operations_research::ImprovementSearchLimit Class Reference

#include <constraint_solver.h>

Inheritance diagram for operations_research::ImprovementSearchLimit:

Public Member Functions
	ImprovementSearchLimit (Solver *solver, IntVar *objective_var, bool maximize, double objective_scaling_factor, double objective_offset, double improvement_rate_coefficient, int improvement_rate_solutions_distance)
	--— Improvement Search Limit --—
	ImprovementSearchLimit (Solver *solver, std::vector< IntVar * > objective_vars, std::vector< bool > maximize, std::vector< double > objective_scaling_factors, std::vector< double > objective_offsets, double improvement_rate_coefficient, int improvement_rate_solutions_distance)
	~ImprovementSearchLimit () override
void	Copy (const SearchLimit *limit) override
SearchLimit *	MakeClone () const override
	Allocates a clone of the limit.
bool	CheckWithOffset (absl::Duration offset) override
bool	AtSolution () override
void	Init () override
	This method is called when the search limit is initialized.
void	Install () override
	A search monitors adds itself on the active search.
Public Member Functions inherited from operations_research::SearchLimit
	SearchLimit (Solver *const s)
	SearchLimit (const SearchLimit &)=delete
	This type is neither copyable nor movable.
SearchLimit &	operator= (const SearchLimit &)=delete
	~SearchLimit () override
	-------— Search Limits -------—
bool	crossed () const
	Returns true if the limit has been crossed.
bool	Check ()
void	EnterSearch () override
	Internal methods.
void	BeginNextDecision (DecisionBuilder *b) override
	Before calling DecisionBuilder::Next.
void	PeriodicCheck () override
	Periodic call to check limits in long running methods.
void	RefuteDecision (Decision *d) override
	Before refuting the decision.
std::string	DebugString () const override
void	Install () override
	A search monitors adds itself on the active search.
Public Member Functions inherited from operations_research::SearchMonitor
	SearchMonitor (Solver *const s)
	SearchMonitor (const SearchMonitor &)=delete
	This type is neither copyable nor movable.
SearchMonitor &	operator= (const SearchMonitor &)=delete
	~SearchMonitor () override
virtual void	RestartSearch ()
	Restart the search.
virtual void	ExitSearch ()
	End of the search.
virtual void	EndNextDecision (DecisionBuilder *b, Decision *d)
	After calling DecisionBuilder::Next, along with the returned decision.
virtual void	ApplyDecision (Decision *d)
	Before applying the decision.
virtual void	AfterDecision (Decision *d, bool apply)
virtual void	BeginFail ()
	Just when the failure occurs.
virtual void	EndFail ()
	After completing the backtrack.
virtual void	BeginInitialPropagation ()
	Before the initial propagation.
virtual void	EndInitialPropagation ()
	After the initial propagation.
virtual bool	AcceptSolution ()
virtual void	NoMoreSolutions ()
	When the search tree is finished.
virtual bool	LocalOptimum ()
virtual bool	AcceptDelta (Assignment *delta, Assignment *deltadelta)
virtual void	AcceptNeighbor ()
	After accepting a neighbor during local search.
virtual void	AcceptUncheckedNeighbor ()
	After accepting an unchecked neighbor during local search.
virtual bool	IsUncheckedSolutionLimitReached ()
virtual int	ProgressPercent ()
virtual void	Accept (ModelVisitor *visitor) const
	Accepts the given model visitor.
Solver *	solver () const
Public Member Functions inherited from operations_research::BaseObject
	BaseObject ()
	BaseObject (const BaseObject &)=delete
	This type is neither copyable nor movable.
BaseObject &	operator= (const BaseObject &)=delete
virtual	~BaseObject ()

Additional Inherited Members
Static Public Attributes inherited from operations_research::SearchMonitor
static constexpr int	kNoProgress = -1
Protected Member Functions inherited from operations_research::SearchMonitor
void	ListenToEvent (Solver::MonitorEvent event)

Detailed Description

Limit based on the improvement rate of 'objective_var' or a lexicographic objective composed of 'objective_vars'. This limit proceeds in two stages: 1) During the phase of the search in which the objective is strictly improving, a threshold value is computed as the minimum improvement rate of the objective, based on the 'improvement_rate_coefficient' and 'improvement_rate_solutions_distance' parameters. 2) Then, if the search continues beyond this phase of strict improvement, the limit stops the search when the improvement rate of the objective gets below this threshold value.

