LP simplification abstract base class.Instances of classes derived from SPxSimplifier may be loaded to SoPlex in order to simplify LPs before solving them. SoPlex will call simplify() on itself. Generally any SPxLP can be given to a SPxSimplifier for simplify()ing it. The simplification cannot be undone, but given an primal/dual solution for the simplified SPxLP, the simplifier can reconstruct the primal/dual solution of the unsimplified LP. More...

#include <spxsimplifier.h>

Public Member Functions
Access / modfication
virtual const char *	getName () const
	get name of simplifier. More...

virtual Real	timeUsed () const

Simplifying / unsimplifying
virtual Result	simplify (SPxLP &lp, Real eps, Real delta)=0
	simplify SPxLP `lp` with identical primal and dual feasibility tolerance. More...

virtual Result	simplify (SPxLP &lp, Real eps, Real feastol, Real opttol, bool keepbounds=false)=0
	simplify SPxLP `lp` with independent primal and dual feasibility tolerance. More...

virtual void	unsimplify (const Vector &, const Vector &, const Vector &, const Vector &, const SPxSolver::VarStatus[], const SPxSolver::VarStatus[], bool isOptimal=true)=0
	reconstructs an optimal solution for the unsimplified LP. More...

virtual Result	result () const =0
	returns result status of the simplification More...

virtual bool	isUnsimplified () const
	specifies whether an optimal solution has already been unsimplified. More...

virtual const Vector &	unsimplifiedPrimal ()=0
	returns a reference to the unsimplified primal solution. More...

virtual const Vector &	unsimplifiedDual ()=0
	returns a reference to the unsimplified dual solution. More...

virtual const Vector &	unsimplifiedSlacks ()=0
	returns a reference to the unsimplified slack values. More...

virtual const Vector &	unsimplifiedRedCost ()=0
	returns a reference to the unsimplified reduced costs. More...

virtual SPxSolver::VarStatus	getBasisRowStatus (int) const =0
	gets basis status for a single row. More...

virtual SPxSolver::VarStatus	getBasisColStatus (int) const =0
	gets basis status for a single column. More...

virtual void	getBasis (SPxSolver::VarStatus[], SPxSolver::VarStatus[], const int rowsSize=-1, const int colsSize=-1) const =0
	get optimal basis. More...

virtual Real	getObjoffset () const
	get objective offset. More...

virtual void	addObjoffset (const Real val)
	add objective offset. More...

virtual void	setMinReduction (const Real minRed)
	set minimal reduction threshold to continue simplification More...

Consistency check
virtual bool	isConsistent () const
	consistency check More...

Protected Attributes
Protected Data
const char *	m_name
	name of the simplifier More...

Timer *	m_timeUsed
	user time used for simplification More...

Timer::TYPE	m_timerType

int	m_remRows
	number of removed rows More...

int	m_remCols
	number of removed columns More...

int	m_remNzos
	number of removed nonzero coefficients More...

int	m_chgBnds
	number of changed bounds More...

int	m_chgLRhs
	number of change right-hand sides More...

int	m_keptBnds
	number of kept bounds More...

int	m_keptLRhs
	number of kept left- and right-hand sides More...

Real	m_objoffset
	objective offset More...

Real	m_minReduction
	minimal reduction (sum of removed rows/cols) to continue simplification More...

SPxOut *	spxout
	message handler More...

Types
enum	Result { OKAY = 0, INFEASIBLE = 1, DUAL_INFEASIBLE = 2, UNBOUNDED = 3, VANISHED = 4 }
	Result of the simplification. More...

	SPxSimplifier (const char *p_name, Timer::TYPE ttype=Timer::USER_TIME)
	constructor More...

	SPxSimplifier (const SPxSimplifier &old)
	copy constructor More...

SPxSimplifier &	operator= (const SPxSimplifier &rhs)
	assignment operator More...

virtual	~SPxSimplifier ()
	destructor. More...

virtual SPxSimplifier *	clone () const =0
	clone function for polymorphism More...

