gtsam/gtsam_unstable/discrete/Scheduler.h

/*
 * Scheduler.h
 * @brief an example how inference can be used for scheduling qualifiers
 * @date Mar 26, 2011
 * @author Frank Dellaert
 */

#pragma once

#include <gtsam_unstable/discrete/CSP.h>

namespace gtsam {

  /**
   * Scheduler class
   * Creates one variable for each student, and three variables for each
   * of the student's areas, for a total of 4*nrStudents variables.
   * The "student" variable will determine when the student takes the qual.
   * The "area" variables determine which faculty are on his/her committee.
   */
  class GTSAM_UNSTABLE_EXPORT Scheduler : public CSP {

  private:

    /** Internal data structure for students */
    struct Student {
      std::string name_;
      DiscreteKey key_; // key for student
      std::vector<DiscreteKey> keys_; // key for areas
      std::vector<std::string> areaName_;
      std::vector<double> advisor_;
      Student(size_t nrFaculty, size_t advisorIndex) :
        keys_(3), areaName_(3), advisor_(nrFaculty, 1.0) {
        advisor_[advisorIndex] = 0.0;
      }
      void print() const {
        using std::cout;
        cout << name_ << ": ";
        for (size_t area = 0; area < 3; area++)
          cout << areaName_[area] << " ";
        cout << std::endl;
      }
    };

    /** Maximum number of students */
    size_t maxNrStudents_;

    /** discrete keys, indexed by student and area index */
    std::vector<Student> students_;

    /** faculty identifiers */
    std::map<std::string, size_t> facultyIndex_;
    std::vector<std::string> facultyName_, slotName_, areaName_;

    /** area constraints */
    typedef std::map<std::string, std::vector<double> > FacultyInArea;
    FacultyInArea facultyInArea_;

    /** nrTimeSlots * nrFaculty availability constraints */
    std::string available_;

    /** which slots are good */
    std::vector<double> slotsAvailable_;

  public:

    /**
     * Constructor
     * WE need to know the number of students in advance for ordering keys.
     * then add faculty, slots, areas, availability, students, in that order
     */
    Scheduler(size_t maxNrStudents):maxNrStudents_(maxNrStudents) {
    }

    void addFaculty(const std::string& facultyName) {
      facultyIndex_[facultyName] = nrFaculty();
      facultyName_.push_back(facultyName);
    }

    size_t nrFaculty() const {
      return facultyName_.size();
    }

    /** boolean std::string of nrTimeSlots * nrFaculty */
    void setAvailability(const std::string& available) {
      available_ = available;
    }

    void addSlot(const std::string& slotName) {
      slotName_.push_back(slotName);
    }

    size_t nrTimeSlots() const {
      return slotName_.size();
    }

    const std::string& slotName(size_t s) const {
      return slotName_[s];
    }

    /** slots available, boolean */
    void setSlotsAvailable(const std::vector<double>& slotsAvailable) {
      slotsAvailable_ = slotsAvailable;
    }

    void addArea(const std::string& facultyName, const std::string& areaName) {
      areaName_.push_back(areaName);
      std::vector<double>& table = facultyInArea_[areaName]; // will create if needed
      if (table.empty()) table.resize(nrFaculty(), 0);
      table[facultyIndex_[facultyName]] = 1;
    }

    /**
     * Constructor that reads in faculty, slots, availibility.
     * Still need to add areas and students after this
     */
    Scheduler(size_t maxNrStudents, const std::string& filename);

    /** get key for student and area, 0 is time slot itself */
    const DiscreteKey& key(size_t s, boost::optional<size_t> area = boost::none) const;

    /** addStudent has to be called after adding slots and faculty */
    void addStudent(const std::string& studentName, const std::string& area1,
        const std::string& area2, const std::string& area3,
        const std::string& advisor);

    /// current number of students
    size_t nrStudents() const {
      return students_.size();
    }

    const std::string& studentName(size_t i) const;
    const DiscreteKey& studentKey(size_t i) const;
    const std::string& studentArea(size_t i, size_t area) const;

    /** Add student-specific constraints to the graph */
    void addStudentSpecificConstraints(size_t i, boost::optional<size_t> slot = boost::none);

    /** Main routine that builds factor graph */
    void buildGraph(size_t mutexBound = 7);

    /** print */
    void print(const std::string& s = "Scheduler") const;

    /** Print readable form of assignment */
    void printAssignment(sharedValues assignment) const;

    /** Special print for single-student case */
    void printSpecial(sharedValues assignment) const;

    /** Accumulate faculty stats */
    void accumulateStats(sharedValues assignment,
        std::vector<size_t>& stats) const;

    /** Eliminate, return a Bayes net */
    DiscreteBayesNet::shared_ptr eliminate() const;

    /** Find the best total assignment - can be expensive */
    sharedValues optimalAssignment() const;

    /** find the assignment of students to slots with most possible committees */
    sharedValues bestSchedule() const;

    /** find the corresponding most desirable committee assignment */
    sharedValues bestAssignment(sharedValues bestSchedule) const;

  }; // Scheduler

} // gtsam