operations_research::sat::RoutingFullPathNeighborhoodGenerator Class Reference

#include <cp_model_lns.h>

Inheritance diagram for operations_research::sat::RoutingFullPathNeighborhoodGenerator:

Public Member Functions
	RoutingFullPathNeighborhoodGenerator (NeighborhoodGeneratorHelper const *helper, absl::string_view name)
Neighborhood	Generate (const CpSolverResponse &initial_solution, double difficulty, absl::BitGenRef random) final
Public Member Functions inherited from operations_research::sat::NeighborhoodGenerator
	NeighborhoodGenerator (absl::string_view name, NeighborhoodGeneratorHelper const *helper)
virtual	~NeighborhoodGenerator ()=default
virtual bool	ReadyToGenerate () const
	Returns true if the neighborhood generator can generate a neighborhood.
double	GetUCBScore (int64_t total_num_calls) const
void	AddSolveData (SolveData data)
double	Synchronize ()
std::string	name () const
	Returns a short description of the generator.
int64_t	num_calls () const
	Number of times this generator was called.
int64_t	num_fully_solved_calls () const
	Number of time the neighborhood was fully solved (OPTIMAL/INFEASIBLE).
int64_t	num_improving_calls () const
	Out of num_calls(), how many improved the given solution.
int64_t	num_consecutive_non_improving_calls () const
double	difficulty () const
	The current difficulty of this generator.
double	deterministic_limit () const
	The current time limit that the sub-solve should use on this generator.

Additional Inherited Members
Protected Attributes inherited from operations_research::sat::NeighborhoodGenerator
const std::string	name_
const NeighborhoodGeneratorHelper &	helper_
absl::Mutex	generator_mutex_

Detailed Description

This routing based LNS generator aims are relaxing one full path, and make some room on the other paths to absorb the nodes of the relaxed path.

In order to do so, it will relax the first and the last arc of each path in the circuit or routes constraints. Then it will relax all arc literals in one random path. Then it will relax random arcs in the remaining paths until it reaches the given difficulty.

Definition at line 767 of file cp_model_lns.h.

Constructor & Destructor Documentation

RoutingFullPathNeighborhoodGenerator()

operations_research::sat::RoutingFullPathNeighborhoodGenerator::RoutingFullPathNeighborhoodGenerator ( NeighborhoodGeneratorHelper const * helper, absl::string_view name )

inline

Definition at line 769 of file cp_model_lns.h.

Member Function Documentation

Generate()

Neighborhood operations_research::sat::RoutingFullPathNeighborhoodGenerator::Generate ( const CpSolverResponse & initial_solution, double difficulty, absl::BitGenRef random )

finalvirtual

Generates a "local" subproblem for the given seed.

The difficulty will be in [0, 1] and is related to the asked neighborhood size (and thus local problem difficulty). A difficulty of 0.0 means empty neighborhood and a difficulty of 1.0 means the full problem. The algorithm should try to generate a neighborhood according to this difficulty which will be dynamically adjusted depending on whether or not we can solve the subproblem in a given time limit.

The given initial_solution should contain a feasible solution to the initial CpModelProto given to this class. Any solution to the returned CPModelProto should also be valid solution to the same initial model.

This function should be thread-safe.

Remove a corner case where all paths are empty.

Collect all unique variables.

Select variables to relax.

Relax the start and end of each path to ease relocation.

Randomize paths.

Relax all variables (if possible) in one random path.

Relax more variables until the target is reached.

Remove variable and clean up empty paths.

Compute the set of variables to fix.

Implements operations_research::sat::NeighborhoodGenerator.

Definition at line 2244 of file cp_model_lns.cc.

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

• ortools/sat/cp_model_lns.h
• ortools/sat/cp_model_lns.cc