remove_fixed_action Class Reference

Excise fixed variables from the model. More...

#include <CoinPresolveFixed.hpp>

Inheritance diagram for remove_fixed_action:

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Collaboration diagram for remove_fixed_action:

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List of all members.

Classes
struct	action
	Structure to hold information necessary to reintroduce a column into the problem representation. More...
Public Member Functions
const char *	name () const
	Returns string "remove_fixed_action".
void	postsolve (CoinPostsolveMatrix *prob) const
	Apply the postsolve transformation for this particular presolve action.
	~remove_fixed_action ()
	Destructor.
Static Public Member Functions
static const remove_fixed_action *	presolve (CoinPresolveMatrix prob, int fcols, int nfcols, const CoinPresolveAction *next)
	Excise the specified columns.
Public Attributes
int *	colrows_
	Array of row indices for coefficients of excised columns.
double *	colels_
	Array of coefficients of excised columns.
int	nactions_
	Number of entries in actions_.
action *	actions_
	Vector specifying variable(s) affected by this object.
Private Member Functions
	remove_fixed_action (int nactions, action actions, double colels, int colrows, const CoinPresolveAction next)
	Constructor.
Related Functions
(Note that these are not member functions.)
const CoinPresolveAction *	remove_fixed (CoinPresolveMatrix prob, const CoinPresolveAction next)
	Scan the problem for fixed columns and remove them.

Detailed Description

Excise fixed variables from the model.

Implements the action of removing one or more fixed variables x_j from the model by substituting the value sol_j in each constraint. Specifically, for each constraint i where a_ij != 0, rlo_i and rup_i are adjusted by -a_ij*sol_j and a_ij is set to 0.

There is an implicit assumption that the variable already has the correct value. If this isn't true, corrections to row activity may be incorrect. If you want to guard against this possibility, consider make_fixed_action.

Actual removal of the column from the matrix is handled by drop_empty_cols_action. Correction of the objective function is done there.

Definition at line 23 of file CoinPresolveFixed.hpp.

Constructor & Destructor Documentation

remove_fixed_action::remove_fixed_action	(	int	nactions,
		action *	actions,
		double *	colels,
		int *	colrows,
		const CoinPresolveAction *	next
	)			`[private]`

Constructor.

remove_fixed_action::~remove_fixed_action ( )

Destructor.

Member Function Documentation

const char* remove_fixed_action::name ( ) const [virtual]

Returns string "remove_fixed_action".

Implements CoinPresolveAction.

static const remove_fixed_action* remove_fixed_action::presolve	(	CoinPresolveMatrix *	prob,
		int *	fcols,
		int	nfcols,
		const CoinPresolveAction *	next
	)			`[static]`

Excise the specified columns.

Remove the specified columns (nfcols, fcols) from the problem representation (prob), leaving the appropriate postsolve object linked as the head of the list of postsolve objects (currently headed by next).

void remove_fixed_action::postsolve ( CoinPostsolveMatrix * prob ) const [virtual]

Apply the postsolve transformation for this particular presolve action.

Implements CoinPresolveAction.