Weighted start basis.Class SPxWeightST is an implementation of a SPxStarter for generating a Simplex starting basis. Using method setupWeights() it sets up arrays weight and coWeight, or equivalently rowWeight and colWeight. (rowWeight and colWeight are just pointers initialized to weight and coWeight according to the representation of SoPlex base passed to method generate().) More...

#include <spxweightst.h>

Inheritance diagram for SPxWeightST:

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Public Member Functions
Construction / destruction
	SPxWeightST ()
	default constructor.

	SPxWeightST (const SPxWeightST &old)
	copy constructor

SPxWeightST &	operator= (const SPxWeightST &rhs)
	assignment operator

virtual	~SPxWeightST ()
	destructor.

virtual SPxStarter *	clone () const
	clone function for polymorphism

Generation of a start basis
void	generate (SPxSolver &base)
	generates start basis for loaded basis.

Debugging
virtual bool	isConsistent () const
	consistency check.

Public Member Functions inherited from SPxStarter
virtual const char *	getName () const
	get name of starter.

	SPxStarter (const char *name)
	constructor

	SPxStarter (const SPxStarter &old)
	copy constructor

SPxStarter &	operator= (const SPxStarter &rhs)
	assignment operator

virtual	~SPxStarter ()
	destructor.

Protected Member Functions
Protected helpers
virtual void	setupWeights (SPxSolver &base)
	sets up variable weights.

Protected Attributes
Protected data
DataArray< Real >	rowWeight
	weight value for LP rows.

DataArray< Real >	colWeight
	weight value for LP columns.

DataArray< bool >	rowRight
	set variable to rhs?.

DataArray< bool >	colUp
	set primal variable to upper bound.

Protected Attributes inherited from SPxStarter
const char *	m_name
	name of the starter

Private Member Functions
Private helpers
void	setPrimalStatus (SPxBasis::Desc &, const SPxSolver &, const SPxId &)

Private Attributes
Private data
DataArray< int >	forbidden

DataArray< Real > *	weight

DataArray< Real > *	coWeight

Detailed Description

Weighted start basis.

Class SPxWeightST is an implementation of a SPxStarter for generating a Simplex starting basis. Using method setupWeights() it sets up arrays weight and coWeight, or equivalently rowWeight and colWeight. (rowWeight and colWeight are just pointers initialized to weight and coWeight according to the representation of SoPlex base passed to method generate().)

The weight values are then used to setup a starting basis for the LP: vectors with low values are likely to become dual (i.e. basic for a column basis) and such with high values are likely to become primal (i.e. nonbasic for a column basis).

However, if a variable having an upper and lower bound is to become primal, there is still a choice for setting it either to its upper or lower bound. Members rowRight and colUp are used to determine where to set a primal variable. If rowRight[i] is set to a nonzero value, the right-hand side inequality is set tightly for the i 'th to become primal. Analogously, If colUp[j] is nonzero, the j 'th variable will be set to its upper bound if it becomes primal.

Definition at line 56 of file spxweightst.h.

Constructor & Destructor Documentation

SPxWeightST ( )

default constructor.

Definition at line 110 of file spxweightst.h.

References SPxWeightST::isConsistent().

Referenced by SPxWeightST::clone().

SPxWeightST ( const SPxWeightST & old )

copy constructor

Definition at line 116 of file spxweightst.h.

References SPxWeightST::colWeight, SPxWeightST::coWeight, SPxWeightST::isConsistent(), SPxWeightST::rowWeight, and SPxWeightST::weight.

virtual ~SPxWeightST ( )

virtual

destructor.

Definition at line 170 of file spxweightst.h.

References SPxWeightST::coWeight, and SPxWeightST::weight.

Member Function Documentation

virtual SPxStarter* clone ( ) const

virtual

clone function for polymorphism

Implements SPxStarter.

Reimplemented in SPxVectorST, and SPxSumST.

Definition at line 176 of file spxweightst.h.

References SPxWeightST::SPxWeightST().

void generate ( SPxSolver & base )

virtual

generates start basis for loaded basis.

Implements SPxStarter.

Definition at line 215 of file spxweightst.cpp.

