Abstract base class for reformulating a problem so that handlers can be applied to it. More...

#include <Transformer.h>

Inheritance diagram for Minotaur::Transformer:

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Collaboration diagram for Minotaur::Transformer:

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Public Member Functions
	Transformer ()
	Default Constructor.

	Transformer (EnvPtr env, ProblemPtr oldp)
	Constructor.

virtual	~Transformer ()
	Destroy.

virtual std::string	getName () const =0
	Get the name of this Transformer.

virtual SolutionPtr	getSolOrig (ConstSolutionPtr sol, int &err)=0
	Translate the solution of reformulated problem into that of original problem.

virtual SolutionPtr	getSolTrans (ConstSolutionPtr sol, int &err)=0
	Translate the solution of originial problem into that of reformulated problem.

virtual void	reformulate (ProblemPtr &newp, HandlerVector &handlers, int &status)=0
	Perform the reformulation, and assign handlers.

Protected Member Functions
bool	allConsAssigned_ (ProblemPtr p, HandlerVector &handlers)
	Check if all constraints in a problem have been assigned to a handler.

void	assignHandler_ (CGraphPtr cg, ConstraintPtr c)
	Assign an appropriate handler to a nonlinear constraint of the form .

void	clearUnusedHandlers_ (HandlerVector &handlers)
	Delete unused handlers.

void	copyLinear_ (ConstProblemPtr p, ProblemPtr newp)
	Copy all the linear constraints of the problem into the new problem.

void	copyVars_ (ConstProblemPtr p, ProblemPtr newp)
	Copy all the linear constraints of the problem into the new problem.

virtual void	makeObjLin_ ()

void	minObj_ ()
	Convert a maximization objective into minimization.

VariablePtr	newVar_ (VariablePtr iv, double d, ProblemPtr newp)
	Find the auxiliary variable associated with or create a new one.

VariablePtr	newVar_ (LinearFunctionPtr lf, double d, ProblemPtr newp)
	Find the auxiliary variable associated with or create a new one.

VariablePtr	newVar_ (CGraphPtr cg, ProblemPtr newp)
	Find the auxiliary variable associated with or create a new one.

Protected Attributes
EnvPtr	env_
	The pointer to environment.

LinearHandlerPtr	lHandler_
	Handler for linear constraints and variables.

LoggerPtr	logger_
	Logger.

ProblemPtr	newp_
	The transformed problem.

ProblemPtr	p_
	The original problem.

kPowHandlerPtr	kHandler_
	Handler for y = x^k type constraints.

QuadHandlerPtr	qHandler_
	Handler for quadratic terms.

CxUnivarHandlerPtr	uHandler_
	Handler for univariate constraints.

UnivarQuadHandlerPtr	uqHandler_
	Handler for univariate quadratic constraints.

YEqLFs *	yLfs_
	Storage for auxiliary variables defined by relations of the form .

YEqUCGs *	yUniExprs_
	Storage for auxiliary variables defined by relations of the form .

YEqVars *	yVars_
	Storage for auxiliary variables defined by relations of the form .

const double	zTol_
	Tolerance for checking if a value is zero.

Detailed Description

Abstract base class for reformulating a problem so that handlers can be applied to it.

A transformer will create a new problem equivalent to a given problem by spliting constraints, adding new variables etc. The end result is a problem whose each constraint can be handled by a specific handler. This class has some abstract virtual methods that must be implemented by a derived class. Other commonly used functions are implemented here.

Member Function Documentation

◆ allConsAssigned_()

bool Transformer::allConsAssigned_	(	ProblemPtr	p,
		HandlerVector &	handlers
	)

protected

Check if all constraints in a problem have been assigned to a handler.

Parameters

[in] p Problem whose constraints need to be checked.

Returns: True if all constraints have been assigned. False otherwise.

◆ assignHandler_()

void Transformer::assignHandler_	(	CGraphPtr	cg,
		ConstraintPtr	c
	)

protected

Assign an appropriate handler to a nonlinear constraint of the form $y_i = f(x)$ .

Parameters

[in]	cg	A nonlinear function which is be replaced by the auxiliary variable.
[in]	c	The nonlinear constraint that is being assigned to.

◆ clearUnusedHandlers_()

void Transformer::clearUnusedHandlers_ ( HandlerVector & handlers )

protected

Delete unused handlers.

Parameters

[in/out] handlers. Contains pointers to each handler. Unused ones are removed from the vector.

◆ copyLinear_()

void Transformer::copyLinear_	(	ConstProblemPtr	p,
		ProblemPtr	newp
	)

protected

Copy all the linear constraints of the problem into the new problem.

