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Introduction to Computing for Complex Systems
(Lab Session 2)
Daniel Martin KatzMichigan State University
College of Law
The Complete Code for the
Forest Fire model
The Forest Fire Model
the setup procedure
1st Operation is to Clear Everything
(a) The World Consists of Turtles and Patches
(c) Default is Now “square”
(b) Turtle Can Assume lots of Shapes
(d) What is the plain english version of this line of code?
(e) set-default-shapefor turtlesto “square”
(a) Call on Our Patches Using “Ask Patches”
(b) But Only A Certain Random Set of Patches
look at the brackets, what do these brackets do?
we need to learn these primitives:ask patchesrandom-float
The Ask Primitive
Random-Float
(a) Call on Our Patches Using “Ask Patches”
(b) But Only A Certain Random Set of Patches
(c) Patches With < “Density”
(d) Set Patch Color Green
With What Criteria?pxcor = min-pxcor[Notice The Brackets]
Again it is the “ask” “patches with”
(a) Again it is the “Ask” “Patches With”
(b) pxcor = min-pxcor
(c) To IngniteHere is where pxcor = min-pxcor(i.e. Where Pxcor =0)
How Does It Know What “Ignite” Means?
With What Criteria?pxcor = min-pxcor[Notice The Brackets]
To Do What?Ignite
Consult Netlogo Dictionary?Is it there?
Here is How (We Will Return to This in a Few)
Lets Look at the Set Command
variable= initial-trees
value= count patches with[patchcolor =green]
set variable value
variable= burned-trees
set variable value
value= numeric value of 0
notice how within ‘setup’ these globals are ultimately
assigned a value
Modular Code:
notice how the [ ignite ]
procedures are defined below
“sprout-fires 1” ?
[ set color red]note: color versus pcolorthis implies turtle not patch(see dictionary for distinction)fire turtle is set to red
“sprout-fires 1”sprouting of a turtle from breed = fires and a 1 per patch
set pcolor blacksetting patch color to black
set burned-trees to burned-trees +1
Modular Code:
now notice how [fade-embers]
procedures are defined below
[ set color color - 0.3] makes the red darker
“ask embers”embers are a breed
if color < red - 3.5‘If’ is a conditional
(balance of the command is triggered if condition is met)
Allows a slow fading of embersWhat does color < red - 3.5 imply?
[ set color color - 0.3] makes the red darker
“ask embers”embers are a breed
[set pcolor color die]
if color < red - 3.5‘If’ is a conditional
(balance of the command is triggered if condition is met)
Allows a slow fading of embersWhat does color < red - 3.5 imply?
We will focus upon the ‘to go’
procedure in the next class
3-D perspective on the model as it runs
notice how these turtles on the terrain
Exploration of the Forest Fire Model
(1) Modify the Color of the Forest to Blue
(2) Make the Fire Move North to South Instead of West to East
Modify the Color of the Forest to Blue
What Elements of the Code Do We Modify?
The Forest Fire Model
Procedures
The Forest Fire Model
Procedures
Make the Fire Move North to South Instead of West to East
Make the Fire Move North to South Instead of West to East
What Elements of the Code Do We Modify?
The Forest Fire Model
Procedures
The Forest Fire Model
Procedures
Try this Instead:
What is a Dependancy?
In Class Exercise: Identify Dependancies
in Fire Model
Why Does It Matter?
How Can We Represent Those Dependancies in Our Code?
Lets Discuss the Results
Mapping of the Code
In what sense is this model random?
In what sense is this model deterministic?
Thinking conceptually about the model procedures
all of these models involve a mixture of determinism and randomness
In what sense is this model random?
Thinking conceptually about the model procedures
Placement of the patches
subject to the selected density level
Watch the Model in 3D
Watch the Model in 3D
Watch the Model in 3D
Watch the Model in 3D
Watch the Model in 3D
In what sense is this model deterministic?
Thinking conceptually about the model procedures
The fire is really for G.U.I. purposes
result is basically already determined before the fire spreads
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