may 9-11, 2004swarmfest, cscs, university of michigan 1 jesevol pietro terna [email protected]...

May 9-11, 2004 SwarmFest, CSCS, University of Michigan

1

jES

evol

Pietro Terna [email protected]

Department of Economics and Finance “G.Prato”

University of Torino - Italy

Evolving a simulated system of enterprises with jESevol and Swarm

web.econ.unito.it/terna

web.econ.unito.it/terna/jes


2

_jE

S->

jES

let a

nd jE

Sev

ol _______________________________________

jES jESlet and jESevol

_______________________________________


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From jES …

jVE

->jE

S

java Enterprise Simulator

… to jESlet (with a didactic goal) and …

… to jESevol, to simulate an evolving system of enterprises


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_ove

rvie

w

_______________________________________

Overview

_______________________________________


5

over

view

1

Overview 1/2

From jES (our java Enterprise Simulator), we have derived jESevol, or “Evolutionary java Enterprise Simulator”. jES is a large Swarm-based package[1] aimed at building simulation models both of actual enterprises and of virtual ones. jESevol simulates systems of enterprises or production units in an evolutionary context, where new ones arise continuously and some of the old are dropped out.

Our environment is a social space with metaphorical distances representing trustiness and cooperation among production units (the social capital). The production is represented by a sequence of orders; each order contains a recipe, i.e. the description of the sequence of activities to be done by several units to complete a specific production.

[1] Download last versions of jES, jESlet and jESevol from

http://web.econ.unito.it/terna/jes


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over

view

2

Overview 2/2

Two units can cooperate in the production process only if they are mutually visible in our social network. Units that do not receive a sufficient quantity of orders, as well as the ones that cannot send the accomplished orders to successive units, disappear.

New enterprises arise, in the attempt of filling the structural holes (Burt, 1992; Walker et al., 1997) of our social network.

A complex structure emerges from our environment, with a difficult and instable equilibrium whenever the social capital is not sufficient.

References

Burt R.S. (1992), Structural Holes – The Social Structure of Competition. Cambridge, MA, Harvard University Press.

Walker G., Kogut B., Shan W. (1997), Social Capital, Structural Holes and the Formation of an Industry Network, in Organization Science. Vol. 8, No. 2, pp.109-25.


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evol

ving

sys

tem

We look at an incomplete production system continuously adapting itself to the reality coming from the global demand of the market …

… while new firms arise and old ones are dropped off

To produce goods, supply chains are created and modified, according to the changes in exiting firms


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_jE

S b

asic

s

_______________________________________

jES basics

_______________________________________


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WD

, D

W, W

DW

WD side or formalism: What to Do

DW side or formalism: which is Doing What

WDW formalism: When Doing What

Three formalisms


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dict

iona

ry

unit = a productive structure; a unit is able to perform one of the steps required to accomplish an order

order = the object representing a good to be produced; an order contains technical information (the recipe describing the production steps)

recipe = a sequence of steps to be executed to produce a good

A dictionary


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_A f

lexi

ble

sche

me

_______________________________________

A flexible scheme in jESevol

_______________________________________


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DW

: a f

lexi

ble

sche

me

Units …

DW

… on a

toroidal space

(left and right borders and top and bottom ones are close together)

2

13

2

1

4

53

1

Each unit is able to

do a specific step …


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WD

: rec

ipes

WD

with the recipes of the orders (what to do) expressed as sequences of numbers; orders with recipes are randomly generated with different lengths and structures

1 3 2 4

5 3

4 3 5 1 1

…

… of a recipe


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mov

ing

reci

pes

DW and WD

2

13

2

1

4

53

11 3 2 4

1 3 2 4

moving around

among units

1 3 2 4

1 3 2 4 ?

lack of

visibilit

y

how to choose

Visibility is a metaphorical representation of trustiness and cooperation in a social network; when global visibility increases, we have more “social capital”


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visi

bili

ty a

nd …

visibility changes

new units appear randomly (enterprise creation)

• with strategic relationships …

• … or alone

some units are dropped out

Visibility increases with the time (initial visibility is randomly chosen)


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… b

ars

The left (blue) bar of each unit reports the number of waiting orders (do be done)

The down bar of each unit reports the number of consecutive clock ticks in which the unit has been idle

If > maxInactivity the unit is dropped out and all unsent products are lost

The right (red) bar of each unit reports the number of unsent products, due to the fact that a unit able to do the required step does not exist or is not visible

If > maxUnsentProducts the unit is dropped out and all unsent and waiting products are lost


