW







Lines of code

Unit test results




ActualDesired

Systeminput


Uncontrollable

Unobservable


User satisfactionUsability

ROI

Water temperature

Mineral traces

Radioactivity

Flow Acidity

-

SW




There are many feedback loops at play!




Live user feedback/release





Live user feedback/release Usability tests





Retrospective






Retrospective


Whiteboard discussions





Daily stand-up

Retrospective







ATDD

Daily stand-up

Retrospective







TDD

ATDD

Daily stand-up

Retrospective







TDD

ATDD

Daily stand-up

Retrospective


Pairing






TDD

ATDD

Daily stand-up

Retrospective


Compilation Pairing






SquigglesTDD

ATDD

Daily stand-up

Retrospective


Compilation Pairing






Feedback cycle-time sweet-spots are different due to

processing and delays

SquigglesTDD

ATDD

Daily stand-up

Retrospective


Compilation Pairing








SquigglesTDD

ATDD

Daily stand-up

Retrospective


Compilation Pairing



too slow ⇒

Unstable system






SquigglesTDD

ATDD

Daily stand-up

Retrospective


Compilation Pairing



too slow ⇒

Unstable system

too fast ⇒

Controller overloaded or too expensive




Error- Controller SystemActualDesired

Systeminput


Is feed-forward waste?

-





Systeminput


Feed-forward using the Controller is application of a priori knowledge.

We always need some of it to avoid re-inventing wheels.


-





Systeminput




TDD


-





Systeminput




TDD

ATDD


-





Systeminput




TDD

ATDD Daily standups


-





Systeminput




TDD

ATDD

Iterations

Daily standups


-





Systeminput




TDD

ATDD

Iterations

Daily standups Continuous integration


-





Systeminput




TDD

ATDD

Iterations


Retrospectives


-





Systeminput




TDD

ATDD

Iterations


Deployment environments

Retrospectives


-




The impact of delay

Systeminput

ActualController

System

Sensor

Me

Desired




The impact of delay

Systeminput

ActualController

System

Sensor

Error

-

Schematic:


Systeminput


-

Me

Desired




The impact of delay

Systeminput

ActualController

System

Sensor

Delay

Error

-

Schematic:


Systeminput


-

Me

Desired




The impact of delay

Systeminput

ActualController

System

Sensor

Delay

Error

-

Schematic:


Systeminput


-

Me

Desired

Delay




The impact of delay

Systeminput

ActualController

System

Sensor

Time

Temp

Delay

Error

-

Schematic:


Systeminput


-

Me

Desired

Delay




The impact of delay

Systeminput

ActualController

System

Sensor

Time

Desired

Temp

Delay

Error

-

Schematic:


Systeminput


-

Me

Desired

Delay




The impact of delay

Systeminput

ActualController

System

Sensor

Time

Desired

Temp

Delay

Tap temp

Error

-

Schematic:


Systeminput


-

Me

Desired

Delay




The impact of delay

Systeminput

ActualController

System

Sensor

Time

Desired

Temp

Delay

Tap temp

Tap tempError

-

Schematic:


Systeminput


-

Me

Desired

Delay




The impact of delay

Systeminput

ActualController

System

Sensor

Time

Desired

Temp

Delay

Tap temp

Tap temp

Tap temp

Error

-

Schematic:


Systeminput


-

Me

Desired

Delay




The impact of delay

Systeminput

ActualController

System

Sensor

Observed result

Time

Desired

Temp

Delay

Tap temp

Tap temp

Tap temp

Error

-

Schematic:


Systeminput


-

Me

Desired

Delay




Drop-zone

Tracker

RobotController

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured

Exercise on feed-back system with delay




Drop-zone

Tracker

RobotController

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured

Exercise on feed-back system with delayAs before, but now now three steps at a

time!




Drop-zone

Tracker

RobotController

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured


↑

As before, but now now three steps at a

time!




Drop-zone

Tracker

RobotController

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured


↑↰


time!




Drop-zone

Tracker

RobotController

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured


↑↰↑


time!




Drop-zone

Tracker

RobotController

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured


↑↰

P

↑


time!




Drop-zone

Tracker

RobotController

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured


↑↰

P

↱

↑


time!




Drop-zone

Tracker

RobotController

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured


↑↰

P

↱

↑

↑


time!




Drop-zone

Tracker

RobotController

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured


↑↰

P

↱

D

↑

↑


time!




Drop-zone

Tracker

RobotController

0

5

10

0 20 40 60 80 100

Time (s)

DesiredMeasured


↑↰

P

↱

D

↑

↑


time!

Place sequence on back of Robot (FIFO queue). Give the first step to the robot, and add one step last in the queue.




Delay considerations




Observed result

Desired

Temp

Tap temp





Observed result

Desired

Temp

Tap temp


delay > half of required cycletime ⇒

Guaranteed instability!(in practice, instability comes earlier)




Observed result

Desired

Temp

Tap temp




It often takes about 5-10 times the delay to tune the

system




Observed result

Desired

Temp

Tap temp





system

Error

- Controller SystemActualDesired

Systeminput

Sensor

Observed result

-




Observed result

Desired

Temp

Tap temp





system

Error


Systeminput

Sensor

Observed result

Delay position in loop is irrelevant w.r.t. instability!

-




Observed result

Desired

Temp

Tap temp





system

Error


Systeminput

Sensor

Observed result

DelayDelay position in loop is irrelevant w.r.t. instability!

-




Observed result

Desired

Temp

Tap temp





system

Error


Systeminput

Sensor

Observed result


-

Delay




Observed result

Desired

Temp

Tap temp





system

Error


Systeminput

Sensor

Observed result

Delay


-




Observed result

Desired

Temp

Tap temp





system

Error


Systeminput

Sensor

Observed result

DelayDelay position in loop is irrelevant w.r.t. instability!

-




Noise




Signal

Noise




+

NoiseSignal

Noise




+ =

Huh?NoiseSignal

Noise




+ =

Huh?NoiseSignal

Signals must be filtered from noise. ⇒ Delays

⇒ Lower communication bandwidth

Noise




+ =

Huh?NoiseSignal

Signals must be filtered from noise. ⇒ Delays

⇒ Lower communication bandwidth

Noise

In SW-development, noise can be - Irrelevant information - Disinformation




• What does the following do to your control system?

• Trust?

• Distrust?

• Lies?

• Care?

• What is noise according to you?

• What other "soft" issues will affect the system? How?

"Softer" issues - discussion in groups


Systeminput


-




• How can you break the empirical process? What part?

• Controller?

• System?

• Sensor?

• Desired?

Failure modes - discussion in groups


Systeminput


-




• Introduce feedback where appropriate!

• Apply reasonable amount of a priori (feed-forward) knowledge.

• Tune the Sensors to improve resolution.

• Remove unnecessary Sensoring.

• Find the iteration cycle-time sweet-spot.

• Reduce delays to improve responsiveness, extend margins, or cheapen the Controller.

• Reduce noise.

Conclusions & advice



the empirical process - agile alliance

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