doubleton_action Class Reference

Solve ax+by=c for y and substitute y out of the problem. More...

#include <CoinPresolveDoubleton.hpp>

Inheritance diagram for doubleton_action:

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Collaboration diagram for doubleton_action:

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List of all members.

Classes
struct	action
Public Member Functions
const char *	name () const
	A name for debug printing.
void	postsolve (CoinPostsolveMatrix *prob) const
	Apply the postsolve transformation for this particular presolve action.
	~doubleton_action ()
Static Public Member Functions
static const CoinPresolveAction *	presolve (CoinPresolveMatrix , const CoinPresolveAction next)
Public Attributes
const int	nactions_
const action *const	actions_
Private Member Functions
	doubleton_action (int nactions, const action actions, const CoinPresolveAction next)

Detailed Description

Solve ax+by=c for y and substitute y out of the problem.

This moves the bounds information for y onto x, making y free and allowing us to substitute it away.

	   a x + b y = c
	   l1 <= x <= u1
	   l2 <= y <= u2	==>
	  
	   l2 <= (c - a x) / b <= u2
	   b/-a > 0 ==> (b l2 - c) / -a <= x <= (b u2 - c) / -a
	   b/-a < 0 ==> (b u2 - c) / -a <= x <= (b l2 - c) / -a

Definition at line 24 of file CoinPresolveDoubleton.hpp.