Distributed Scheduling in Supply Chain Management

1
Distributed Scheduling in Supply Chain Management

• Emrah Zarifoglu
• 97021730

2
Decomposition

• Scheduling - very difficult, easily becomes
  NP-hard
• Decomposition is a good method
• Decomposing the problem into smaller manageable
  pieces
• Most popular decomposition method
• Distributed Scheduling

3
Distributed Scheduling

• A new approach for the local decision makers make
  their own schedules according to their local
  objectives and constraints regarding the overall
  objectives and constraints of the whole system

4
Characteristics of the Distribued Scheduling

• Decision makers agents
• entities having the properties of autonomy to
  operate without human intervention, social
  ability to communicate with others,
  pro-activeness to take an initiative role and
  reactivity to respond to changes in the
  environment

5
Agents

• Local agents
• Local decision making
• Regular agents
• Global agents
• Global decision making
• Manager agent, mediator agent or master agent
• Provide coordination
• Enter global database
• Initialize bidding process, select bids
• Resolve conflicts among local agents

6
Coordination between Agents

• Direct coordination or coordination via global
  agent
• Realization of coordination negotiation and
  bidding
• Simple bidding example
• Incoming job broadcasts bid request via global
  agent
• Eligible local agents give bids
• Global agent selects the best bid

7
Coordination between Agents (Contd)

• Bids may be dynamically revised (iterative
  bidding process)
• Collaboration between agents cooperation to
  achieve better global objectives
• Depending on architecture and communication in
  the system agents may have authority on others
  hierarchically

8
Information Flow in the System

• Centralized (hierarchical) systems
• A unique master scheduler makes the schedule in
  the system and the local controllers implement it
• Single layer centralized or multi-layer
  centralized
• Decentralized (heterarchical) systems

9
Advantages of Decentralized Systems

• Centralized
• If global scheduler fails ? system fails
• A fault in a point in hierarchy affects upstream
  and downstream
• Dictating all the duty

• Decentralized
• More fault tolerant ? reactive scheduling
• Shortened flow path ? decreased risk of failure
  and more robust schedules
• More initiative to local authorities (for human
  based systems) ? motivation for the job

10
Disadvantages of Decentralized Systems

• Centralized
• Less investment for education and technology
• Not much data sharing
• Unique responsible ? easier fault detection
• Better for global objective
• Simple systems

• Decentralized
• Giving more initiative to local agents ? more
  investment for education and technology
• Awareness of local agents about the system ? very
  good databases and information sharing systems
  (ERP, etc...)
• Distributed authority ? conflict at
  jurisdiction
• Does not guarantee global objectivity
• Hardware and software not well developed yet,
  congestion and deadlock in data transfer (huge
  traffic)

11
Classification of Decentralized Sytems

• Pure heterarchical systems
• No hierarchy
• Many times a feasible solution is enough
• Quasi-heterarchical systems
• Between pure heterarchical and hierarchical
• Single layer quasi-heterarchical and multi-layer
  quasi-heterarchical

12
Architectural Issues

• As number of layers increas ? more tendency of a
  change of decision given by lower level
  authorities by higher levels (if global objective
  is dominant)
• This may not be possible always due to bad flow
  of information

13
Communication Issues

• Existence of alternative agents ? bidding
  mechanism is more important
• If global objectives important ? cooperation is
  better
• Otherwise ? negotiation is better

14
Distributed Scheduling in Supply Chain

• Internet-based supply webs
• Bid request of customers from vendors
• Willing vendors bids
• Vendor with best offer is awarded via Internet
• Settings
• One customer multiple suppliers
• Multiple customers one supplier
• Multiple customers one supplier
• Multiple customers - multiple suppliers
• Not much study in the literature for
  Internet-based supply chains

15
Algorithm SC-JI

• One or a few customers multiple suppliers
• Job initiated
• Customer gives orders
• Orders are ranked by manager agent
• Bid request of manager agent from the vendors
  (local agents)
• Bid prepared by vendors
• Best bid selected by manager agent

16
Algorithm SC-VI

• Multiple customers - multiple vendors
• Vendor initiated
• Schedulable orders and vendors are grouped and
  linked to each other
• Vendors are ranked according to their expertise
• Starting by the most expert vendor, jobs are
  selected by vendors
• Manager agent is a conflict resolver
• After each cycle, same procedure is repeated if
  there are still unassigned orders
• Same procedure is held for all groups

17
Critics about Algorithms

• Incoming job may be represented as an agent
  associated with a customer
• For Algorithm SC-JI ? illeteracy of manager agent
  about underlying bidding process is a
  disadvantage
• For Algorithm SC-VI ? instead of grouping the
  teams and items we may let all teams and jobs to
  be available to each other
• Game theoretic approach may be very suitable for
  the nature of these algorithms

18
Conclusion

• Distributed Scheduling gives flexibility for
  problem solving
• Opportunities for new developments by the means
  of algorithms, cultural perception and education
• Distributed Scheduling may be applied to a
  variety of systems
• Promising area for the researchers