CoinUtils
trunk
|
Fix a variable at a specified bound. More...
#include <CoinPresolveFixed.hpp>
Classes | |
struct | action |
Structure to preserve the bound overwritten when fixing a variable. | |
Public Member Functions | |
const char * | name () const |
Returns string "make_fixed_action". | |
void | postsolve (CoinPostsolveMatrix *prob) const |
Postsolve (unfix variables) | |
virtual | ~make_fixed_action () |
Destructor. | |
Static Public Member Functions | |
static const CoinPresolveAction * | presolve (CoinPresolveMatrix *prob, int *fcols, int nfcols, bool fix_to_lower, const CoinPresolveAction *next) |
Perform actions to fix variables and return postsolve object. | |
Related Functions | |
(Note that these are not member functions.) | |
const CoinPresolveAction * | make_fixed (CoinPresolveMatrix *prob, const CoinPresolveAction *next) |
Scan variables and fix any with equal bounds. | |
void | transferCosts (CoinPresolveMatrix *prob) |
Transfer costs from singleton variables. |
Fix a variable at a specified bound.
Implements the action of fixing a variable by forcing both bounds to the same value and forcing the value of the variable to match.
If the bounds are already equal, and the value of the variable is already correct, consider remove_fixed_action.
Definition at line 95 of file CoinPresolveFixed.hpp.
virtual make_fixed_action::~make_fixed_action | ( | ) | [inline, virtual] |
Destructor.
Definition at line 153 of file CoinPresolveFixed.hpp.
const char* make_fixed_action::name | ( | ) | const [virtual] |
Returns string "make_fixed_action".
Implements CoinPresolveAction.
static const CoinPresolveAction* make_fixed_action::presolve | ( | CoinPresolveMatrix * | prob, |
int * | fcols, | ||
int | nfcols, | ||
bool | fix_to_lower, | ||
const CoinPresolveAction * | next | ||
) | [static] |
Perform actions to fix variables and return postsolve object.
For each specified variable (nfcols
, fcols
), fix the variable to the specified bound (fix_to_lower
) by setting the variable's bounds to be equal in prob
. Create a postsolve object, link it at the head of the list of postsolve objects (next
), and return the object.
void make_fixed_action::postsolve | ( | CoinPostsolveMatrix * | prob | ) | const [virtual] |
Postsolve (unfix variables)
Back out the variables fixed by the presolve side of this object.
Implements CoinPresolveAction.
const CoinPresolveAction * make_fixed | ( | CoinPresolveMatrix * | prob, |
const CoinPresolveAction * | next | ||
) | [related] |
Scan variables and fix any with equal bounds.
A front end to collect a list of columns with equal bounds and hand them to make_fixed_action::presolve() for processing.
void transferCosts | ( | CoinPresolveMatrix * | prob | ) | [related] |
Transfer costs from singleton variables.
Transfers costs from singleton variables in equalities onto the other variables. Will also transfer costs from one integer variable to other integer variables with zero cost if there's a net gain in integer variables with non-zero cost.
The relation to make_fixed_action is tenuous, but this transform should be attempted before the initial round of variable fixing.