ILPSolver (illinois-cogcomp-nlp 3.1.29 API)

All Known Implementing Classes:

BeamSearch, GurobiHook, JLISCuttingPlaneILPSolverGurobi, OJalgoHook
```
public interface ILPSolver
```
Classes that implement this interface contain implementations of algorithms that solve Integer Linear Programming problems.

Author:

Nick Rizzolo

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`VERBOSITY_HIGH` A possible setting for `#verbosity`.
`static int`	`VERBOSITY_LOW` A possible setting for `#verbosity`.
`static int`	`VERBOSITY_NONE` A possible setting for `#verbosity`.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method and Description
`int`	`addBooleanVariable(double c)` Adds a new Boolean variable (an integer variable constrained to take either the value 0 or the value 1) with the specified coefficient in the objective function to the problem.
`int[]`	`addDiscreteVariable(double[] c)` Adds a general, multi-valued discrete variable, which is implemented as a set of Boolean variables, one per value of the discrete variable, with exactly one of those variables set `true` at any given time.
`void`	`addEqualityConstraint(int[] i, double[] a, double b)` Adds a new fixed constraint to the problem.
`void`	`addGreaterThanConstraint(int[] i, double[] a, double b)` Adds a new lower bounded constraint to the problem.
`int`	`addIntegerVariable(double c)` Adds a new Integer variable with the specified coefficient in the objective function to the problem.
`void`	`addLessThanConstraint(int[] i, double[] a, double b)` Adds a new upper bounded constraint to the problem.
`int`	`addRealVariable(double c)` Adds a new Real variable with the specified coefficient in the objective function to the problem.
`boolean`	`getBooleanValue(int index)` When the problem has been solved, use this method to retrieve the value of any Boolean inference variable.
`int`	`getIntegerValue(int index)` When the problem has been solved, use this method to retrieve the value of any Integer inference variable.
`double`	`getRealValue(int index)` When the problem has been solved, use this method to retrieve the value of any Real inference variable.
`boolean`	`isSolved()` Tests whether the problem represented by this `ILPSolver` instance has been solved already.
`double`	`objectiveCoeff(int index)` The coefficient of the variable in the objective function.
`double`	`objectiveValue()` When the problem has been solved, use this method to retrieve the value of the objective function at the solution.
`void`	`reset()` This method clears the all constraints and variables out of the ILP solver's problem representation, bringing the `ILPSolver` instance back to the state it was in when first constructed.
`void`	`setMaximize(boolean d)` Sets the direction of the objective function.
`boolean`	`solve()` Solves the ILP problem, saving the solution internally.
`void`	`write(StringBuffer buffer)` Creates a textual representation of the ILP problem in an algebraic notation.

- Field Detail
  - VERBOSITY_NONE
```
static final int VERBOSITY_NONE
```
    A possible setting for #verbosity.
    
    See Also:
    
    Constant Field Values
  - VERBOSITY_LOW
```
static final int VERBOSITY_LOW
```
    A possible setting for #verbosity.
    
    See Also:
    
    Constant Field Values
  - VERBOSITY_HIGH
```
static final int VERBOSITY_HIGH
```
    A possible setting for #verbosity.
    
    See Also:
    
    Constant Field Values
- Method Detail
  - setMaximize
```
void setMaximize(boolean d)
```
    Sets the direction of the objective function.
    
    Parameters:
    
    d - true if the objective function is to be maximized.
  - addBooleanVariable
```
int addBooleanVariable(double c)
```
    Adds a new Boolean variable (an integer variable constrained to take either the value 0 or the value 1) with the specified coefficient in the objective function to the problem.
    
    Parameters:
    
    c - The objective function coefficient for the new Boolean variable.
    
    Returns:
    
    The indexes of the created variable.
  - addRealVariable
```
int addRealVariable(double c)
```
    Adds a new Real variable with the specified coefficient in the objective function to the problem.
    
    Parameters:
    
    c - The objective function coefficient for the new Real variable.
    
    Returns:
    
    The indexes of the created variable.
  - addIntegerVariable
```
int addIntegerVariable(double c)
```
    Adds a new Integer variable with the specified coefficient in the objective function to the problem.
    
    Parameters:
    
    c - The objective function coefficient for the new Integer variable.
    
    Returns:
    
    The indexes of the created variable.
  - addDiscreteVariable
```
int[] addDiscreteVariable(double[] c)
```
    Adds a general, multi-valued discrete variable, which is implemented as a set of Boolean variables, one per value of the discrete variable, with exactly one of those variables set true at any given time.
    
    Parameters:
    
    c - The objective function coefficients for the new Boolean variables.
    
