Detect and process implied free variables. More...
#include <CoinPresolveImpliedFree.hpp>
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. | |
virtual | ~implied_free_action () |
Static Public Member Functions | |
static const CoinPresolveAction * | presolve (CoinPresolveMatrix *prob, const CoinPresolveAction *next, int &fillLevel) |
Detect and process implied free variables.
Consider a singleton variable x (i.e., a variable involved in only one constraint). Suppose that the bounds on that constraint, combined with the bounds on the other variables involved in the constraint, are such that even the worst case values of the other variables still imply bounds for x which are tighter than the variable's original bounds. Since x can never reach its upper or lower bounds, it is an implied free variable. Both x and the constraint can be deleted from the problem.
A similar transform for the case where the variable is not a natural column singleton is handled by subst_constraint_action.
Definition at line 29 of file CoinPresolveImpliedFree.hpp.
virtual implied_free_action::~implied_free_action | ( | ) | [virtual] |
const char* implied_free_action::name | ( | ) | const [virtual] |
A name for debug printing.
It is expected that the name is not stored in the transform itself.
Implements CoinPresolveAction.
static const CoinPresolveAction* implied_free_action::presolve | ( | CoinPresolveMatrix * | prob, | |
const CoinPresolveAction * | next, | |||
int & | fillLevel | |||
) | [static] |
void implied_free_action::postsolve | ( | CoinPostsolveMatrix * | prob | ) | const [virtual] |
Apply the postsolve transformation for this particular presolve action.
Implements CoinPresolveAction.