Parameters

[in]	p	Input problem
[in]	newp	The transformed problem to which new constraints are added.

◆ copyVars_()

void Transformer::copyVars_	(	ConstProblemPtr	p,
		ProblemPtr	newp
	)

protected

Copy all the linear constraints of the problem into the new problem.

Parameters

[in]	p	Input problem
[in]	newp	The transformed problem to which new constraints are added.

◆ getName()

virtual std::string Minotaur::Transformer::getName ( ) const

pure virtual

Get the name of this Transformer.

Implemented in Minotaur::QuadTransformer, Minotaur::SimpleTransformer, and Minotaur::TransPoly.

◆ getSolOrig()

virtual SolutionPtr Minotaur::Transformer::getSolOrig	(	ConstSolutionPtr	sol,
		int &	err
	)

pure virtual

Translate the solution of reformulated problem into that of original problem.

Parameters

[in]	sol	Solution of the reformulated problem.
[out]	err	Zero if no error is encountered, nonzero otherwise.

Returns: Solution of original problem.

Implemented in Minotaur::QuadTransformer, Minotaur::SimpleTransformer, and Minotaur::TransPoly.

◆ getSolTrans()

virtual SolutionPtr Minotaur::Transformer::getSolTrans	(	ConstSolutionPtr	sol,
		int &	err
	)

pure virtual

Translate the solution of originial problem into that of reformulated problem.

Parameters

[in]	sol	Solution of the original problem.
[out]	err	Zero if no error is encountered, nonzero otherwise.

Returns: Solution of the reformulated problem.

Implemented in Minotaur::QuadTransformer, Minotaur::SimpleTransformer, and Minotaur::TransPoly.

◆ makeObjLin_()

void Transformer::makeObjLin_ ( )

protectedvirtual

Converts the new Problem newp_ into one with a linear objective by adding a new variable if necessary.

◆ newVar_() [1/3]

VariablePtr Transformer::newVar_	(	CGraphPtr	cg,
		ProblemPtr	newp
	)

protected

Find the auxiliary variable associated with $y_i = f(x)+d$ or create a new one.

Parameters

[in]	The	nonlinear function.
[in]	newp	The transformed problem to which the new constraint should be added, in case this constraint is not found.

Returns: The variable . If the constraint is found, it returns the variable found in it, otherwise it addes a new variable to the problem and returns it.

◆ newVar_() [2/3]

VariablePtr Transformer::newVar_	(	LinearFunctionPtr	lf,
		double	d,
		ProblemPtr	newp
	)

protected

Find the auxiliary variable associated with $y_i = c^Tx+d$ or create a new one.

Parameters

	[in/out]	lf The linear function . If a new variable is created, it is also subtracted from lf.
[in]	d	The value .
[in]	newp	The transformed problem to which the new constraint should be added, in case this constraint is not found.

Returns: The variable . If the constraint is found, it returns the variable found in it, otherwise it addes a new variable to the problem and returns it.

◆ newVar_() [3/3]

VariablePtr Transformer::newVar_	(	VariablePtr	iv,
		double	d,
		ProblemPtr	newp
	)

protected

Find the auxiliary variable associated with $y_i = x_j+d$ or create a new one.

Parameters

[in]	iv	The variable .
[in]	d	The value .
[in]	newp	The transformed problem to which the new constraint should be added, in case this constraint is not found.

Returns: The variable . If the constraint is found, it returns the variable found in it, otherwise it addes a new variable to the problem and returns it.

◆ reformulate()

virtual void Minotaur::Transformer::reformulate	(	ProblemPtr &	newp,
		HandlerVector &	handlers,
		int &	status
	)

pure virtual

Perform the reformulation, and assign handlers.

Parameters

[out]	newp	The new, reformulated problem.
[out]	handlers	A vector of handlers used to reformulate the problem.
[out]	status	Zero if reformulated successfully. Nonzero otherwise.

Implemented in Minotaur::QuadTransformer, Minotaur::SimpleTransformer, and Minotaur::TransPoly.

The documentation for this class was generated from the following files:

/home/amahajan/tmp/minotaur-test/src/base/Transformer.h
/home/amahajan/tmp/minotaur-test/src/base/Transformer.cpp

Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Member Function Documentation

◆ allConsAssigned_()

◆ assignHandler_()

◆ clearUnusedHandlers_()

◆ copyLinear_()

◆ copyVars_()

◆ getName()

◆ getSolOrig()

◆ getSolTrans()

◆ makeObjLin_()

◆ newVar_() [1/3]

◆ newVar_() [2/3]

◆ newVar_() [3/3]

◆ reformulate()