CoinWarmStartBasis Class Reference

The default COIN simplex (basis-oriented) warm start class. More...

#include <CoinWarmStartBasis.hpp>

Inheritance diagram for CoinWarmStartBasis:

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Collaboration diagram for CoinWarmStartBasis:

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List of all members.

Public Types
enum	Status { isFree = 0x00, basic = 0x01, atUpperBound = 0x02, atLowerBound = 0x03 }
	Enum for status of variables. More...
typedef CoinTriple< int, int, int >	XferEntry
	Transfer vector entry for mergeBasis(const CoinWarmStartBasis,const XferVec,const XferVec*).
typedef std::vector< XferEntry >	XferVec
	Transfer vector for mergeBasis(const CoinWarmStartBasis,const XferVec,const XferVec*).
Public Member Functions
Methods to get and set basis information.
The status of variables is kept in a pair of arrays, one for structural variables, and one for artificials (aka logicals and slacks). The status is coded using the values of the Status enum. See also: CoinWarmStartBasis::Status for a description of the packing used in the status arrays.
int	getNumStructural () const
	Return the number of structural variables.
int	getNumArtificial () const
	Return the number of artificial variables.
int	numberBasicStructurals () const
	Return the number of basic structurals.
Status	getStructStatus (int i) const
	Return the status of the specified structural variable.
void	setStructStatus (int i, Status st)
	Set the status of the specified structural variable.
char *	getStructuralStatus ()
	Return the status array for the structural variables.
const char *	getStructuralStatus () const
	`const` overload for getStructuralStatus()
char *	getArtificialStatus ()
	As for getStructuralStatus , but returns the status array for the artificial variables.
Status	getArtifStatus (int i) const
	Return the status of the specified artificial variable.
void	setArtifStatus (int i, Status st)
	Set the status of the specified artificial variable.
const char *	getArtificialStatus () const
	`const` overload for getArtificialStatus()
Basis `diff' methods

virtual CoinWarmStartDiff *	generateDiff (const CoinWarmStart *const oldCWS) const
	Generate a `diff' that can convert the warm start basis passed as a parameter to the warm start basis specified by `this`.
virtual void	applyDiff (const CoinWarmStartDiff *const cwsdDiff)
	Apply `diff` to this basis.
Methods to modify the warm start object

virtual void	setSize (int ns, int na)
	Set basis capacity; existing basis is discarded.
virtual void	resize (int newNumberRows, int newNumberColumns)
	Set basis capacity; existing basis is maintained.
virtual void	compressRows (int tgtCnt, const int *tgts)
	Delete a set of rows from the basis.
virtual void	deleteRows (int rawTgtCnt, const int *rawTgts)
	Delete a set of rows from the basis.
virtual void	deleteColumns (int number, const int *which)
	Delete a set of columns from the basis.
virtual void	mergeBasis (const CoinWarmStartBasis src, const XferVec xferRows, const XferVec *xferCols)
	Merge entries from a source basis into this basis.
Constructors, destructors, and related functions

	CoinWarmStartBasis ()
	Default constructor.
	CoinWarmStartBasis (int ns, int na, const char sStat, const char aStat)
	Constructs a warm start object with the specified status vectors.
	CoinWarmStartBasis (const CoinWarmStartBasis &ws)
	Copy constructor.
virtual CoinWarmStart *	clone () const
	`Virtual constructor'
virtual	~CoinWarmStartBasis ()
	Destructor.
virtual CoinWarmStartBasis &	operator= (const CoinWarmStartBasis &rhs)
	Assignment.
virtual void	assignBasisStatus (int ns, int na, char &sStat, char &aStat)
	Assign the status vectors to be the warm start information.
Miscellaneous methods

virtual void	print () const
	Prints in readable format (for debug).
Protected Attributes
Protected data members
See also: CoinWarmStartBasis::Status for a description of the packing used in the status arrays.
int	numStructural_
	The number of structural variables.
int	numArtificial_
	The number of artificial variables.
int	maxSize_
	The maximum sise (in ints - actually 4*char) (so resize does not need to do new).
char *	structuralStatus_
	The status of the structural variables.
char *	artificialStatus_
	The status of the artificial variables.
Related Functions
(Note that these are not member functions.)
CoinWarmStartBasis::Status	getStatus (const char *array, int i)
	Get the status of the specified variable in the given status array.
void	setStatus (char *array, int i, CoinWarmStartBasis::Status st)
	Set the status of the specified variable in the given status array.

Detailed Description

The default COIN simplex (basis-oriented) warm start class.

CoinWarmStartBasis provides for a warm start object which contains the status of each variable (structural and artificial).

