Class Variable

java.lang.Object

org.ojalgo.optimisation.ModelEntity<Variable>

org.ojalgo.optimisation.Variable

All Implemented Interfaces:

Comparable<Variable>, Optimisation, Optimisation.Constraint, Optimisation.Objective

public final class Variable
extends ModelEntity<Variable>

Variable represents a decision variable in an optimization model.

Each variable has a unique index in the model and can have:

• Lower and upper bounds (constraints)
• A contribution weight in the objective function
• An integer or continuous domain
• A current value

Variables can be configured as:

• Binary (0-1 integer variables)
• Integer (whole number values only)
• Continuous (any value within bounds)
• Fixed (equal lower and upper bounds)
• Unbounded (no effective limits)

As a subclass of ModelEntity, a Variable can function both as a constraint (through lower/upper bounds) and as an objective function component (through its contribution weight).

Variables are typically created and managed through ExpressionsBasedModel, which assigns their indices and incorporates them into the optimization problem.

Nested Class Summary

Nested classes/interfaces inherited from interface Optimisation

Optimisation.Constraint, Optimisation.ConstraintType, Optimisation.Integration<M,S>, Optimisation.Model, Optimisation.Objective, Optimisation.Options, Optimisation.ProblemStructure, Optimisation.Result, Optimisation.Sense, Optimisation.Solver, Optimisation.State

Field Summary

Fields

Modifier and Type	Field	Description
private final Structure1D.IntIndex	myIndex
private boolean	myInteger
private boolean	myUnbounded
private BigDecimal	myValue

Fields inherited from class ModelEntity

PRINT, RANGE

Constructor Summary

Constructors

Constructor	Description
Variable(String name, int index)
Variable(Variable variableToCopy)

Method Summary

Modifier and Type	Method	Description
void	addTo(Expression target, BigDecimal scale)	Add this (Variable or Expression) to another Expression, scaled by a factor.
protected void	appendMiddlePart(StringBuilder builder, NumberContext display)
private void	assertFixedValue()
Variable	binary()	See isBinary().
int	compareTo(Variable obj)
(package private) Variable	copy()	Internal copy that includes the index
(package private) int	deriveAdjustmentExponent()
protected void	destroy()
(package private) void	doIntegerRounding()	If necessary this method should first determine if this ModelEntity is "integer" or not.
boolean	equals(Object obj)
(package private) Structure1D.IntIndex	getIndex()
BigDecimal	getLowerSlack()
BigDecimal	getUpperSlack()
BigDecimal	getValue()
int	hashCode()
Variable	integer()
Variable	integer(boolean integer)	See isInteger().
boolean	isBinary()	Variable can only be 0 or 1.
(package private) boolean	isFixed()
boolean	isInteger()	Is this entity (all involved variables) integer?
boolean	isNegative()	The range includes something invalid input: '<' 0.0
boolean	isPositive()	The range includes something > 0.0
(package private) boolean	isUnbounded()
boolean	isValueSet()
Variable	lower(Comparable<?> lower)	Extremely large (absolute value) values are treated as "no limit" (null) and extremely small values are treated as exactly 0.0, unless the input number type is BigDecimal.
BigDecimal	quantifyContribution()
Variable	relax()
(package private) void	setFixed(BigDecimal value)
void	setInteger(boolean integer)
(package private) void	setUnbounded(boolean uncorrelated)
void	setValue(Comparable<?> value)
Variable	upper(Comparable<?> upper)	Extremely large (absolute value) values are treated as "no limit" (null) and extremely small values are treated as exactly 0.0, unless the input number type is BigDecimal.
protected boolean	validate(BigDecimal value, NumberContext context, BasicLogger appender)
(package private) boolean	validate(BigDecimal value, NumberContext context, BasicLogger appender, boolean relaxed)
Variable	value(BigDecimal value)

Methods inherited from class ModelEntity

adjust, appendLeftPart, appendRightPart, appendToString, deriveAdjustmentExponent, getAdjustmentExponent, getAdjustmentExponentValue, getAdjustmentFactor, getCompensatedLowerLimit, getCompensatedLowerLimit, getCompensatedUpperLimit, getCompensatedUpperLimit, getContributionWeight, getLowerLimit, getLowerLimit, getLowerLimit, getName, getUpperLimit, getUpperLimit, getUpperLimit, isClosedRange, isConstraint, isContributionWeightSet, isEqualityConstraint, isInfeasible, isInfeasible, isLowerConstraint, isLowerLimitSet, isObjective, isUpperConstraint, isUpperLimitSet, level, level, level, lower, lower, reverseAdjustment, shift, toAdjusted, toBigDecimal, toString, toUnadjusted, upper, upper, validate, weight, weight, weight

