The repast framework and social simulations
1 / 41

The RePast Framework and Social Simulations - PowerPoint PPT Presentation

  • Uploaded on

The RePast Framework and Social Simulations. Presented by Tim Furlong. Overview. RePast Social Simulations Simulations implemented with RePast Santa Fe Artificial Stock Market Endogenizing Geopolitical Boundaries. RePast. REcursive Porous Agent Simulation Toolkit Java class library

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about ' The RePast Framework and Social Simulations' - keith-schultz

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript


  • RePast

  • Social Simulations

  • Simulations implemented with RePast

    • Santa Fe Artificial Stock Market

    • Endogenizing Geopolitical Boundaries


  • REcursive Porous Agent Simulation Toolkit

  • Java class library

  • University of Chicago

    • Social Science Research Computing

Repast framework
RePast: Framework

  • Base classes to be extended

    • Engine class

    • Agent class

    • Environment class

    • GUI displays, charts, graphs

  • Utility classes

    • Spatial representations

    • Statistical RNGs

The repast framework and social simulations

  • Generic approach

    • Discrete event simulator

  • Easy implementation

    • SugarScape(partial) : ~ 650 LOC

    • Game of Life : ~ 750 LOC

Repast advantages
RePast: Advantages

  • Facilitates implementation

    • Convenient representation of heterogeneous agents

    • Support for geometric world models

    • Garbage collection

  • ‘Powerful’ visualization techniques

    Lars-Erik Cederman, “Endogenizing Geopolitical Boundaries with Agent-based Modeling”, prepared for Sackler Colloquium on “Adaptive Agents, Intelligence, and Emergent Human Organization: Capturing Complexity through Agent-based Modelling”, Oct. 2001.

Repast applications
RePast: Applications

  • School voucher programs

  • Consumer choice

  • Decision making in closed regimes

  • Modeling the size of wars

  • Voting dynamics

  • Self-organizing computer networks

  • Multi-cellular tumors

    Repast Homepage – Projects and Publications :

Social simulations
Social Simulations

  • Goal is to simulate observed behaviors with hypothesized model

  • Several ‘flavors’ of simulation

    • Statistical : global variables

    • Agent-based : allows heterogeneous agents with varied and dynamic behavior

Sfi asm introduction
SFI-ASM: Introduction Corrections

  • Simplistic stock market simulation

  • Isolates learning speed of traders as critical parameter

  • Based on original SFI-ASM

  • Fixes faulty mutation operator

    • Results not quite as compelling

  • Interesting RePast model

Sfi asm original model
SFI-ASM: Original Model Corrections

  • N traders

    • 1 unit risky stock, 20 000 units cash

  • Each trader seeks to buy or sell stock based on expectations of profit

  • Profit

    • Fixed return of rf on cash assets

    • Stock pays stochastic dividend

Sfi asm stock
SFI-ASM: Stock Corrections

  • Only one ‘stock’ in market

  • Stock has price pt and dividend dt

  • Dividend of stock at time t +1

  • Mean-reverting factor of (1 – ρ), but generally stochastic

Sfi asm traders
SFI-ASM: Traders Corrections

  • Risk aversion factor of λi

  • Wealth at time t of Wi,t: stock + cash

  • Optimal amount of stock based on expectations of profit

Sfi asm expectation rules
SFI-ASM: Expectation rules Corrections

  • Market has descriptor Dt

    • Bitstring of market conditions

  • Each trader has own set of 100 rules

  • Rule comprised of:

    • Condition

    • Forecast

    • Forecast accuracy

    • Fitness value

The repast framework and social simulations

The repast framework and social simulations

Sfi asm rule evolution
SFI-ASM: Rule Evolution Corrections

  • Genetic algorithm invoked after every K rounds of trading to evolve rules

    • Mutation (p=0.7)

    • Crossover

Sfi asm correction
SFI-ASM: Correction Corrections

  • Original had faulty mutation operator

    • Biased results to higher number of non-# bits

  • Correct solution for rules is to converge to all-# bits

    • Dividend and price too random to classify

  • With new operator, rules always converge

Sfi asm results
SFI-ASM: Results Corrections

  • Rules converge to all-# bits

    • Reach homogeneous rational expectation equilibrium eventually

  • With values for K < 100, complex trading emerges

    • Harder to persuade the model to do this with the new mutation operator

The repast framework and social simulations

Egb introduction
EGB: Introduction Modeling

  • Agent-based modeling has potential to avoid reification of actors

    • Reification: treating an abstract concept as concrete

  • Long-term simulations require “sociational endogenization” of actors

    • Actors must be internally dynamic

Egb background
EGB: Background Modeling

  • Essentialist perspective

    • Ignore change of actors

    • Fixed entities with attributes

  • Sociational perspective

    • Dynamic actors and relationships

    • Context-sensitive

Egb endogenization
EGB: Endogenization Modeling

  • Presents series of models to illustrate progression from reified actors to endogenous ones

    • Modeling emergence of state borders

  • Emergent Polarization (EP)

  • Democratic Peace (DP)

  • Nationalist Systems Change (NSC)

Egb emergent polarization
EGB: Emergent Polarization Modeling

  • Models conquest and expansion of states

  • Villages or counties on a finite 2d grid

  • States emerge as villages conquer neighbors

    • State has capital based on original village

    • Resources gathered from the territories depends on distance to capital

Egb ep turn structure
EGB: EP turn structure Modeling

  • Five phases per turn

    • Resource allocation

    • Decisions

    • Interaction

    • Resource updating

    • Structural change

The repast framework and social simulations

  • Resource allocation Modeling

    • Allocate troops to borders based on strength of neighbors

  • Decisions

    • Reciprocate aggressive action

    • Attempt unprovoked attacks

The repast framework and social simulations

  • Interaction Modeling

    • Resolve conflicts based on balance of power

  • Resource updating

    • States gain resources from provinces

  • Structural change

    • Structure of defeated state altered by outcome of conflicts

The repast framework and social simulations

  • Notes Modeling

    • States can spread too thin, inviting attack from other neighbors and opening multiple fronts to conflict

    • Can extend the model to allow alliances between states

Egb democratic peace
EGB: Democratic Peace Modeling

  • Adds categorical relationships to previous model

  • Observed that democracies do not fight each other

  • Add ‘democracy’ label to some states

  • Democracies do not fight each other, and form a defensive coalition

The repast framework and social simulations

  • Notes Modeling

    • Difference in balance of power produces significant results

    • Example of adding ‘categorical social’ processes

      • Threat evaluation is still relational

Egb nationalist systems change
EGB: Nationalist Systems Change Modeling

  • Introduce concept of actors separate from states : nations

    • Nations and states sometimes coincide, but not always

  • Each village has ‘cultural’ identity : string of trait values

  • Nation is a pattern string of traits with wildcards

The repast framework and social simulations

  • Nations founded and joined by agents Modeling

    • Capitals more likely to found nations due to resources

  • National identities have major impact on inter-state relations

    • ‘irredentist’ invasions to conquer conationals not under ‘home rule’

Egb conclusions
EGB: Conclusions Modeling

  • Agent-based simulations are better at modeling complex phenomenae than conventional approaches

  • Treating actors as themselves emergent and internally dynamic is necessary to good simulation over long time scales

Questions? Modeling