Exploring Complex Systems through Games and Computer Models

Santa Fe Institute – Project GUTS

http://www.projectguts.org

What is a complex system?

Complexdifficult-to-understand or difficult to predict

SystemA group of interacting, interrelated, or interdependent parts forming a whole.

So a “Complex System”is collections of simple units or agents interacting in a system. Large-scale behaviors of the system are difficult to understand or difficult to predict and may change, evolve, or adapt. (Also called Complex Adaptive Systems)

Climate change Loss of biodiversity Pollution Civil violenceSpread of disease

All of these issues are studied as “complex systems” using computer models.

Traffic jams Forest fire evacuation

These local problems can also be studied as complex systems:

Some problems we face

Scientists recreate complex systems in a "virtual world" on a computer where they are able to run many experiments without impacting the real world.

How do scientists study complex systems?

How do scientists study complex systems?

How do scientists study complex systems?

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The Computational Science Process

StarLogo is a tool used to create a Computational Model

Begin here

Creating Computer Models with StarLogo TNG

Create agents and environment Give agents and environment simple rules to follow No sophisticated mathematics or programming required Explore the behavior of complex systems

ThePredator,Prey, andGrassModel

Modeling and Computational Science

• A model is a representation of the interaction of real-world objects in a complex system.

• The goal is to gain an understanding of how the model’s results relate to real-world phenomena.

• Random factors built into the model and variables changed by the user cause different results to be generated when the model is run repeatedly.

Model Classification**

Idea ModelsIdea Models e.g. Model of Predator and Preye.g. Model of Predator and Prey

Minimal Models for SystemsMinimal Models for Systems e.g. Model of Wolves and Cariboue.g. Model of Wolves and Caribou

Systems ModelsSystems Models e.g. Model of every Wolf and e.g. Model of every Wolf and

Caribou in 5 square mile section Caribou in 5 square mile section of Yellowstoneof Yellowstone

*This classification scheme was proposed by J. Roughgarden.

Increasing complexity and detail Decreasing generality and applicability

Why wouldn’t you want to run these experiments in real-life?

What are Characteristics of Complex Adaptive Systems?

LLeaderless eaderless (aka decentralized)(aka decentralized)

Characteristics of Complex Adaptive Systems

A classic exampleBirds Flocking

A classic exampleflocking - Craig Reynolds

Separation: steer to avoid crowding local flockmates

Alignment: steer towards the average heading of local flockmates

Cohesion: steer to move toward the average position of local flockmates

http://www.red3d.com/cwr/boids/

EEmergent patterns mergent patterns develop from develop from the simple interactions of agentsthe simple interactions of agents

Characteristics of Complex Adaptive Systems

A classic exampleTermites

Termites model

NNon-linearon-linear The sum of the parts is The sum of the parts is not equal to the whole.not equal to the whole.

Characteristics of Complex Adaptive Systems

In Mathematics

NNon-linearon-linear means: f(a+b) means: f(a+b) f(a) f(a) + f(b)+ f(b)

Ex.) the exponential function is non-Ex.) the exponential function is non-linear. linear.

f(2 + 3) f(2 + 3) f(2) + f(3) f(2) + f(3)

f(5) f(5) f(2) + f(3) f(2) + f(3)

25 25 4 + 9 4 + 9 *Non-linear systems are systems that cannot be mathematically

described as the sum of their components.

SSelf-organizationelf-organization The system The system organizes itself.organizes itself.

Characteristics of Complex Adaptive Systems

A classic exampleSchelling Segregation Model

Developed by Thomas C. Schelling(Micromotives and Macrobehavior, 1978).

1.1. L Leaderless eaderless there is no leader there is no leader (boids)(boids)

2.2. E Emergent patterns mergent patterns develop from develop from the simple interactions of agents. the simple interactions of agents. (termites)(termites)

3.3. N Non-linearon-linear The sum of the parts The sum of the parts does not equal the whole. does not equal the whole.

4.4. S Self-organizationelf-organization The system The system organizes itselforganizes itself

4 Characteristics of Complex Adaptive Systems

Complex System or just Complicated?

Complex System or just Complicated?

Complex System or just Complicated?

Complex System or just Complicated?

Complex System or just Complicated?

Some examples of Complex Adaptive Systems

Global climate patternsGlobal climate patterns A termite moundA termite mound Highway traffic patternsHighway traffic patterns The spread of a disease in a The spread of a disease in a

populationpopulation The evolution of ideas in a The evolution of ideas in a

societysociety A food web in an ecosystemA food web in an ecosystem

The End