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/********************* */
/*! \file optimization_solver.h
** \verbatim
** Top contributors (to current version):
** Michael Chang
** This file is part of the CVC4 project.
** Copyright (c) 2009-2021 by the authors listed in the file AUTHORS
** in the top-level source directory and their institutional affiliations.
** All rights reserved. See the file COPYING in the top-level source
** directory for licensing information.\endverbatim
**
** \brief The solver for optimization queries
**/
#include "cvc4_private.h"
#ifndef CVC4__SMT__OPTIMIZATION_SOLVER_H
#define CVC4__SMT__OPTIMIZATION_SOLVER_H
#include "expr/node.h"
#include "expr/type_node.h"
#include "smt/assertions.h"
#include "util/result.h"
namespace CVC4 {
class SmtEngine;
namespace smt {
/**
* An enum for optimization queries.
*
* Represents whether an objective should be minimized or maximized
*/
enum ObjectiveType
{
OBJECTIVE_MINIMIZE,
OBJECTIVE_MAXIMIZE,
OBJECTIVE_UNDEFINED
};
/**
* An enum for optimization queries.
*
* Represents the result of a checkopt query
* (unimplemented) OPT_OPTIMAL: if value was found
*/
enum OptResult
{
// the original set of assertions has result UNKNOWN
OPT_UNKNOWN,
// the original set of assertions has result UNSAT
OPT_UNSAT,
// the optimization loop finished and optimal
OPT_OPTIMAL,
// The last value is here as a preparation for future work
// in which pproximate optimizations will be supported.
// if the solver halted early and value is only approximate
OPT_SAT_APPROX
};
class Objective
{
public:
Objective(Node n, ObjectiveType type);
~Objective(){};
/** A getter for d_type **/
ObjectiveType getType();
/** A getter for d_node **/
Node getNode();
private:
/** The type of objective this is, either OBJECTIVE_MAXIMIZE OR
* OBJECTIVE_MINIMIZE **/
ObjectiveType d_type;
/** The node associated to the term that was used to construct the objective.
* **/
Node d_node;
};
/**
* A solver for optimization queries.
*
* This class is responsible for responding to optmization queries. It
* spawns a subsolver SmtEngine that captures the parent assertions and
* implements a linear optimization loop. Supports activateObjective,
* checkOpt, and objectiveGetValue in that order.
*/
class OptimizationSolver
{
public:
/** parent is the smt_solver that the user added their assertions to **/
OptimizationSolver(SmtEngine* parent);
~OptimizationSolver();
/** Runs the optimization loop for the activated objective **/
OptResult checkOpt();
/** Activates an objective: will be optimized for **/
void activateObj(const Node& obj, const int& type);
/** Gets the value of the optimized objective after checkopt is called **/
Node objectiveGetValue();
private:
/** The parent SMT engine **/
SmtEngine* d_parent;
/** The objectives to optimize for **/
Objective d_activatedObjective;
/** A saved value of the objective from the last sat call. **/
Node d_savedValue;
};
} // namespace smt
} // namespace CVC4
#endif /* CVC4__SMT__OPTIMIZATION_SOLVER_H */
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