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_an

intr

oduc

tory

cas

e

_______________________________________

An introductory case, robust and fragile

_______________________________________


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the

para

met

ers,

rob

ust i

ntro

duct

ory

case

potentialUnitTypes 5

unitGenerationInitialP 1

potentialUnitNumberPerType 2

newUnitGenerationP 0.0

interVisibilityMinLevel 0

increasingVisibilityStep 0.0

maxInactivity 10

maxUnsentProducts 10

max n. of types and max presence per type, here 5 * 2 with p=1

p of a new unit in each cycle, with a random type

in this basic case all units are visible and visibility does not change

we assume that an actual firm is dropped out from the market after three months of inactivity, so 10 ticks = 3 months of history

similarly …

Why 10? Our recipes have here maxStepNumber =5 and maxStepLength=2; potentially, in 10 ticks, each unit can receive an order, but only as a limit case; with this parameters the system can be exposed to a complete crash

Introductory robust case


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intr

oduc

tory

cas

e: r

obus

t cas

e

1,000 ticks = 25 years of actual time

only 5 units kept alive

global/potential

PRODUCTION

final/potential

final/global

Introductory robust case


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the

para

met

ers,

fra

gile

intr

oduc

tory

cas

e


unitGenerationInitialP 1




increasingVisibilityStep 0.0

maxInactivity 10


Our recipes have here

maxStepNumber 10 and

maxStepLength 1

Introductory fragile case

max n. of types and max presence per type, here 10 * 1 with p=1


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intr

oduc

tory

cas

e: f

ragi

le c

ase

150 ticks < 4 years of actual time

no units kept alive

global/potential

PRODUCTION

final/potential

final/global

Basic fragile case


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_a s

tudy

cas

e

__________________________________________________

A study case, with 3 versions:

(i) basic,

(ii) increasing social capital,

(iii) with greater financial intervention of the banking system

__________________________________________________


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the

para

met

ers,

bas

ic s

tudy

cas

e


unitGenerationInitialP 0.8




increasingVisibilityStep 5

maxInactivity 10


max n. of types and max presence per type, here 5 * 2 with p=0.8


in this study case, min visibility is 1, i.e. at least one common patch; visibility increases of 5 patches in each tick

(i) basic study case, starter file 5 in jESevol 0.3.00


maxStepNumber 5 and

maxStepLength 2


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stud

y ca

se: b

asic


a relevant variability in the number of units (social costs), with the trace of a cycle

global/potential

PRODUCTION

final/potential

final/global

(i) basic study case, starter file 5 in jESevol 0.3.00

a medium performance in term of potential production

some form of structure seems to emerge


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the

para

met

ers,

incr

easi

ng s

ocia

l cap

ital

st

udy

case







maxInactivity 10


max n. of types and max presence per type, here 5 * 2 with p=0.8


in this study case, min visibility is 1, i.e. at least one common patch; visibility increases of 10 patches in each tick

(ii) Increasing social capital study case, starter file 5.2 in jESevol 0.3.00


maxStepNumber 5 and

maxStepLength 2


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stud

y ca

se: i

ncre

asin

g so

cial

ca

pita

l


a relevant variability in the number of units (social costs), but now with an evident cycle

global/potential

PRODUCTION

final/potential

final/global

a good (and increasing) performance in term of potential production

evident structures emerge

(ii) Increasing social capital study case, starter file 5.2 in jESevol 0.3.00


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the

para

met

ers,

ban

k sy

stem

stu

dy c

ase







maxInactivity 15


in this study case, min visibility is 1, i.e. at least one common patch; visibility is increases of 5 patches in each tick

(iii) Greater financial intervention of the banking system study case, starter file 5.3 in jESevol 0.3.00


maxStepNumber 5 and

maxStepLength 2

we assume that an actual firm is dropped out from the market after 15 ticks of inactivity, instead of 10


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stud

y ca

se: b

ank

syst

em s

tudy

ca

se


a less relevant variability in the number of units (reduced social cost)s, always with an evident cycle

global/potential

PRODUCTION

final/potential

final/global

a good performance in term of potential production

evident structures emerge

(iii) Greater financial intervention of the banking system study case, starter file 5.3 in jESevol 0.3.00


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Sta

bili

ty; p

ersp

ecti

ves

Stability

Cases i, ii and iii are stable also running them for 4,000 ticks (one century)!

Short term enhancements

A lot of investigation is necessary on cases (i), (ii) and (iii) modelling explicitly the banking system, with the concurrent effects of the cases of bankruptcy in firms and banks

Using a Genetic Algorithm tool to choose units to be created at each tick and where to place them; the fitness will be generated by jESevol itself, from different points of view: the whole economic system, a specific unit, a cluster of units, …


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addr

ess

agai

n

[email protected]

web.econ.unito.it/terna

web.econ.unito.it/terna/jes

Let run case 5.2 or 5.3 at the question time!

may 9-11, 2004swarmfest, cscs, university of michigan 1 jesevol pietro terna [email protected]...

Documents

university of michigan

jes jeslet

production units

jes basics

itternajes slide

social capital

versions of jes

social network