    Returns:
    
    The indexes of the newly created variables.
  - addEqualityConstraint
```
void addEqualityConstraint(int[] i,
                           double[] a,
                           double b)
```
    Adds a new fixed constraint to the problem. The two array arguments must be the same length, as their elements correspond to each other. Variables whose coefficients are zero need not be mentioned. Variables that are mentioned must have previously been added via addBooleanVariable(double) or addDiscreteVariable(double[]). The resulting constraint has the form:
    x_i * a = b
    where x_i represents the inference variables whose indexes are contained in the array i and * represents dot product.
    
    Parameters:
    
    i - The indexes of the variables with non-zero coefficients.
    
    a - The coefficients of the variables with the given indexes.
    
    b - The new constraint will enforce equality with this constant.
  - addGreaterThanConstraint
```
void addGreaterThanConstraint(int[] i,
                              double[] a,
                              double b)
```
    Adds a new lower bounded constraint to the problem. The two array arguments must be the same length, as their elements correspond to each other. Variables whose coefficients are zero need not be mentioned. Variables that are mentioned must have previously been added via addBooleanVariable(double) or addDiscreteVariable(double[]). The resulting constraint has the form:
    x_i * a >= b
    where x_i represents the inference variables whose indexes are contained in the array i and * represents dot product.
    
    Parameters:
    
    i - The indexes of the variables with non-zero coefficients.
    
    a - The coefficients of the variables with the given indexes.
    
    b - The lower bound for the new constraint.
  - addLessThanConstraint
```
void addLessThanConstraint(int[] i,
                           double[] a,
                           double b)
```
    Adds a new upper bounded constraint to the problem. The two array arguments must be the same length, as their elements correspond to each other. Variables whose coefficients are zero need not be mentioned. Variables that are mentioned must have previously been added via addBooleanVariable(double) or addDiscreteVariable(double[]). The resulting constraint has the form:
    x_i * a <= b
    where x_i represents the inference variables whose indexes are contained in the array i and * represents dot product.
    
    Parameters:
    
    i - The indexes of the variables with non-zero coefficients.
    
    a - The coefficients of the variables with the given indexes.
    
    b - The upper bound for the new constraint.
  - solve
```
boolean solve()
       throws Exception
```
    Solves the ILP problem, saving the solution internally. This method may throw an exception if something doesn't go right.
    
    Throws:
    
    Exception
  - isSolved
```
boolean isSolved()
```
    Tests whether the problem represented by this ILPSolver instance has been solved already.
  - getBooleanValue
```
boolean getBooleanValue(int index)
```
    When the problem has been solved, use this method to retrieve the value of any Boolean inference variable. The result of this method is undefined when the problem has not yet been solved.
    
    Parameters:
    
    index - The index of the variable whose value is requested.
    
    Returns:
    
    The value of the variable.
  - getIntegerValue
```
int getIntegerValue(int index)
```
    When the problem has been solved, use this method to retrieve the value of any Integer inference variable. The result of this method is undefined when the problem has not yet been solved.
    
    Parameters:
    
    index - The index of the variable whose value is requested.
    
    Returns:
    
    The value of the variable.
  - getRealValue
```
double getRealValue(int index)
```
    When the problem has been solved, use this method to retrieve the value of any Real inference variable. The result of this method is undefined when the problem has not yet been solved.
    
    Parameters:
    
    index - The index of the variable whose value is requested.
    
    Returns:
    
    The value of the variable.
  - objectiveValue
```
double objectiveValue()
```
    When the problem has been solved, use this method to retrieve the value of the objective function at the solution. The result of this method is undefined when the problem has not yet been solved. If the problem had no feasible solutions, negative (positive, respectively) infinity will be returned if maximizing (minimizing).
    
    Returns:
    
    The value of the objective function at the solution.
  - objectiveCoeff
```
double objectiveCoeff(int index)
```
    The coefficient of the variable in the objective function.
  - reset
```
void reset()
```
    This method clears the all constraints and variables out of the ILP solver's problem representation, bringing the ILPSolver instance back to the state it was in when first constructed.
  - write
```
void write(StringBuffer buffer)
```
    Creates a textual representation of the ILP problem in an algebraic notation.
    
    Parameters:
    
    buffer - The created textual representation will be appended here.

Interface ILPSolver

Field Summary

Method Summary

Field Detail

VERBOSITY_NONE

VERBOSITY_LOW

VERBOSITY_HIGH

Method Detail

setMaximize

addBooleanVariable

addRealVariable

addIntegerVariable

addDiscreteVariable

addEqualityConstraint

addGreaterThanConstraint

addLessThanConstraint

solve

isSolved

getBooleanValue

getIntegerValue

getRealValue

objectiveValue

objectiveCoeff

reset

write