MipSolver Class Reference

Detailed Description

This class is an abstract base class for MIP solvers. This class provides a full interface for set and modify an MIP problem, solve it and retrieve the solution. You can use one of the descendants as a concrete implementation, or the Lp default MIP solver. However, if you would like to handle MIP solvers as reference or pointer in a generic way, you can use this class directly.

#include <lemon/lp_base.h>

Inheritance diagram for MipSolver:

Set Column Type
enum	ColTypes { REAL = 0, INTEGER = 1 }
	Possible variable (column) types (e.g. real, integer, binary etc.) More...
void	colType (Col c, ColTypes col_type)
ColTypes	colType (Col c) const

Public Types
enum	ProblemType {   UNDEFINED = 0, INFEASIBLE = 1, FEASIBLE = 2, OPTIMAL = 3,   UNBOUNDED = 4 }
	The problem types for MIP problems. More...
Public Types inherited from LpBase
enum	SolveExitStatus { SOLVED = 0, UNSOLVED = 1 }
	Possible outcomes of an LP solving procedure. More...
enum	Sense { MIN, MAX }
	Direction of the optimization. More...
enum	MessageLevel {   MESSAGE_NOTHING, MESSAGE_ERROR, MESSAGE_WARNING, MESSAGE_NORMAL,   MESSAGE_VERBOSE }
	Enum for messageLevel() parameter. More...
typedef double	Value
	The floating point type used by the solver.

Public Member Functions
virtual MipSolver *	newSolver () const =0
	Allocate a new MIP problem instance.
virtual MipSolver *	cloneSolver () const =0
	Make a copy of the MIP problem.
Solve the MIP
SolveExitStatus	solve ()
Obtain the Solution
ProblemType	type () const
	The type of the MIP problem.
Value	sol (Col c) const
	Return the value of the row in the solution.
Value	sol (const Expr &e) const
	Return the value of the expression in the solution.
Value	solValue () const
	The value of the objective function.
Public Member Functions inherited from LpBase
virtual	~LpBase ()
	Virtual destructor.
const char *	solverName () const
	Gives back the name of the solver.
Col	addCol ()
	Add a new empty column (i.e a new variable) to the LP.
template<class T >
int	addColSet (T &t)
	Adds several new columns (i.e variables) at once.
void	col (Col c, const DualExpr &e)
	Set a column (i.e a dual constraint) of the LP.
DualExpr	col (Col c) const
	Get a column (i.e a dual constraint) of the LP.
Col	addCol (const DualExpr &e, Value o=0)
	Add a new column to the LP.
Row	addRow ()
	Add a new empty row (i.e a new constraint) to the LP.
template<class T >
int	addRowSet (T &t)
	Add several new rows (i.e constraints) at once.
void	row (Row r, Value l, const Expr &e, Value u)
	Set a row (i.e a constraint) of the LP.
void	row (Row r, const Constr &c)
	Set a row (i.e a constraint) of the LP.
Expr	row (Row r) const
	Get a row (i.e a constraint) of the LP.
Row	addRow (Value l, const Expr &e, Value u)
	Add a new row (i.e a new constraint) to the LP.
Row	addRow (const Constr &c)
	Add a new row (i.e a new constraint) to the LP.
void	erase (Col c)
	Erase a column (i.e a variable) from the LP.
void	erase (Row r)
	Erase a row (i.e a constraint) from the LP.
std::string	colName (Col c) const
	Get the name of a column.
void	colName (Col c, const std::string &name)
	Set the name of a column.
Col	colByName (const std::string &name) const
	Get the column by its name.
std::string	rowName (Row r) const
	Get the name of a row.
void	rowName (Row r, const std::string &name)
	Set the name of a row.
Row	rowByName (const std::string &name) const
	Get the row by its name.
void	coeff (Row r, Col c, Value val)
	Set an element of the coefficient matrix of the LP.
Value	coeff (Row r, Col c) const
	Get an element of the coefficient matrix of the LP.
void	colLowerBound (Col c, Value value)
	Set the lower bound of a column (i.e a variable)
Value	colLowerBound (Col c) const
	Get the lower bound of a column (i.e a variable)
template<class T >
void	colLowerBound (T &t, Value value)
	Set the lower bound of several columns (i.e variables) at once.
void	colUpperBound (Col c, Value value)
	Set the upper bound of a column (i.e a variable)
Value	colUpperBound (Col c) const
	Get the upper bound of a column (i.e a variable)
template<class T >
void	colUpperBound (T &t, Value value)
	Set the upper bound of several columns (i.e variables) at once.
void	colBounds (Col c, Value lower, Value upper)
	Set the lower and the upper bounds of a column (i.e a variable)
template<class T >
void	colBounds (T &t, Value lower, Value upper)
	Set the lower and the upper bound of several columns (i.e variables) at once.
void	rowLowerBound (Row r, Value value)
	Set the lower bound of a row (i.e a constraint)
Value	rowLowerBound (Row r) const
	Get the lower bound of a row (i.e a constraint)
void	rowUpperBound (Row r, Value value)
	Set the upper bound of a row (i.e a constraint)
Value	rowUpperBound (Row r) const
	Get the upper bound of a row (i.e a constraint)
void	objCoeff (Col c, Value v)
	Set an element of the objective function.
Value	objCoeff (Col c) const
	Get an element of the objective function.
void	obj (const Expr &e)
	Set the objective function.
Expr	obj () const
	Get the objective function.
void	sense (Sense sense)
	Set the direction of optimization.
Sense	sense () const
	Query the direction of the optimization.
void	max ()
	Set the sense to maximization.
void	min ()
	Set the sense to maximization.
void	clear ()
	Clear the problem.
void	messageLevel (MessageLevel level)
	Set the message level of the solver.
void	write (std::string file, std::string format="MPS") const
	Write the problem to a file in the given format.

