operations_research::glop::Preprocessor Class Reference

Detailed Description

Preprocessor This is the base class for preprocessors.

Todo

(user): On most preprocessors, calling Run() more than once will not work as expected. Fix? or document and crash in debug if this happens.

Definition at line 48 of file preprocessor.h.

#include <preprocessor.h>

Inheritance diagram for operations_research::glop::Preprocessor:

Public Member Functions
	Preprocessor (const GlopParameters *parameters)
	Preprocessor (const Preprocessor &)=delete
Preprocessor &	operator= (const Preprocessor &)=delete
virtual	~Preprocessor ()
virtual bool	Run (LinearProgram *lp)=0
virtual void	RecoverSolution (ProblemSolution *solution) const =0
ProblemStatus	status () const
virtual void	UseInMipContext ()
void	SetTimeLimit (TimeLimit *time_limit)

Protected Member Functions
bool	IsSmallerWithinFeasibilityTolerance (Fractional a, Fractional b) const
bool	IsSmallerWithinPreprocessorZeroTolerance (Fractional a, Fractional b) const

Protected Attributes
ProblemStatus	status_
const GlopParameters &	parameters_
bool	in_mip_context_
std::unique_ptr< TimeLimit >	infinite_time_limit_
TimeLimit *	time_limit_

Constructor & Destructor Documentation

Preprocessor() [1/2]

operations_research::glop::Preprocessor::Preprocessor ( const GlopParameters * parameters )

explicit

Preprocessor

Definition at line 57 of file preprocessor.cc.

Preprocessor() [2/2]

operations_research::glop::Preprocessor::Preprocessor ( const Preprocessor & )

delete

~Preprocessor()

operations_research::glop::Preprocessor::~Preprocessor ( )

virtual

Definition at line 63 of file preprocessor.cc.

Member Function Documentation

IsSmallerWithinFeasibilityTolerance()

bool operations_research::glop::Preprocessor::IsSmallerWithinFeasibilityTolerance ( Fractional a, Fractional b ) const

inlineprotected

Returns true if a is less than b (or slighlty greater than b with a given tolerance).

Definition at line 85 of file preprocessor.h.

IsSmallerWithinPreprocessorZeroTolerance()

bool operations_research::glop::Preprocessor::IsSmallerWithinPreprocessorZeroTolerance ( Fractional a, Fractional b ) const

inlineprotected

Todo

(user): use an absolute tolerance here to be even more defensive?

Definition at line 89 of file preprocessor.h.

operator=()

Preprocessor & operations_research::glop::Preprocessor::operator= ( const Preprocessor & )

delete

RecoverSolution()

virtual void operations_research::glop::Preprocessor::RecoverSolution ( ProblemSolution * solution ) const

pure virtual

Stores the optimal solution of the linear program that was passed to Run(). The given solution needs to be set to the optimal solution of the linear program "modified" by Run().

Implemented in operations_research::glop::AddSlackVariablesPreprocessor, operations_research::glop::DoubletonEqualityRowPreprocessor, operations_research::glop::DoubletonFreeColumnPreprocessor, operations_research::glop::DualizerPreprocessor, operations_research::glop::EmptyColumnPreprocessor, operations_research::glop::EmptyConstraintPreprocessor, operations_research::glop::FixedVariablePreprocessor, operations_research::glop::ForcingAndImpliedFreeConstraintPreprocessor, operations_research::glop::FreeConstraintPreprocessor, operations_research::glop::ImpliedFreePreprocessor, operations_research::glop::MainLpPreprocessor, operations_research::glop::ProportionalColumnPreprocessor, operations_research::glop::ProportionalRowPreprocessor, operations_research::glop::ScalingPreprocessor, operations_research::glop::ShiftVariableBoundsPreprocessor, operations_research::glop::SingletonColumnSignPreprocessor, operations_research::glop::SingletonPreprocessor, operations_research::glop::ToMinimizationPreprocessor, and operations_research::glop::UnconstrainedVariablePreprocessor.

Run()

virtual bool operations_research::glop::Preprocessor::Run ( LinearProgram * lp )

pure virtual

Runs the preprocessor by modifying the given linear program. Returns true if a postsolve step will be needed (i.e. RecoverSolution() is not the identity function). Also updates status_ to something different from ProblemStatus::INIT if the problem was solved (including bad statuses like ProblemStatus::ABNORMAL, ProblemStatus::INFEASIBLE, etc.).

Implemented in operations_research::glop::AddSlackVariablesPreprocessor, operations_research::glop::DoubletonEqualityRowPreprocessor, operations_research::glop::DoubletonFreeColumnPreprocessor, operations_research::glop::DualizerPreprocessor, operations_research::glop::EmptyColumnPreprocessor, operations_research::glop::EmptyConstraintPreprocessor, operations_research::glop::FixedVariablePreprocessor, operations_research::glop::ForcingAndImpliedFreeConstraintPreprocessor, operations_research::glop::FreeConstraintPreprocessor, operations_research::glop::ImpliedFreePreprocessor, operations_research::glop::MainLpPreprocessor, operations_research::glop::ProportionalColumnPreprocessor, operations_research::glop::ProportionalRowPreprocessor, operations_research::glop::ScalingPreprocessor, operations_research::glop::ShiftVariableBoundsPreprocessor, operations_research::glop::SingletonColumnSignPreprocessor, operations_research::glop::SingletonPreprocessor, operations_research::glop::ToMinimizationPreprocessor, and operations_research::glop::UnconstrainedVariablePreprocessor.

SetTimeLimit()

void operations_research::glop::Preprocessor::SetTimeLimit ( TimeLimit * time_limit )

inline

Definition at line 80 of file preprocessor.h.

status()

ProblemStatus operations_research::glop::Preprocessor::status ( ) const

inline

Returns the status of the preprocessor. A status different from ProblemStatus::INIT means that the problem is solved and there is not need to call subsequent preprocessors.

Definition at line 70 of file preprocessor.h.

UseInMipContext()

virtual void operations_research::glop::Preprocessor::UseInMipContext ( )

inlinevirtual

Some preprocessors only need minimal changes when used with integer variables in a MIP context. Setting this to true allows to consider integer variables as integer in these preprocessors.

Not all preprocessors handle integer variables correctly, calling this function on them will cause a LOG(FATAL).

Reimplemented in operations_research::glop::DualizerPreprocessor, operations_research::glop::ProportionalColumnPreprocessor, and operations_research::glop::ScalingPreprocessor.

Definition at line 78 of file preprocessor.h.

Member Data Documentation

in_mip_context_

bool operations_research::glop::Preprocessor::in_mip_context_

protected

Definition at line 98 of file preprocessor.h.

infinite_time_limit_

std::unique_ptr<TimeLimit> operations_research::glop::Preprocessor::infinite_time_limit_

protected

Definition at line 99 of file preprocessor.h.

parameters_

const GlopParameters& operations_research::glop::Preprocessor::parameters_

protected

Definition at line 97 of file preprocessor.h.

status_

ProblemStatus operations_research::glop::Preprocessor::status_

protected

Definition at line 96 of file preprocessor.h.

time_limit_

TimeLimit* operations_research::glop::Preprocessor::time_limit_

protected

Definition at line 100 of file preprocessor.h.

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

• ortools/glop/preprocessor.h
• ortools/glop/preprocessor.cc