References SPxSolver::coDim(), SPxSolver::coId(), SPxBasis::Desc::colStatus(), SPxSolver::COLUMN, SPxWeightST::colUp, SPxWeightST::colWeight, SPxSolver::coVector(), SPxWeightST::coWeight, Vector::dim(), SPxSolver::dim(), EPS, SPxWeightST::forbidden, SVector::index(), soplex::infinity, SPxSolver::init(), soplex::initPrefs(), SPxSolver::loadBasis(), SPxLP::lower(), SVector::maxAbs(), SPxLP::maxObj(), MSG_DEBUG, SPxLP::nCols(), SPxLP::nRows(), SPxLP::number(), SPxBasis::Desc::P_ON_LOWER, SPxBasis::Desc::P_ON_UPPER, SPxSolver::pVec(), SPxSolver::rep(), DataArray< T >::reSize(), SPxId::ROW_ID, SPxWeightST::rowRight, SPxWeightST::rowWeight, soplex::setDualStatus(), SPxWeightST::setPrimalStatus(), SPxWeightST::setupWeights(), SVector::size(), DataArray< T >::size(), soplex::spxout, STABLE, SPxLP::upper(), SVector::value(), SPxSolver::vector(), and SPxWeightST::weight.

bool isConsistent ( ) const

virtual

consistency check.

Reimplemented from SPxStarter.

Definition at line 32 of file spxweightst.cpp.

References SPxWeightST::colUp, SPxWeightST::colWeight, DataArray< T >::isConsistent(), SPxWeightST::rowRight, and SPxWeightST::rowWeight.

Referenced by SPxSumST::operator=(), SPxVectorST::operator=(), SPxWeightST::operator=(), SPxSumST::SPxSumST(), SPxVectorST::SPxVectorST(), and SPxWeightST::SPxWeightST().

SPxWeightST& operator= ( const SPxWeightST & rhs )

assignment operator

Definition at line 140 of file spxweightst.h.

References SPxWeightST::colUp, SPxWeightST::colWeight, SPxWeightST::coWeight, SPxWeightST::forbidden, SPxWeightST::isConsistent(), SPxStarter::operator=(), SPxWeightST::rowRight, SPxWeightST::rowWeight, and SPxWeightST::weight.

Referenced by SPxVectorST::operator=().

void setPrimalStatus	(	SPxBasis::Desc &	desc,
		const SPxSolver &	base,
		const SPxId &	id
	)

private

Definition at line 63 of file spxweightst.cpp.

References SPxBasis::Desc::colStatus(), SPxWeightST::colUp, SPxSolver::epsilon(), soplex::infinity, SPxLP::lhs(), SPxLP::number(), SPxBasis::Desc::P_FIXED, SPxBasis::Desc::P_FREE, SPxBasis::Desc::P_ON_LOWER, SPxBasis::Desc::P_ON_UPPER, SPxLP::rhs(), SPxWeightST::rowRight, and SPxBasis::Desc::rowStatus().

Referenced by SPxWeightST::generate().

void setupWeights ( SPxSolver & base )

protectedvirtual

sets up variable weights.

This method is called in order to setup the weights for all variables. It has been declared virtual in order to allow for derived classes to compute other weight values.

Todo:: The comments are wrong. The first is for dual simplex and the secound for primal one. Is anything else wrong? Also the values are nearly the same for both cases. Should this be ? Changed the values for r_fixed to 0 because of maros-r7. It is not clear why this makes a difference because all constraints in that instance are of equality type. Why is rowRight sometimes not set?

Reimplemented in SPxVectorST, and SPxSumST.

Definition at line 414 of file spxweightst.cpp.

References SPxWeightST::colUp, SPxLP::colVector(), SPxWeightST::colWeight, Vector::dim(), SPxSolver::epsilon(), soplex::infinity, SPxLP::lhs(), Vector::maxAbs(), SPxLP::maxObj(), MSG_DEBUG, SPxLP::nCols(), SPxLP::nRows(), SPxSolver::rep(), SPxLP::rhs(), SPxWeightST::rowRight, SPxLP::rowVector(), SPxWeightST::rowWeight, SVector::size(), soplex::spxout, and SPxSolver::type().