Detailed Description

LP simplification abstract base class.

Instances of classes derived from SPxSimplifier may be loaded to SoPlex in order to simplify LPs before solving them. SoPlex will call simplify() on itself. Generally any SPxLP can be given to a SPxSimplifier for simplify()ing it. The simplification cannot be undone, but given an primal/dual solution for the simplified SPxLP, the simplifier can reconstruct the primal/dual solution of the unsimplified LP.

Definition at line 41 of file spxsimplifier.h.

Member Enumeration Documentation

◆ Result

enum Result

Result of the simplification.

Enumerator
OKAY	simplification could be done
INFEASIBLE	primal infeasibility was detected
DUAL_INFEASIBLE	dual infeasibility was detected
UNBOUNDED	primal unboundedness was detected
VANISHED	the problem was so much simplified that it vanished

Definition at line 81 of file spxsimplifier.h.

Constructor & Destructor Documentation

◆ SPxSimplifier() [1/2]

SPxSimplifier	(	const char *	p_name,
		Timer::TYPE	ttype = `Timer::USER_TIME`
	)

explicit

constructor

Definition at line 95 of file spxsimplifier.h.

References TimerFactory::createTimer(), and SPxSimplifier::isConsistent().

◆ SPxSimplifier() [2/2]

SPxSimplifier ( const SPxSimplifier & old )

copy constructor

Definition at line 115 of file spxsimplifier.h.

References TimerFactory::createTimer(), and SPxSimplifier::isConsistent().

◆ ~SPxSimplifier()

virtual ~SPxSimplifier ( )

virtual

destructor.

Definition at line 157 of file spxsimplifier.h.

References SPxSimplifier::clone(), soplex::spx_free(), and Timer::~Timer().

Member Function Documentation

◆ addObjoffset()

virtual void addObjoffset ( const Real val )

virtual

add objective offset.

Definition at line 228 of file spxsimplifier.h.

Referenced by SPxMainSM::aggregateVars(), SPxMainSM::FixVariablePS::FixVariablePS(), SPxMainSM::FreeColSingletonPS::FreeColSingletonPS(), and SPxMainSM::MultiAggregationPS::MultiAggregationPS().

◆ clone()

virtual SPxSimplifier* clone ( ) const

pure virtual

clone function for polymorphism

Implemented in SPxMainSM.

Referenced by SPxSimplifier::~SPxSimplifier().

◆ getBasis()

virtual void getBasis	(	SPxSolver::VarStatus	[],
		SPxSolver::VarStatus	[],
		const int	rowsSize = `-1`,
		const int	colsSize = `-1`
	)		const

pure virtual

get optimal basis.

Implemented in SPxMainSM.

Referenced by SoPlex::_decompResolveWithoutPreprocessing(), SoPlex::_resolveWithoutPreprocessing(), SoPlex::_solveRealForRational(), SoPlex::_storeSolutionReal(), SoPlex::_storeSolutionRealFromPresol(), and SPxSimplifier::isUnsimplified().

◆ getBasisColStatus()

virtual SPxSolver::VarStatus getBasisColStatus ( int ) const

pure virtual

gets basis status for a single column.

Implemented in SPxMainSM.

Referenced by SPxSimplifier::isUnsimplified().

◆ getBasisRowStatus()

virtual SPxSolver::VarStatus getBasisRowStatus ( int ) const

pure virtual

gets basis status for a single row.

Implemented in SPxMainSM.

Referenced by SPxSimplifier::isUnsimplified().

◆ getName()

virtual const char* getName ( ) const

virtual

get name of simplifier.

Definition at line 171 of file spxsimplifier.h.

References SPxSimplifier::m_name.

Referenced by SoPlex::getSimplifierName().

◆ getObjoffset()

virtual Real getObjoffset ( ) const

virtual

get objective offset.

Definition at line 222 of file spxsimplifier.h.

References SPxSimplifier::m_objoffset.