Todo:: Modify this class so that the number of status entries per byte and bytes per status vector allocation unit are not hardcoded. At the least, collect this into a couple of macros.

Todo:: Consider separate fields for allocated capacity and actual basis size. We could avoid some reallocation, at the price of retaining more space than we need. Perhaps more important, we could do much better sanity checks.

Definition at line 38 of file CoinWarmStartBasis.hpp.

Member Typedef Documentation

typedef CoinTriple<int,int,int> CoinWarmStartBasis::XferEntry

Transfer vector entry for mergeBasis(const CoinWarmStartBasis*,const XferVec*,const XferVec*).

Definition at line 65 of file CoinWarmStartBasis.hpp.

typedef std::vector<XferEntry> CoinWarmStartBasis::XferVec

Transfer vector for mergeBasis(const CoinWarmStartBasis*,const XferVec*,const XferVec*).

Definition at line 70 of file CoinWarmStartBasis.hpp.

Member Enumeration Documentation

enum CoinWarmStartBasis::Status

Enum for status of variables.

Matches CoinPrePostsolveMatrix::Status, without superBasic. Most code that converts between CoinPrePostsolveMatrix::Status and CoinWarmStartBasis::Status will break if this correspondence is broken.

The status vectors are currently packed using two bits per status code, four codes per byte. The location of the status information for variable i is in byte i>>2 and occupies bits 0:1 if i%4 == 0, bits 2:3 if i%4 == 1, etc. The non-member functions getStatus(const char*,int) and setStatus(char*,int,CoinWarmStartBasis::Status) are provided to hide details of the packing.

Enumerator:

isFree	Nonbasic free variable.
basic	Basic variable.
atUpperBound	Nonbasic at upper bound.
atLowerBound	Nonbasic at lower bound.

Definition at line 55 of file CoinWarmStartBasis.hpp.

Constructor & Destructor Documentation

CoinWarmStartBasis::CoinWarmStartBasis ( )

Default constructor.

Creates a warm start object representing an empty basis (0 rows, 0 columns).

CoinWarmStartBasis::CoinWarmStartBasis	(	int	ns,
		int	na,
		const char *	sStat,
		const char *	aStat
	)

Constructs a warm start object with the specified status vectors.

The parameters are copied. Consider assignBasisStatus(int,int,char*&,char*&) if the object should assume ownership.

See also:: CoinWarmStartBasis::Status for a description of the packing used in the status arrays.

CoinWarmStartBasis::CoinWarmStartBasis ( const CoinWarmStartBasis & ws )

Copy constructor.

virtual CoinWarmStartBasis::~CoinWarmStartBasis ( ) [virtual]

Destructor.

Member Function Documentation

int CoinWarmStartBasis::getNumStructural ( ) const [inline]

Return the number of structural variables.

Definition at line 85 of file CoinWarmStartBasis.hpp.

int CoinWarmStartBasis::getNumArtificial ( ) const [inline]

Return the number of artificial variables.

Definition at line 88 of file CoinWarmStartBasis.hpp.

int CoinWarmStartBasis::numberBasicStructurals ( ) const

Return the number of basic structurals.

A fast test for an all-slack basis.

Status CoinWarmStartBasis::getStructStatus ( int i ) const [inline]

Return the status of the specified structural variable.

Definition at line 97 of file CoinWarmStartBasis.hpp.

void CoinWarmStartBasis::setStructStatus	(	int	i,
		Status	st
	)			`[inline]`

Set the status of the specified structural variable.

Definition at line 103 of file CoinWarmStartBasis.hpp.

char* CoinWarmStartBasis::getStructuralStatus ( ) [inline]

Return the status array for the structural variables.

The status information is stored using the codes defined in the Status enum, 2 bits per variable, packed 4 variables per byte.

Definition at line 114 of file CoinWarmStartBasis.hpp.

const char* CoinWarmStartBasis::getStructuralStatus ( ) const [inline]

const overload for getStructuralStatus()

Definition at line 121 of file CoinWarmStartBasis.hpp.

char* CoinWarmStartBasis::getArtificialStatus ( ) [inline]

As for getStructuralStatus , but returns the status array for the artificial variables.

Definition at line 126 of file CoinWarmStartBasis.hpp.

Status CoinWarmStartBasis::getArtifStatus ( int i ) const [inline]

Return the status of the specified artificial variable.

Definition at line 129 of file CoinWarmStartBasis.hpp.

void CoinWarmStartBasis::setArtifStatus	(	int	i,
		Status	st
	)			`[inline]`

Set the status of the specified artificial variable.