Additional Inherited Members
Static Public Member Functions inherited from LpBase
static int	id (const Col &col)
	Returns the ID of the column.
static Col	colFromId (int id)
	Returns the column with the given ID.
static int	id (const Row &row)
	Returns the ID of the row.
static Row	rowFromId (int id)
	Returns the row with the given ID.
Static Public Attributes inherited from LpBase
static const Value	INF
	The infinity constant.
static const Value	NaN
	The not a number constant.

Member Enumeration Documentation

enum ProblemType

Enumerator:

UNDEFINED	= 0. Feasible solution hasn't been found (but may exist).
INFEASIBLE	= 1. The problem has no feasible solution.
FEASIBLE	= 2. Feasible solution found.
OPTIMAL	= 3. Optimal solution exists and found.
UNBOUNDED	= 4. The cost function is unbounded. The Mip or at least the relaxed problem is unbounded.

enum ColTypes

Enumerator:

REAL	= 0. Continuous variable (default).
INTEGER	= 1. Integer variable.

Member Function Documentation

SolveExitStatus solve ( )

inline

Solve the MIP problem at hand

Returns

The result of the optimization procedure. Possible values and their meanings can be found in the documentation of SolveExitStatus.

void colType ( Col  c, ColTypes  col_type  )

inline

Sets the type of the given column to the given type.

ColTypes colType ( Col  c ) const

inline

Gives back the type of the column.

Value sol ( Col  c ) const

inline

Return the value of the row in the solution.

Precondition

The problem is solved.

Value sol ( const Expr &  e ) const

inline

Return the value of the expression in the solution, i.e. the dot product of the solution and the expression.

Precondition

The problem is solved.

Value solValue ( ) const

inline

Returns

• INF or -INF means either infeasibility or unboundedness of the problem, depending on whether we minimize or maximize.
• NaN if no primal solution is found.
• The (finite) objective value if an optimal solution is found.