Referenced by SoPlex::_decompSimplifyAndSolve(), and SoPlex::_preprocessAndSolveReal().

◆ isConsistent()

virtual bool isConsistent ( ) const

virtual

consistency check

Definition at line 245 of file spxsimplifier.h.

References soplex::operator<<().

Referenced by SPxSimplifier::operator=(), and SPxSimplifier::SPxSimplifier().

◆ isUnsimplified()

virtual bool isUnsimplified ( ) const

virtual

specifies whether an optimal solution has already been unsimplified.

Reimplemented in SPxMainSM.

Definition at line 195 of file spxsimplifier.h.

References SPxSimplifier::getBasis(), SPxSimplifier::getBasisColStatus(), SPxSimplifier::getBasisRowStatus(), SPxSimplifier::unsimplifiedDual(), SPxSimplifier::unsimplifiedPrimal(), SPxSimplifier::unsimplifiedRedCost(), and SPxSimplifier::unsimplifiedSlacks().

Referenced by SoPlex::_decompResolveWithoutPreprocessing(), SoPlex::_resolveWithoutPreprocessing(), SoPlex::_solveRealForRational(), SoPlex::_storeSolutionReal(), and SoPlex::_storeSolutionRealFromPresol().

◆ operator=()

SPxSimplifier& operator= ( const SPxSimplifier & rhs )

assignment operator

Definition at line 133 of file spxsimplifier.h.

References SPxSimplifier::isConsistent(), SPxSimplifier::m_chgBnds, SPxSimplifier::m_chgLRhs, SPxSimplifier::m_keptBnds, SPxSimplifier::m_keptLRhs, SPxSimplifier::m_minReduction, SPxSimplifier::m_name, SPxSimplifier::m_objoffset, SPxSimplifier::m_remCols, SPxSimplifier::m_remNzos, SPxSimplifier::m_remRows, SPxSimplifier::m_timerType, SPxSimplifier::m_timeUsed, and SPxSimplifier::spxout.

Referenced by SPxMainSM::operator=().

◆ result()

virtual Result result ( ) const

pure virtual

returns result status of the simplification

Implemented in SPxMainSM.

Referenced by SoPlex::_storeSolutionReal(), SoPlex::_storeSolutionRealFromPresol(), and SPxSimplifier::timeUsed().

◆ setMinReduction()

virtual void setMinReduction ( const Real minRed )

virtual

set minimal reduction threshold to continue simplification

Definition at line 234 of file spxsimplifier.h.

Referenced by SoPlex::_enableSimplifierAndScaler().

◆ simplify() [1/2]

virtual Result simplify	(	SPxLP &	lp,
		Real	eps,
		Real	delta
	)

pure virtual

simplify SPxLP lp with identical primal and dual feasibility tolerance.

Implemented in SPxMainSM.

Referenced by SoPlex::_decompSimplifyAndSolve(), SoPlex::_preprocessAndSolveReal(), SoPlex::_solveRealForRational(), and SPxSimplifier::timeUsed().

◆ simplify() [2/2]

virtual Result simplify	(	SPxLP &	lp,
		Real	eps,
		Real	feastol,
		Real	opttol,
		bool	keepbounds = `false`
	)

pure virtual

simplify SPxLP lp with independent primal and dual feasibility tolerance.

Implemented in SPxMainSM.

◆ timeUsed()

virtual Real timeUsed ( ) const

virtual

Definition at line 175 of file spxsimplifier.h.

References SPxSimplifier::result(), SPxSimplifier::simplify(), Timer::time(), and SPxSimplifier::unsimplify().

◆ unsimplifiedDual()

virtual const Vector& unsimplifiedDual ( )

pure virtual

returns a reference to the unsimplified dual solution.

Implemented in SPxMainSM.

Referenced by SoPlex::_solveRealForRational(), SoPlex::_storeSolutionReal(), SoPlex::_storeSolutionRealFromPresol(), and SPxSimplifier::isUnsimplified().