Definition at line 135 of file CoinWarmStartBasis.hpp.

const char* CoinWarmStartBasis::getArtificialStatus ( ) const [inline]

const overload for getArtificialStatus()

Definition at line 146 of file CoinWarmStartBasis.hpp.

virtual CoinWarmStartDiff* CoinWarmStartBasis::generateDiff ( const CoinWarmStart *const oldCWS ) const [virtual]

Generate a `diff' that can convert the warm start basis passed as a parameter to the warm start basis specified by this.

The capabilities are limited: the basis passed as a parameter can be no larger than the basis pointed to by this.

Reimplemented in OsiDylpWarmStartBasis.

virtual void CoinWarmStartBasis::applyDiff ( const CoinWarmStartDiff *const cwsdDiff ) [virtual]

Apply diff to this basis.

Update this basis by applying diff. It's assumed that the allocated capacity of the basis is sufficiently large.

Reimplemented from CoinWarmStart.

Reimplemented in OsiDylpWarmStartBasis.

virtual void CoinWarmStartBasis::setSize	(	int	ns,
		int	na
	)			`[virtual]`

Set basis capacity; existing basis is discarded.

After execution of this routine, the warm start object does not describe a valid basis: all structural and artificial variables have status isFree.

Reimplemented in OsiDylpWarmStartBasis.

virtual void CoinWarmStartBasis::resize	(	int	newNumberRows,
		int	newNumberColumns
	)			`[virtual]`

Set basis capacity; existing basis is maintained.

After execution of this routine, the warm start object describes a valid basis: the status of new structural variables (added columns) is set to nonbasic at lower bound, and the status of new artificial variables (added rows) is set to basic. (The basis can be invalid if new structural variables do not have a finite lower bound.)

Reimplemented in OsiDylpWarmStartBasis.

virtual void CoinWarmStartBasis::compressRows	(	int	tgtCnt,
		const int *	tgts
	)			`[virtual]`

Delete a set of rows from the basis.

Warning:: This routine assumes that the set of indices to be deleted is sorted in ascending order and contains no duplicates. Use deleteRows() if this is not the case.; The resulting basis is guaranteed valid only if all deleted constraints are slack (hence the associated logicals are basic).

Removal of a tight constraint with a nonbasic logical implies that some basic variable must be made nonbasic. This correction is left to the client.

Reimplemented in OsiDylpWarmStartBasis.

virtual void CoinWarmStartBasis::deleteRows	(	int	rawTgtCnt,
		const int *	rawTgts
	)			`[virtual]`

Delete a set of rows from the basis.

Warning:: The resulting basis is guaranteed valid only if all deleted constraints are slack (hence the associated logicals are basic).

Removal of a tight constraint with a nonbasic logical implies that some basic variable must be made nonbasic. This correction is left to the client.

Reimplemented in OsiDylpWarmStartBasis.

virtual void CoinWarmStartBasis::deleteColumns	(	int	number,
		const int *	which
	)			`[virtual]`

Delete a set of columns from the basis.

Warning:: The resulting basis is guaranteed valid only if all deleted variables are nonbasic.

Removal of a basic variable implies that some nonbasic variable must be made basic. This correction is left to the client.

virtual void CoinWarmStartBasis::mergeBasis	(	const CoinWarmStartBasis *	src,
		const XferVec *	xferRows,
		const XferVec *	xferCols
	)			`[virtual]`

Merge entries from a source basis into this basis.

Warning:: It's the client's responsibility to ensure validity of the merged basis, if that's important to the application.

The vector xferCols (xferRows) specifies runs of entries to be taken from the source basis and placed in this basis. Each entry is a CoinTriple, with first specifying the starting source index of a run, second specifying the starting destination index, and third specifying the run length.

virtual CoinWarmStart* CoinWarmStartBasis::clone ( ) const [inline, virtual]

`Virtual constructor'

Implements CoinWarmStart.

Reimplemented in OsiDylpWarmStartBasis.

Definition at line 282 of file CoinWarmStartBasis.hpp.

virtual CoinWarmStartBasis& CoinWarmStartBasis::operator= ( const CoinWarmStartBasis & rhs ) [virtual]

Assignment.

Reimplemented in OsiDylpWarmStartBasis.

virtual void CoinWarmStartBasis::assignBasisStatus	(	int	ns,
		int	na,
		char *&	sStat,
		char *&	aStat
	)			`[virtual]`

Assign the status vectors to be the warm start information.

In this method the CoinWarmStartBasis object assumes ownership of the pointers and upon return the argument pointers will be NULL. If copying is desirable, use the array constructor or the assignment operator .