pm all rights reserved (tsang et al) bt’s collaborator problem regions engineers jobs p...

P MAll rights reserved (Tsang et al)

BT’s Collaborator ProblemRegions

Engineers

Jobs

P

Controllers

Tim

e

Job

Dur

atio

n /

Eng

inee

r A

vaila

bilit

yManager

Research Agenda:

To define for management a mechanism to achieve all-win solutions


Flexible Workforce Scheduling

for

Staff-empowerment

Edward Tsang, Qingfu Zhang, Wudong Liuand Tim Gosling

Botond Virginas, Chris Voudouris and G Owusu

All rights reserved; no part of this presentation should be copied or distributed without prior consent by the authors


The RECONNET Model

Manager

SellersBuyers

Solve

Req

uest

,

Contro

l Coe

ffici

ents Solution R

eports

Invitation to bids

Bids

Contract RetractionOffers / Acceptance / Reject / Wait

(Example)

M

Impl

emen

tatio

nR

esul

ts

Offers / rejects (binding)

Accept / Reject Offers (binding)

Multi-objectiveoptimisation


RECONNET Buyers

Region

Buyer = Controller ElementFor Completing Jobs

Job = {Start Time, Duration,Skill Required, Position,Value}

Reports

Control Information

Revenue, Distance,Preference & IncompletionCoefficients

Job Complete /Incomplete,Distance, Preference


RECONNET Sellers

Region

Seller = Controller Element ForAssigning Engineers

Engineer = {Position, Availability, Skill Preference}

Reports

Control Information

Assignment, Distance,Redundancy, Load Balancing

Contracts:Job,Distance, Preference, EngineerEngineers:Usage

Availability = Times Engineer AvailableSkill Preference = Skills in preference order


Manager: Multi-objective Optimisation

Manager

SellersBuyersInteract to

form contracts

Repeat

Control CoefficientsBuyer: Distance, Preference,

Revenue & IncompletionSeller: Assignments, Distance,

Redundancy, Load Balancing

Solution ReportsJobs: Completion, Distance & PreferenceContracts: Distance, Preference, EngineerEngineers: Total and available time

Look after company interests


Building Pareto Set of solutionsW

eig

ht

sf- va

lues

Ru

n

1

W 1

,1

w 1,

2

w 1,

3f 1

,1

f 1

,2

f1

f2R

un

2

W 2

,1

w 2,

2

w 2,

3f 2

,1

f 2

,2

Ru

n

3W 3

,1

w 3,

2

w 3,

3f 3

,1

f 3

,2

Ru

n

4

W 4

,1

w 4,

2

w 4,

3f 4

,1

f 4

,2

Ru

n

5

W 5

,1

w 5,

2

w 5,

3f 5

,1

f 5

,2

• Given quality metric for Pareto sets• Attempt to learn mapping from variable space to fitness space


Communication System Details• Problem solved over multiple rounds

• One round consists of four phases– Phase 1: Buyer to Buyer (Retraction Requests)– Phase 2: Buyer to Seller (Option requests, offers and

rejections)– Phase 3: Seller to Buyer (Options, Offer Accept, Option

Retract/Reject)– Phase 4: Buyer to Buyer (Retraction Accept, Reject &

Wait)

• System synchronises on the end of each round to keep everyone in step & prevent unfair advantage

Comms System 2


Communication System

Dete

rmin

esC

ontrol P

aram

eters

Manager

Buyer

Seller

Control

Para

meters

Start

Solving

Retract

Requests

Option

R

equests,O

ption O

ffers,O

ption R

ejects Option

s (includ

ingR

etraction

based options), O

ptionA

ccepts, Option

Retracts

(rejects)

Retract

Accepts,

Retract

Rejects,

Retract W

aits

End

D

etected

Report

Request

Report

sR

eports

Phase 1 Phase 2 Phase 3 Phase 4

Round 1 Round nSolution

StartSolution

End

Four C

omm

unication Phase in E

ach Round A

s Rou

nd 1

Retraction Example


Implementation• Use of Weblogic for communication

– JMS

• Use of Java for solution implementation

• Distributed implementation

• File based configuration and HTML/spreadsheet friendly output

• Flexible architecture allows easy expansion and modification


Contract Retraction Mechanism• Allows Hill-Climbing to find better solutions

– Without it solutions are ‘one shot’

Buyer 1 Buyer 2

Seller

Possible Chain of contract release ….

Seller

(2) Bids that requires Contract-release ($20)

(3) Binding request for contract release, with a compensation offer ($60)

(4) Accept contract-release

(4) Release contract

(1) Request for bids

Unserved job ($100)


General Results• The system is able to generate solutions to

‘real’ sized problems in about 5 minutes

• The system’s hill climbing mechanism allows initial solutions to be improved upon

• Managers are able to effect the solutions discovered by Buyer and Sellers


Management Power

• Force reduction in distance at Buyers

• Force reduction in preference at Buyers

• Force reduction in distance at Sellers

• Different Buyer configurations


Hill Climbing Demonstrated

• Use of retraction based options for improvement

Demonstration 3

UnfulfilledFree


Related Work


Related Work• Contract Net Protocol – no backtracking

– Smith 1980, IEEE Trans Computers

• Decommitting among cooperative Agents– Sen & Durfee 1994, 96, 98

• Contingency Contract – Based on future events, Raiffa, 1982

• Leveled Commitment Protocol – Sandholm & Lesser 2001, 02

• Two-phased negotiation– Price change between phases only, Akinee 2004


Leveled Commitment Protocol• Self-interested agents

• Decommission by penalties– Computed before contracts become binding

• Difficult to determine in a dynamic situation

• Could find global optimal– Through systematically search

• Intractable for BT’s problem with up to 105 jobs

• Nash equilibrium can be derived– Assuming perfect information

• Not true in many real life problems


Conclusions• Scheduling+Management problem

– Motivated by BT’s application– Multi-objectives optimisation

• Invented protocol for distributed hill climbing– Incorporating release & pricing mechanism– General protocol, could be used to implement different

HC strategies, such as GLS, Tabu Search

• This is a practical solution:– Management control– Local ownership– Found solutions to real sized problem in 5 mins

C


Questions


Future Expansion• Buyer: Contract Ordering and Selection

– When is a retraction option the better risk?– Conflict detection and offer delay

• Seller: Contract Generation and Pruning– When to issue retraction options or not– Is there a place for multiple retraction based options?– Should all contracts be priced?

• Seller: Contraction Offer acceptance– Should we consider delays to acceptance?– How do we bundle acceptances?

• Managers– How best to control solution formation in the Pareto set– How to present options to users


Distributed v CentralisedCentralised

• Advantages– Strong central control– Standardisation– No comms cost in

solution finding

• Disadvantages– Little local ownership– High comms cost in

dynamic environments

Distributed• Advantages

– Local ownership– Reduced scheduling

time– Divide and conquer– Natural to problem

• Disadvantages – Difficult to manage– Difficult to enforce

standards– Comms overhead


Mechanism Design

• Nobel Prize in Economics 2007

• For having laid the foundations of mechanism design theory

Leonid Hurwicz

Minnesotab.1917

Eric S Maskin

Princetonb.1950

Roger B MyersonChicagob.1951

pm all rights reserved (tsang et al) bt’s collaborator problem regions engineers jobs p...

Documents