◆ unsimplifiedPrimal()

virtual const Vector& unsimplifiedPrimal ( )

pure virtual

returns a reference to the unsimplified primal solution.

Implemented in SPxMainSM.

Referenced by SoPlex::_solveRealForRational(), SoPlex::_storeSolutionReal(), SoPlex::_storeSolutionRealFromPresol(), and SPxSimplifier::isUnsimplified().

◆ unsimplifiedRedCost()

virtual const Vector& unsimplifiedRedCost ( )

pure virtual

returns a reference to the unsimplified reduced costs.

Implemented in SPxMainSM.

Referenced by SoPlex::_storeSolutionReal(), SoPlex::_storeSolutionRealFromPresol(), and SPxSimplifier::isUnsimplified().

◆ unsimplifiedSlacks()

virtual const Vector& unsimplifiedSlacks ( )

pure virtual

returns a reference to the unsimplified slack values.

Implemented in SPxMainSM.

Referenced by SoPlex::_storeSolutionReal(), SoPlex::_storeSolutionRealFromPresol(), and SPxSimplifier::isUnsimplified().

◆ unsimplify()

virtual void unsimplify	(	const Vector &	,
		const Vector &	,
		const Vector &	,
		const Vector &	,
		const SPxSolver::VarStatus	[],
		const SPxSolver::VarStatus	[],
		bool	isOptimal = `true`
	)

pure virtual

reconstructs an optimal solution for the unsimplified LP.

Implemented in SPxMainSM.

Referenced by SoPlex::_decompResolveWithoutPreprocessing(), SoPlex::_resolveWithoutPreprocessing(), SoPlex::_solveRealForRational(), SoPlex::_storeSolutionReal(), SoPlex::_storeSolutionRealFromPresol(), and SPxSimplifier::timeUsed().

Member Data Documentation

◆ m_chgBnds

int m_chgBnds

protected

number of changed bounds

Definition at line 60 of file spxsimplifier.h.

Referenced by SPxMainSM::aggregateVars(), SPxMainSM::handleExtremes(), SPxSimplifier::operator=(), SPxMainSM::simplify(), SPxMainSM::simplifyCols(), and SPxMainSM::simplifyRows().

◆ m_chgLRhs

int m_chgLRhs

protected

number of change right-hand sides

Definition at line 62 of file spxsimplifier.h.

Referenced by SPxMainSM::aggregateVars(), SPxMainSM::handleExtremes(), SPxSimplifier::operator=(), SPxMainSM::simplify(), and SPxMainSM::simplifyRows().

◆ m_keptBnds

int m_keptBnds

protected

number of kept bounds

Definition at line 64 of file spxsimplifier.h.

Referenced by SPxSimplifier::operator=(), SPxMainSM::simplify(), and SPxMainSM::simplifyRows().

◆ m_keptLRhs

int m_keptLRhs

protected

number of kept left- and right-hand sides

Definition at line 66 of file spxsimplifier.h.

Referenced by SPxSimplifier::operator=(), SPxMainSM::simplify(), and SPxMainSM::simplifyRows().

◆ m_minReduction

Real m_minReduction

protected

minimal reduction (sum of removed rows/cols) to continue simplification

Definition at line 70 of file spxsimplifier.h.

Referenced by SPxMainSM::duplicateCols(), SPxMainSM::duplicateRows(), SPxMainSM::multiaggregation(), SPxSimplifier::operator=(), SPxMainSM::simplifyCols(), SPxMainSM::simplifyDual(), and SPxMainSM::simplifyRows().

◆ m_name

const char* m_name

protected

name of the simplifier

Definition at line 49 of file spxsimplifier.h.

Referenced by SPxSimplifier::getName(), and SPxSimplifier::operator=().

◆ m_objoffset

Real m_objoffset

protected

objective offset

Definition at line 68 of file spxsimplifier.h.

Referenced by SPxSimplifier::getObjoffset(), SPxSimplifier::operator=(), SPxMainSM::propagatePseudoobj(), SPxMainSM::simplify(), and SPxMainSM::trivialHeuristic().

