Lab Week 13: Stable Matchings

Announcements

• Two short quizzes posted this week
  • one on stacks
  • one on stable matchings
  • can be completed any time before end of classes
• Accountability group survey posted tomorrow

Today

1. Project Hints and Suggestions
2. Time to Work

Agent.java

Representation of an agent

• preferences stored in ArrayList<Agent> prefList
  • first element is most preferred Agent, etc
• current match stored as Agent curMatch
  • curMatch = null indicates agent is not matched
• curIndex is index of curMatch in prefList
  • initially curIndex = -1

Agent Instance Methods

• boolean prefers(Agent a, Agent b) returns true if this agent prefers a to b
  • all agents prefer being matched with prefList agent to not being matched (i.e., curMatch == null) to being matching with agent not in prefList
  • null parameter indicates not being matched

• void proposal(Agent a) this agent receives proposal from Agent a

• void refusal() this agent was refused by curMatch
  • if curMatch is last in prefList, unmatch and return
  • otherwise, set curMatch to next in prefList, and propose

SMInstance

• Stores:
  • ArrayList<Agent> hospitals
  • ArrayList<Agent> residents
• Matching is implicit in hospitals/residents
  • matching consists of pairs (r, h) where:
    1. h = r.curMatch
    2. r = h.curMatch
  • Matching a class for dealing with matchings
    • stores an ArrayList of Pair<Agent>s

SMInstance Methods

• void computeStableMatching() use the McVitie & Wilson algorithm to compute a stable matching
  • matching is implicit in state values of curMatch
  • hint: make sure each resident r sets curMatch before making first proposal
    • which method actually sets a proposer’s match?
• Matching getMatching() return a Matching consisting of pairs (r, h) where r = h.curMatch and h = r.curMatch
• void setMatching(Matching m)
• Pair<Agent> getBlockingPair()
• boolean isStable()

General Advice

• Start with Agent class
• Use AgentTester to test each method
• No method should require too much code
• Use print statements to help debug!