Method BACP

examples/bacp.cpp:119–175

Actual model

  /// Actual model
  BACP(const SizeOptions& opt)
    : IntMinimizeScript(opt), curr(curriculum[opt.size()]) {
    std::map<std::string, int> courseMap; // Map names to course numbers
    int maxCredit = 0;
    int numberOfCourses = 0;
    for (const Course* co=curr.courses; co->name != 0; co++) {
      courseMap[co->name] = numberOfCourses++;
      maxCredit += co->credit;
    }

    int p = curr.p;
    int a = curr.a;
    int b = curr.b;
    int c = curr.c;
    int d = curr.d;

    l = IntVarArray(*this, p, a, b);
    u = IntVar(*this, 0, maxCredit);
    q = IntVarArray(*this, p, c, d);
    x = IntVarArray(*this, numberOfCourses, 0, p-1);

    for (int j=0; j<p; j++) {
      BoolVarArgs xij(*this, numberOfCourses, 0, 1);
      IntArgs t(numberOfCourses);
      for (int i=0; i<numberOfCourses; i++) {
        rel(*this, (x[i]==j) == xij[i]);
        t[i] = curr.courses[i].credit;
      }
      // sum over all t*(xi==j) is load of period i
      linear(*this, t, xij, IRT_EQ, l[j]);
      // sum over all (xi==j) is number of courses in period i
      linear(*this, xij, IRT_EQ, q[j]);
    }

    // Precedence
    for (const char** prereq = curr.prereqs; *prereq != 0; prereq+=2)
      rel(*this, x[courseMap[*prereq]] < x[courseMap[*(prereq+1)]]);

    // Optimization criterion: minimize u
    max(*this, l, u);

    // Redundant constraints
    linear(*this, l, IRT_EQ, maxCredit);
    linear(*this, q, IRT_EQ, numberOfCourses);

    switch (opt.branching()) {
    case BRANCHING_NAIVE:
      branch(*this, x, INT_VAR_SIZE_MIN(), INT_VAL_MIN());
      break;
    case BRANCHING_LOAD:
      branch(*this, x, INT_VAR_SIZE_MIN(), INT_VAL(&load));
      break;
    case BRANCHING_LOAD_REV:
      branch(*this, x, INT_VAR_SIZE_MIN(), INT_VAL(&load_rev));
      break;
    }
  }
  /// Value selection function for load branching