Methods inherited from class Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Details

myIndex

private final Structure1D.IntIndex myIndex

myInteger

private boolean myInteger

myUnbounded

private transient boolean myUnbounded

myValue

private BigDecimal myValue

Constructor Details

Variable

Variable(String name,
 int index)

Variable

Variable(Variable variableToCopy)

Method Details

addTo

public void addTo(Expression target,
 BigDecimal scale)

Description copied from class: ModelEntity

Add this (Variable or Expression) to another Expression, scaled by a factor.

Specified by:

addTo in class ModelEntity<Variable>

Parameters:

target - The target Expression

scale - The scaling factor

binary

public Variable binary()

See isBinary().

See Also:

• ModelEntity.getUpperLimit()
• isInteger()
• isBinary()

compareTo

public int compareTo(Variable obj)

equals

public boolean equals(Object obj)

Overrides:

equals in class ModelEntity<Variable>

getLowerSlack

public BigDecimal getLowerSlack()

getUpperSlack

public BigDecimal getUpperSlack()

getValue

public BigDecimal getValue()

hashCode

public int hashCode()

Overrides:

hashCode in class ModelEntity<Variable>

integer

public Variable integer()

integer

public Variable integer(boolean integer)

See isInteger().

isBinary

public boolean isBinary()

Variable can only be 0 or 1.

isInteger

public boolean isInteger()

Description copied from class: ModelEntity

Is this entity (all involved variables) integer?

Specified by:

isInteger in class ModelEntity<Variable>

Returns:

true if this is an integer variable, otherwise false

isNegative

public boolean isNegative()

The range includes something invalid input: '<' 0.0

isPositive

public boolean isPositive()

The range includes something > 0.0

isValueSet

public boolean isValueSet()

lower

public Variable lower(Comparable<?> lower)

Description copied from class: ModelEntity

Extremely large (absolute value) values are treated as "no limit" (null) and extremely small values are treated as exactly 0.0, unless the input number type is BigDecimal. BigDecimal values are always used as they are.

Overrides:

lower in class ModelEntity<Variable>

quantifyContribution

public BigDecimal quantifyContribution()

relax

public Variable relax()

setInteger

public void setInteger(boolean integer)

setValue

public void setValue(Comparable<?> value)

upper

public Variable upper(Comparable<?> upper)

Description copied from class: ModelEntity

Extremely large (absolute value) values are treated as "no limit" (null) and extremely small values are treated as exactly 0.0, unless the input number type is BigDecimal. BigDecimal values are always used as they are.

Overrides:

upper in class ModelEntity<Variable>

value

public Variable value(BigDecimal value)

assertFixedValue

private void assertFixedValue()

appendMiddlePart

protected void appendMiddlePart(StringBuilder builder,
 NumberContext display)

Overrides:

appendMiddlePart in class ModelEntity<Variable>

destroy

protected void destroy()

Overrides:

destroy in class ModelEntity<Variable>

validate

protected boolean validate(BigDecimal value,
 NumberContext context,
 BasicLogger appender)

Overrides:

validate in class ModelEntity<Variable>

copy

Variable copy()

Internal copy that includes the index

deriveAdjustmentExponent

int deriveAdjustmentExponent()

Specified by:

deriveAdjustmentExponent in class ModelEntity<Variable>

doIntegerRounding

void doIntegerRounding()

Description copied from class: ModelEntity

If necessary this method should first determine if this ModelEntity is "integer" or not.

If it is, then verify if all variable factors are integers or if there exists a simple scalar that will make it so. If so, the lower/upper limits are "integer rounded".

Specified by:

doIntegerRounding in class ModelEntity<Variable>

getIndex

Structure1D.IntIndex getIndex()

isFixed

boolean isFixed()

isUnbounded

boolean isUnbounded()

setFixed

void setFixed(BigDecimal value)

setUnbounded

void setUnbounded(boolean uncorrelated)

validate

boolean validate(BigDecimal value,
 NumberContext context,
 BasicLogger appender,
 boolean relaxed)