Definition at line 4738 of file constraint_solver.h.

Constructor & Destructor Documentation

ImprovementSearchLimit() [1/2]

operations_research::ImprovementSearchLimit::ImprovementSearchLimit	(	Solver *	solver,
		IntVar *	objective_var,
		bool	maximize,
		double	objective_scaling_factor,
		double	objective_offset,
		double	improvement_rate_coefficient,
		int	improvement_rate_solutions_distance )

--— Improvement Search Limit --—

Definition at line 4564 of file search.cc.

ImprovementSearchLimit() [2/2]

operations_research::ImprovementSearchLimit::ImprovementSearchLimit	(	Solver *	solver,
		std::vector< IntVar * >	objective_vars,
		std::vector< bool >	maximize,
		std::vector< double >	objective_scaling_factors,
		std::vector< double >	objective_offsets,
		double	improvement_rate_coefficient,
		int	improvement_rate_solutions_distance )

Definition at line 4576 of file search.cc.

~ImprovementSearchLimit()

operations_research::ImprovementSearchLimit::~ImprovementSearchLimit ( )

override

Definition at line 4595 of file search.cc.

Member Function Documentation

AtSolution()

bool operations_research::ImprovementSearchLimit::AtSolution ( )

overridevirtual

This method is called when a valid solution is found. If the return value is true, then search will resume after. If the result is false, then search will stop there.

To simplify, we'll consider minimization only in the rest of the code, which requires taking the opposite of the objective value if maximizing.

In case we haven't got enough solutions during the first stage, the limit never stops the search.

We need to have 'improvement_rate_solutions_distance_' + 1 element in the 'improvements_', so the distance between improvements is 'improvement_rate_solutions_distance_'.

Reimplemented from operations_research::SearchMonitor.

Definition at line 4670 of file search.cc.

CheckWithOffset()

bool operations_research::ImprovementSearchLimit::CheckWithOffset ( absl::Duration offset )

overridevirtual

Same as Check() but adds the 'offset' value to the current time when time is considered in the limit.

Implements operations_research::SearchLimit.

Definition at line 4636 of file search.cc.

Copy()

void operations_research::ImprovementSearchLimit::Copy ( const SearchLimit * limit )

overridevirtual

Copy a limit. Warning: leads to a direct (no check) downcasting of 'limit' so one needs to be sure both SearchLimits are of the same type.

Implements operations_research::SearchLimit.

Definition at line 4612 of file search.cc.

Init()

void operations_research::ImprovementSearchLimit::Init ( )

overridevirtual

This method is called when the search limit is initialized.

Implements operations_research::SearchLimit.

Definition at line 4602 of file search.cc.

Install()

void operations_research::ImprovementSearchLimit::Install ( )

overridevirtual

A search monitors adds itself on the active search.

Registers itself on the solver such that it gets notified of the search and propagation events. Override to incrementally install listeners for specific events.

Reimplemented from operations_research::SearchMonitor.

Definition at line 4597 of file search.cc.

MakeClone()

SearchLimit * operations_research::ImprovementSearchLimit::MakeClone ( ) const

overridevirtual

Allocates a clone of the limit.

Implements operations_research::SearchLimit.

Definition at line 4629 of file search.cc.

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The documentation for this class was generated from the following files:

• ortools/constraint_solver/constraint_solver.h
• ortools/constraint_solver/search.cc