◆ m_remCols

int m_remCols

protected

number of removed columns

Definition at line 56 of file spxsimplifier.h.

Referenced by SPxMainSM::aggregateVars(), SPxMainSM::duplicateCols(), SPxMainSM::multiaggregation(), SPxSimplifier::operator=(), SPxMainSM::removeEmpty(), SPxMainSM::simplify(), SPxMainSM::simplifyCols(), and SPxMainSM::simplifyDual().

◆ m_remNzos

int m_remNzos

protected

number of removed nonzero coefficients

Definition at line 58 of file spxsimplifier.h.

Referenced by SPxMainSM::aggregateVars(), SPxMainSM::duplicateCols(), SPxMainSM::duplicateRows(), SPxMainSM::handleExtremes(), SPxMainSM::multiaggregation(), SPxSimplifier::operator=(), SPxMainSM::removeRowSingleton(), SPxMainSM::simplify(), SPxMainSM::simplifyCols(), SPxMainSM::simplifyDual(), and SPxMainSM::simplifyRows().

◆ m_remRows

int m_remRows

protected

number of removed rows

Definition at line 54 of file spxsimplifier.h.

Referenced by SPxMainSM::aggregateVars(), SPxMainSM::duplicateRows(), SPxMainSM::handleExtremes(), SPxMainSM::multiaggregation(), SPxSimplifier::operator=(), SPxMainSM::removeEmpty(), SPxMainSM::removeRowSingleton(), SPxMainSM::simplify(), SPxMainSM::simplifyCols(), SPxMainSM::simplifyDual(), and SPxMainSM::simplifyRows().

◆ m_timerType

Timer::TYPE m_timerType

protected

Definition at line 52 of file spxsimplifier.h.

Referenced by SPxSimplifier::operator=().

◆ m_timeUsed

Timer* m_timeUsed

protected

user time used for simplification

Definition at line 51 of file spxsimplifier.h.

Referenced by SPxSimplifier::operator=(), and SPxMainSM::simplify().

◆ spxout

SPxOut* spxout

protected

message handler

Definition at line 72 of file spxsimplifier.h.

Referenced by SPxMainSM::aggregateVars(), SPxMainSM::duplicateCols(), SPxMainSM::duplicateRows(), SPxMainSM::fixColumn(), SPxMainSM::handleExtremes(), SPxMainSM::multiaggregation(), SPxSimplifier::operator=(), SPxMainSM::removeEmpty(), SPxMainSM::removeRowSingleton(), SPxMainSM::simplify(), SPxMainSM::simplifyCols(), SPxMainSM::simplifyDual(), SPxMainSM::simplifyRows(), and SPxMainSM::unsimplify().

SoPlex

Public Member Functions

Protected Attributes

Types

Detailed Description

Member Enumeration Documentation

◆ Result

Constructor & Destructor Documentation

◆ SPxSimplifier() [1/2]

◆ SPxSimplifier() [2/2]

◆ ~SPxSimplifier()

Member Function Documentation

◆ addObjoffset()

◆ clone()

◆ getBasis()

◆ getBasisColStatus()

◆ getBasisRowStatus()

◆ getName()

◆ getObjoffset()

◆ isConsistent()

◆ isUnsimplified()

◆ operator=()

◆ result()

◆ setMinReduction()

◆ simplify() [1/2]

◆ simplify() [2/2]

◆ timeUsed()

◆ unsimplifiedDual()

◆ unsimplifiedPrimal()

◆ unsimplifiedRedCost()

◆ unsimplifiedSlacks()

◆ unsimplify()

Member Data Documentation

◆ m_chgBnds

◆ m_chgLRhs

◆ m_keptBnds

◆ m_keptLRhs

◆ m_minReduction

◆ m_name

◆ m_objoffset

◆ m_remCols

◆ m_remNzos

◆ m_remRows

◆ m_timerType

◆ m_timeUsed

◆ spxout