2 qlpsolve.hh -- declare Active_constraints, Inactive_iter
4 source file of the LilyPond music typesetter
6 (c) 1997 Han-Wen Nienhuys <hanwen@stack.nl>
17 This class represents the set of active (binding) constraints
18 which can be active while the QLP algorithm is in a feasible
19 point. The active constraints are numbered.
20 If the constraints are of the form
24 then the binding constraints are those where the >= is equality.
28 class Active_constraints {
29 friend class Inactive_iter;
34 Array<int> inactive; // actually this is a set, not an array.
35 Ineq_constrained_qp const *opt;
40 Vector vec(int k) const { return opt->cons[k]; }
41 Real rhs(int k) const { return opt->consrhs[k]; }
44 /** drop constraint. drop constraint k from the active set. k is the index of the
45 constraint in #active#
52 add constraint j to the active set j is the index of the
53 constraint in #inactive#
57 /// exchange in and out.
58 void exchange(int in, int out) { add(in); drop (out); }
61 Vector find_active_optimum(Vector g);
63 /// get lagrange multipliers.
64 Vector get_lagrange(Vector v);
66 Active_constraints(Ineq_constrained_qp const *op);
67 /** construct: no constraints active, n vars. Put the equalities
68 into the constraints. */
76 loop through the inactive constraints.
80 Active_constraints const* ac;
82 Inactive_iter(Active_constraints const &c) { ac=&c; j=0; }
83 int idx() const { return j; }
84 void operator ++(int) { j++; }
85 int constraint_id() const { return ac->inactive[j]; }
86 Vector vec() const { return ac->vec(constraint_id()); }
87 Real rhs() const { return ac->rhs(constraint_id()); }
88 bool ok() const { return j < ac->inactive.size(); }