constraint_solver.h File Reference

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Classes
struct	DefaultPhaseParameters
	This struct holds all parameters for the default search. More...
class	Solver
	Solver Class. More...
struct	Solver::IntegerCastInfo
	Holds semantic information stating that the 'expression' has been cast into 'variable' using the Var() method, and that 'maintainer' is responsible for maintaining the equality between 'variable' and 'expression'. More...
struct	Solver::SearchLogParameters
	Creates a search monitor from logging parameters. More...
class	BaseObject
	A BaseObject is the root of all reversibly allocated objects. More...
class	PropagationBaseObject
	NOLINT. More...
class	Decision
	A Decision represents a choice point in the search tree. More...
class	DecisionVisitor
	A DecisionVisitor is used to inspect a decision. More...
class	DecisionBuilder
	A DecisionBuilder is responsible for creating the search tree. More...
class	ProfiledDecisionBuilder
class	Demon
	A Demon is the base element of a propagation queue. More...
class	ModelVisitor
	Model visitor. More...
class	Constraint
	A constraint is the main modeling object. More...
class	CastConstraint
	Cast constraints are special channeling constraints designed to keep a variable in sync with an expression. More...
class	SearchMonitor
	A search monitor is a simple set of callbacks to monitor all search events. More...
class	Rev< T >
	This class adds reversibility to a POD type. More...
class	NumericalRev< T >
	Subclass of Rev<T> which adds numerical operations. More...
class	RevArray< T >
	Reversible array of POD types. More...
class	NumericalRevArray< T >
	Subclass of RevArray<T> which adds numerical operations. More...
class	IntExpr
	The class IntExpr is the base of all integer expressions in constraint programming. More...
class	IntVarIterator
	The class Iterator has two direct subclasses. More...
class	InitAndGetValues
	Utility class to encapsulate an IntVarIterator and use it in a range-based loop. More...
struct	InitAndGetValues::Iterator
class	IntVar
	The class IntVar is a subset of IntExpr. More...
class	SolutionCollector
	This class is the root class of all solution collectors. More...
struct	SolutionCollector::SolutionData
class	OptimizeVar
	This class encapsulates an objective. More...
class	SearchLimit
	Base class of all search limits. More...
class	RegularLimit
	Usual limit based on wall_time, number of explored branches and number of failures in the search tree. More...
class	ImprovementSearchLimit
class	IntervalVar
	Interval variables are often used in scheduling. More...
class	SequenceVar
	A sequence variable is a variable whose domain is a set of possible orderings of the interval variables. More...
class	AssignmentElement
class	IntVarElement
class	IntervalVarElement
class	SequenceVarElement
	The SequenceVarElement stores a partial representation of ranked interval variables in the underlying sequence variable. More...
class	AssignmentContainer< V, E >
class	Assignment
	An Assignment is a variable -> domains mapping, used to report solutions to the user. More...
class	Pack
class	DisjunctiveConstraint
class	SolutionPool
	This class is used to manage a pool of solutions. More...

Namespaces
namespace	operations_research
	Collection of objects used to extend the Constraint Solver library.

Functions
	ABSL_DECLARE_FLAG (int64_t, cp_random_seed)
	Declaration of the core objects for the constraint solver. More...
int64_t	CpRandomSeed ()
std::ostream &	operator<< (std::ostream &out, const Solver *const s)
int64_t	Zero ()
	NOLINT. More...
int64_t	One ()
	This method returns 1. More...
std::ostream &	operator<< (std::ostream &out, const BaseObject *const o)
std::ostream &	operator<< (std::ostream &out, const Assignment &assignment)
void	SetAssignmentFromAssignment (Assignment *target_assignment, const std::vector< IntVar * > &target_vars, const Assignment *source_assignment, const std::vector< IntVar * > &source_vars)
	NOLINT. More...

Function Documentation

ABSL_DECLARE_FLAG()

ABSL_DECLARE_FLAG	(	int64_t	,
		cp_random_seed
	)

Declaration of the core objects for the constraint solver.

The literature around constraint programming is extremely dense but one can find some basic introductions in the following links:

• http://en.wikipedia.org/wiki/Constraint_programming
• http://kti.mff.cuni.cz/~bartak/constraints/index.html

Here is a very simple Constraint Programming problem:

If we see 56 legs and 20 heads, how many two-legged pheasants and four-legged rabbits are we looking at?

Here is some simple Constraint Programming code to find out:

void pheasant() { Solver s("pheasant"); // Create integer variables to represent the number of pheasants and // rabbits, with a minimum of 0 and a maximum of 20. IntVar* const p = s.MakeIntVar(0, 20, "pheasant")); IntVar* const r = s.MakeIntVar(0, 20, "rabbit")); // The number of heads is the sum of pheasants and rabbits. IntExpr* const heads = s.MakeSum(p, r); // The number of legs is the sum of pheasants * 2 and rabbits * 4. IntExpr* const legs = s.MakeSum(s.MakeProd(p, 2), s.MakeProd(r, 4)); // Constraints: the number of legs is 56 and heads is 20. Constraint* const ct_legs = s.MakeEquality(legs, 56); Constraint* const ct_heads = s.MakeEquality(heads, 20); s.AddConstraint(ct_legs); s.AddConstraint(ct_heads); DecisionBuilder* const db = s.MakePhase(p, r, Solver::CHOOSE_FIRST_UNBOUND, Solver::ASSIGN_MIN_VALUE); s.NewSearch(db); CHECK(s.NextSolution()); LOG(INFO) << "rabbits -> " << r->Value() << ", pheasants -> " << p->Value(); LOG(INFO) << s.DebugString(); s.EndSearch(); }

which outputs:

rabbits -> 8, pheasants -> 12 Solver(name = "pheasant", state = OUTSIDE_SEARCH, branches = 0, fails = 0, decisions = 0 propagation loops = 11, demons Run = 25, Run time = 0 ms)