Module ojalgo

Package org.ojalgo.optimisation

Class Presolvers

java.lang.Object

org.ojalgo.optimisation.Presolvers

public abstract class Presolvers
extends Object

Field Summary

Fields

Modifier and Type	Field	Description
static final ExpressionsBasedModel.Presolver	INTEGER
static final ExpressionsBasedModel.Presolver	LINEAR_OBJECTIVE	If the expression is linear and contributes to the objective function, then the contributions are transferred to the variables and the weight of the expression set to null.
static final ExpressionsBasedModel.Presolver	REDUNDANT_CONSTRAINT	Calculates the min and max value of this expression based on the variables' individual bounds.
static final org.ojalgo.optimisation.ExpressionsBasedModel.VariableAnalyser	UNREFERENCED	Verifies that the variable is actually referenced/used in some expression.
static final ExpressionsBasedModel.Presolver	ZERO_ONE_TWO	Looks for constraint expressions with 0, 1 or 2 non-fixed variables.

Constructor Summary

Constructors

Constructor	Description
Presolvers()

Method Summary

Modifier and Type	Method	Description
static void	checkFeasibility(Expression expression, Set<Structure1D.IntIndex> remaining, BigDecimal lower, BigDecimal upper, NumberContext precision, boolean relaxed)
static boolean	checkSimilarity(Collection<Expression> current, Expression potential)	Checks if the potential Expression is similar to any in the current collection.
static boolean	reduce(Collection<Expression> expressions)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

INTEGER

public static final ExpressionsBasedModel.Presolver INTEGER

LINEAR_OBJECTIVE

public static final ExpressionsBasedModel.Presolver LINEAR_OBJECTIVE

If the expression is linear and contributes to the objective function, then the contributions are transferred to the variables and the weight of the expression set to null.

REDUNDANT_CONSTRAINT

public static final ExpressionsBasedModel.Presolver REDUNDANT_CONSTRAINT

Calculates the min and max value of this expression based on the variables' individual bounds. Then compares those with the expression's bounds.

UNREFERENCED

public static final org.ojalgo.optimisation.ExpressionsBasedModel.VariableAnalyser UNREFERENCED

Verifies that the variable is actually referenced/used in some expression. If not then that variable can either be fixed or marked as unbounded.

 2019-02-15: Turned this off. Very slow for large models
 2019-02-22: Turned this on again, different implementation
 

ZERO_ONE_TWO

public static final ExpressionsBasedModel.Presolver ZERO_ONE_TWO

Looks for constraint expressions with 0, 1 or 2 non-fixed variables. Transfers the constraints of the expressions to the variables and then (if possible) marks the expression as redundant.

Constructor Details

Presolvers

public Presolvers()

Method Details

checkFeasibility

public static void checkFeasibility(Expression expression,
 Set<Structure1D.IntIndex> remaining,
 BigDecimal lower,
 BigDecimal upper,
 NumberContext precision,
 boolean relaxed)

checkSimilarity

public static boolean checkSimilarity(Collection<Expression> current,
 Expression potential)

Checks if the potential Expression is similar to any in the current collection. Only works for linear expressions. If the potential expression to check has any quadratic term, nothing more is checked, and false is returned.

Returns:

true, if the potential Expression is found to be similar and marked as redundant by this method.

reduce

public static boolean reduce(Collection<Expression> expressions)