1. Management Information Systems
MIS 643
Agent-Based Modeling
and Simulation
2016/2017 Fall
Bertan Badur
Department of
Management Information Systems
Boğaziçi University

2. Outline
1. Introduction
2. Searching Mushrooms in a Forest

3. Introduction NetLogo User Manual Model Library
simple to install and experiment its model library
User Manual
Tutorials, Interface Guide and Programming Guide
Dictionary
Model Library
code examples

4. Agents Four kind of agents Moving agents – Turtles
Patches – square cells – space in world
Links – connect two turtles networks
Observer - controler of the model
create other agents
global variables
Each type of agents
commands
variables –
build-in such as color and location
user defined – additional
observer – gloabal variables

5. Global Variables Global variables: all agent can read and change
environment characteristics
model parameters

6. Primitives build-in procedure or command commands reporters E.g.:
tell agents something to do – return void
reporters
calculte and report something – return a value or list
E.g.:
mean - reports mean of a list of numbers
neighbors - reports list of surrounding patches

7. Context
each pice of code is “in the contxt of ” one kind or occationally more than one kind of agent
can be changed during execution
E.g.: ask turtles [move]

8. Accesing variables
agents – directly access variables for their own type
Exceptions:
observer varibles by all agents
turtles can access patchs variables they are currenlty on

9. Searching Mushrooms in a Forest
Is there a best strategy for searching mushrooms?
observation:
mushrooms in clusters
An intuitive strategy:
scanning an area in wide sweeps
upon finding a mushroom turning to smaller scale sweeps
as mushrroms in clusters

10. Searching Mushrooms in a Forest
What is large, small sweeps? and
How long to search in smaller sweeps?
Humans searching
pizzas, jobs, low prise goods, peace with neighbors

11. try different search strategies Purpose:
model of the problem
try different search strategies
Purpose:
what search strategy maximizes musrooms found in a given time
Ignore trees and vegitables, soil type
Musrooms are distributed as clusters
mushroom hunter
moving point
having a sensing radius
track of how many mushrooms found
how much time passed since last mushroom fouınd

12. clusters of items (mushrooms)
If the agent (hunter) finds an item
smaller-scale movement
If a critical time passes since last item found
switchs back to more streight movement
so as to find new clusters of items

13. Demonstrating Program: Mushroom Hunt
File/New
File/Save with extension “nlogo”
Settings
World geometry:
0,0 orgin, max-pxcor=16, max-pycor=16
33x33 squre latice
2 hunters – turtels
cluster of mushrooms – red patches
all other patches are black
setup – initialization
go – continuous operations

14. Create a button executing procedure setup
procedures – commands
to proc name
commands
end
Create a button executing procedure setup
Create a button executing procedure go
forever is cheked – forever button
write setup procedure
code tab

15. to setup
end
to go

16. to setup
ask patches [
set pcolor red ]
end
ask primitive asks selected agents to do actions by commands in brackets
set color of all pathces to red
set - primitive is assignment
pcolor – variable for patches

17. to setup
ask n-of 4 patches [
ask patches in-radius 5
set pcolor red ]
end
n-of: n-of number ageent set
in-radius : agents in-radius number

18. to setup
ask n-of 4 patches [
ask n-of 20 patches in-radius 5
set pcolor red ]
end
4 patches are randomly selected
for each randomly selected pathc
for all patches in radius 5
select 20 randomly
set their color to red

19. clear-all to setup clear-all ;abriviares as – ca - ask n-of 4 patches[
ask n-of 20 patches in-radius 5
set pcolor red ]
end
clear-all: clear all default values

20. using parameters globals [ num-clusters ] to setup clear-all
set num-clusters 4
ask n-of num-clusters patches
ask n-of 20 patches in-radius 5
set pcolor red
end

21. creating 2 hunters - turtles
create-tutrles 2 ;crt 2 [
set sıze 2
set color yellow ]
create 2 turtles
crt or create-tutles
build-in turtle variables:
size and color

22. go procedure to go ask turtles [search] end to search
ifelse tıme-sınce-last-found <= 20
[right (random 181) - 90]
[right (random 21) - 10]
forward 1
cifelse boolean condition
[ block whan true ]
[ block when false ]
right: turn right by angle in degrees

23. algorithm of move if timelast-found <= critical value
make a small turn
else
make a biger turn
if found – come on a red patch
set timelasf-fournd to 0
set color to yellow
increment timelast-found by one

24. variable for turtles tutrles-own [ tıme-sınce-last-found ]
variable for all turtles
time passed since last mushroom has found by the hunter

25. tıme-sınce-last-found initial value
crt 2 [
set sıze 2
set color yellow
set tıme-sınce-last-found 999 ]
initialze
tıme-sınce-last-found
to a very high value greater then 20

26. add to the search procedure
ifelse pcolor = red [
set tıme-sınce-last-found 0
set pcolor yellow ]
set tıme-sınce-last-found tıme-sınce-last-found + 1
end
if found pcolor is red
set tıme-sınce-last-found to 0
else
increment tıme-sınce-last-found by one

27. command center select turtles write commands hatch 1 [right 160]
show count turtles

28. further modifications
adding ticks
add reset-ticks
to the end of setup
add tick to the begining of go
following motion of hunters
add pen-down to the setup procedute when initilizing turtles