Programming for Swarm
CS655 Course Project
Weilin Zhong
Swarm Computing Models


The developments in micro-fabrication and nanotechnology
will enable the inexpensive manufacturing of massive
numbers of tiny computing elements
It will become possible to build new computing models,
which incorporate large numbers of small computing
elements
April 24 2001
CS655 Project Weilin Zhong
Swarm Computing Examples



Intelligent and responsive environment
Multi-agent system
Amorphous computing medium
April 24 2001
CS655 Project Weilin Zhong
Swarm Computing Models
System characteristics:
 Myriad numbers of elements.

Decentralized control.

Autonomous members behave with simple rules based on local
information, interacting with neighbors within a small radius.

Members collaborate to achieve sophisticated global behaviors.

Unreliable elements with limited power and resource connected in
irregular way.
Challenge to traditional programming models.

How to achieve complex global behaviors from locally information and
interaction without individually programming each member?

System must be adaptive and self-organized.
April 24 2001
CS655 Project Weilin Zhong
Learn From the Nature

Social Insects

Nest Building
Wasp Nets

Ant Forage
April 24 2001
CS655 Project Weilin Zhong
What Can We Learn?
Swarm Intelligence lies on its interaction network
 Direct Interaction
 A member interacts with its neighbors

Indirection Interaction

A member interacts indirectly with other members by
changing the common environment they live.
April 24 2001
CS655 Project Weilin Zhong
Programming for Swarm


StarLogo
GPL – Growing Point Language
April 24 2001
CS655 Project Weilin Zhong
StarLogo

StarLogo






A Programming language and environment of decentralized multi-agent
systems.
StarLogo System consists of Turtles and Patches
Turtles are the moving agents
Patches compose the environment where the turtles live
Turtles can change the state of the patches they visit
All turtles and patches are running in parallel
April 24 2001
CS655 Project Weilin Zhong
StarLogo

Data Type
Booleans(true, false), Lists, Numbers, and Strings.

Variable

Building-in State Variables of turtles and patches
Xcor, ycor,color,heading,breed,shown?, pendown?

Global Variables
turtles own [variables]
patches own [variables]

Local Variables
Let [:j 0]

Procedure
to procedure-name
List of Commands ; no separator needed
output something ; exits and returns something
end
April 24 2001
CS655 Project Weilin Zhong
StarLogo

Control Flow





if , ifelse,
case
loop, every, repeat, do [list of commands] forever
ignore
Primitives

Turtle Commands
forward, bk, die

Patch Commands
diffuse, diffuse4, nsum, nsum4

Observer Commands
ca, crt, setc, setpc
ask-turtles, ask-patches,
April 24 2001
CS655 Project Weilin Zhong
StarLogo
Ant Forage Model
 Observe Procedures
Setup the nest, foods,
generate ants
Initial ants and patches

Turtle Procedures
Look-for-food, find-food,
return-to-nest, find-nest

Patches Procedures
diffuse, evaporate
April 24 2001
CS655 Project Weilin Zhong
StarLogo
Ant Forage Model
April 24 2001
CS655 Project Weilin Zhong
StarLogo

Advantage



Limitations



Programmable Modeling Environment for Decentralized Multi-agent
System with Massive Parallel support
Suitable for biology life simulation, traffic, economic and ecology
models
Patches are regular coordinated spatial lattice
Patches have limited computational capabilities and weak influence
to its neighborhood
Problems with the language



Limited number of Data Types
Parameters only passed by value
No patches command center
April 24 2001
CS655 Project Weilin Zhong
Growing Point Language

Amorphous Computing Medium


GPL(Growing Point Language)


is a system of irregularly placed, identically programmed,
asynchronous, locally interacting computational particles
is a language to program amorphous computing medium to generate
highly complex and prespecified patterns
A CMOS Circuit layout

obtained from a small program encoding about 17 computational
states
April 24 2001
CS655 Project Weilin Zhong
Growing Point Language

Botanical Metaphor - Growing Points and Tropisms





Growing Point is a lotus of activity which can propagate its activities
to its neighbors
A growing point move according to its tropism, which is specified in
terms of differences in pheromone levels in its neighborhood
A growing point can “deposit” material and “secrete” pheromone
when it visits a particle
The path of growing point is the collection of particles it have visited,
expressing by the materials it has deposited on those particles.
Theorem

Amorphous media can be programmed to draw any prespecified
planar graph
April 24 2001
CS655 Project Weilin Zhong
Growing Point Language

Primitive Datatypes

Materials




Pheromone



markers to indicate where growing points have previously visited
can be associated with a color
can be sensed by a growing points to make growth decision
exists to guide the movement of growing point
radially symmetric about the source and monotonic decreasing in the
distance from the source
Tropism Expressions
April 24 2001
CS655 Project Weilin Zhong
GPL – A-to-B segment
(define-growing-point (A-to-B)
(material A-material)
(size 0)
(tropism (ortho+ B-pheromone))
(for-each-step
(when ((sensing? B-material)
(terminate))
(default
(propagate)))))
(define-growing-point (B-point)
(material B-material)
(size 0)
(for-each-step
(secrete+ 10 B-pheromone)))
(color
((B-material) "red")
((A-material) "yellow"))
(with-locations
(a b)
(at a (start-growing-point A-to-B))
(at b (start-growing-point B-point)))
April 24 2001
CS655 Project Weilin Zhong
GPL – A-to-B Segment
April 24 2001
CS655 Project Weilin Zhong
GPL

Advantages






Irregular and coordinate free domain
Strict locality
Identically Programmed member
Particles compose the environment
Suitable for responsive environment and improved
materials
Facilitate the analysis of programs
April 24 2001
CS655 Project Weilin Zhong
GPL -- Limitations and Improvement
Dynamic Problem
 Limitation
Static Particles
 Static Materials and Pheromone
 Static Model
---- lack of emergence, can only generated prespecified patterns


Improvement



Mobile particles
Changeable Material labeling and Pheromone Evaporation Model
Dynamic and Real-time Model
April 24 2001
CS655 Project Weilin Zhong
GPL – Limitation and Improvement

Reliability Issues



Extremely Friendly Environment
Reliable Communication System
Problems and Solutions



Communication Error
– Error recoverable encoding, retransmission
Unreliable Particles
– Neighborhood backups
Malicious Particles
-- Redundant Computation and agreement in neighborhood
April 24 2001
CS655 Project Weilin Zhong
StarLogo and GPL
Similarity




Decentralized system consisting large number of members
Autonomous members achieve complex global behaviors
from local interaction
Massive Parallel Model
Object Oriented
Shortcomings


No consideration of security and survivability
Performance
April 24 2001
CS655 Project Weilin Zhong
StarLogo and GPL

StarLogo





Multi-agent System
Mobile agents and static
env
Regularly discrete and
coordinated spatial
system
Dynamic and adaptive
models
April 24 2001
GPL




Amorphous Computing
Medium
Static particles
Irregular coordinated free
domain
Static Models
CS655 Project Weilin Zhong
Summary