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/********************* */
/*! \file candidate.h
** \verbatim
** Top contributors (to current version):
** Gereon Kremer
** 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 Represents a contraction candidate for ICP-style propagation.
**/
#ifndef CVC4__THEORY__ARITH__ICP__CANDIDATE_H
#define CVC4__THEORY__ARITH__ICP__CANDIDATE_H
#include "cvc4_private.h"
#ifdef CVC4_POLY_IMP
#include <poly/polyxx.h>
#include "expr/node.h"
#include "theory/arith/nl/icp/intersection.h"
namespace CVC4 {
namespace theory {
namespace arith {
namespace nl {
namespace icp {
/**
* A contraction candidate for ICP-style propagation with the following
* semantics:
*
* lhs ~rel~ rhsmult*rhs
*
* where lhs is the variable whose interval we aim to contract, rel is a
* relation symbol (other than disequality), rhsmult is a fractional constant
* and rhs a polynomial. As poly::Polynomial only holds integer polynomials,
* rhsmult is necessary to encode polynomials with rational coefficients.
*
* Additionally, we store the origin of this constraints (a single theory
* constraint) and the variables contained in rhs.
*
* A candidate is evaluated (or propagated) by evaluating the rhsmult*rhs over
* an interval assignment and then updating the interval assignment for lhs with
* the result of this evaluation, properly considering the relation.
*/
struct Candidate
{
/** The target variable */
poly::Variable lhs;
/** The relation symbol */
poly::SignCondition rel;
/** The (integer) polynomial on the right hand side */
poly::Polynomial rhs;
/** The rational multiplier */
poly::Rational rhsmult;
/** The origin of this candidate */
Node origin;
/** The variable within rhs */
std::vector<Node> rhsVariables;
/**
* Contract the interval assignment based on this candidate.
* Only contract if the new interval is below the given threshold, see
* intersect_interval_with().
*/
PropagationResult propagate(poly::IntervalAssignment& ia,
std::size_t size_threshold) const;
};
/** Print a candidate. */
std::ostream& operator<<(std::ostream& os, const Candidate& c);
} // namespace icp
} // namespace nl
} // namespace arith
} // namespace theory
} // namespace CVC4
#endif
#endif
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