ICPSR - Complex Systems Computing - Session 1 - 2011

Introduction to Computing for Complex Systems (Session I) Daniel Martin Katz Michigan State University College of Law

My Affiliations Assistant Professor of Law University of Michigan Center for the Study of Complex Systems PhD Candidate, Political Science & Public Policy

Blog Run with MichaelBommarito II Jon ZelnerCourse slides will bePosted Here!

Goals for the ClassProvide Introduction to Computational andAgent Based Approaches to ModelingContrast Various Approaches HighlightingBenefits and Drawbacks Game Theoretic, Agent Based Models, Network Models, Ecological Models, etc.Provide a Solid Foundation in Implementation Be a Good Consumer of 3rd Party Implementation Actually Implement Models Using Appropriate Software

Introduction toComplex Systems

Key Features of Complex SystemsComplexity and CAS is not chaos theoryBottom up versus Top DownHeterogeneous rather than Homogenous AgentsEmphasizes dependancies between actorsEmphasizes learning and adaptation by actors

Complex Systems Emphasizes Self - organization / lack of top down control Simple behavioral rules generating complex and unforeseen outcomes Non-linearity, Emergence, Positive Feedback

Equilibrium and its Discontents?CAS Focuses upon out of equilibrium solutionsIs a representative agent model appropriate?Is an analytical solution up to the challenge?Does the solution concept scale to the scope ofthe problem?What qualitative justification can be offeredfor assuming something is a fixed point attractor?

Equilibrium and its Discontents?clearly overstated but it is worth rememberingthat a fixed point based solution has limitations When describing what would later be called the nash equlibrium to john von neumann in 1949, von Neumann famously dismissed it with the words, “That’s trivial, you know. That’s just a fixed point theorem.” “A Beautiful Mind” By Sylvia Nasar (1998)

Brief Introduction toAgent Based Modeling

Complex Systems and Agent Based ModelingAgent Based Models are an Approach toStudy Complex Adaptive SystemsHowever, the study of complex systems embracesa number of theoretical and empirical approachesABM’s are only one particular manner toexecute the study of complex systems

Grand Father ofAgent Based Modeling Arguably the Most Important Mind of the 20th Century Invented Game Theory Helped Develop Atomic Bomb Developed the Architecture of the Computer

Father of Agent Based Modeling2005 Nobel Prize WinnerArgues for Bottom UpApproach to Modeling In“Micromotives & Macrobehavior”Outlines the FamousSchelling Segregation Model (aka the ‘Tipping’ Model)

Other Important Contributors John H. ConwayDeveloped the “game of life”a simple cellular automatonLife is a universal cellularautomaton capable ofemulating any turing machine“Game of Life” offers lotsof Important ComplexSystems PrinciplesSimple rules can generateComplex Environments

Other Important Contributors Robert AxelrodOne of the top cited socialscientists in worldHas made many contributionsto the field of agent basedmodelingConsult His Papers Page:http://www-personal.umich.edu/~axe/research_papers.htmlAxelrod & Tesfatsion Guideto Agent Based Models:http://econ2.econ.iastate.edu/tesfatsi/abmread.htm

Other Important ContributorsJoshua Epstein, Robert Axtell, John H. Holland

A Few Major Institutes & Centers

Implementation:From Concept to Product

ImplementationIt is important to understand the canonicalscholarship as highlighted in the lectureHowever, model implementation and the mechanicsof other forms of analysis is often the barrier toentry for most scholarsImplementation is the link between concept andscientific product

Different Software PackagesNetlogo = Introductory Modeling Environment (Agent Based Models & System Dynamics)Vensim / Nova = Development of System Dynamics and Ecological ModelsPajek = Basic Software for Empirical Analysis & Visualization of NetworksR = Platform for Statistical Analysis (Includes the IGraph Library for Networks)Python = Object Oriented Programming Language Flexible and Fast but High Bar to Entry

Getting Started In

Getting Started In NetlogoNetlogo is an Introductory Modeling EnvironmentDeveloped By Uri Wilensky @ Northwestern in 1999Maintained by Center for Connected Learning &Computer-Based Modeling @ Northwestern

Getting Started In NetlogoSyntax is Inherited from the old “Logo” Language Papert & Minsky (1967) Resnick (1991) Wilensky (1999)

Getting Started In NetlogoFeatures Aspects of Programming But is Not aGeneral Language ( C++, Python, Java)Arguably Easier To Learn Than A General LanguageServes the Implementation Needs of Many Modelers

Getting Started In NetlogoAgent Based Models, System Dynamics Models,Network Models, GIS, Etc.Download @ ccl.northwestern.edu/Version 4.1, Version 4.1 3D, Version 3.1.5Should Also Acquire User Manual & Dictionary

Getting Started In Netlogo HIV / AIDS VOTING

Where To Get Help

Netlogo Front Page

Getting Started in Netlogo

Getting Started in Netlogo Files Have a Extension of .nlogo

InterfaceInformationProcedures

Edit theInformation

InterfaceInformationProcedures

Code for theSchelling’sSegregation Model

The Models Library Explore the Available Models

Getting Started in Netlogo

ControlsButtons “once” buttons execute one Action “forever” buttons repeat the same action (Until Stopped)Command Center executes specific commands “on the fly”

Settings Sliders Adjust a quantity by incrementsSwitchers Set a Boolean variable (true/false)Choosers Select a value from a list

ViewsMonitors Offers the Current Value of Variables Plots Displays the Time Series Plot for a Given Variable or Variables

The Netlogo Language

Four Types of Agents Patches Turtles Links The Observer

Patches Tile System with (0,0) Center Origin pxcor min-‐pxcor max-‐pxcor world-‐height world-‐width

View the Settings

View theSettings

View theSettings What is a Torus? Why is It 33 x 33?

Patches: Key ThingsPatches do not move -- they are fixedPatches can have assigned variablesPatches can breed turtlesPatches belong to an agent set

Consulting the Netlogo Dictionary Descriptions of Patch Primitives Can Be Accessed Through the Netlogo Dictionary

TurtlesTurtles move on top of the patchesHave decimal coordinates (xcor, ycor) Have an orientation (heading) Can have different shapes

Turtles Classic Hawk & Dove Model from Evolutionary Game Theory Runs in Netlogo Version 3.1.5

Inspect TurtlesRight Click on a Turtle (Ctrl + Click on Mac)

Watch a Specific TurtleRight Click on a Turtle (Ctrl + Click on Mac)

Lots of Different Turtle Shapes

Turtles: Key ThingsTurtles move around the environmentTurtles can have different variablesTurtles can have various shapesTurtles belong to an agent set

Colorscolor = agentspcolor = patchesSelect a Major Color by Name Customize Colors Using ## from Chart

Next Time: The Forest Fire Model

ICPSR - Complex Systems Computing - Session 1 - 2011

by Daniel Katz on Jul 18, 2011

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ICPSR - Complex Systems Computing - Session 1 - 2011 — Presentation Transcript