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MipSolver Class Referenceabstract

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 MipSolvernewSolver () const =0
 Allocate a new MIP problem instance.
 
virtual MipSolvercloneSolver () 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

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.