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#include "cvc4_private.h"
#pragma once
#include "util/statistics_registry.h"
#include "theory/arith/arithvar.h"
#include "theory/arith/linear_equality.h"
#include "util/dense_map.h"
#include <vector>
namespace CVC4 {
namespace theory {
namespace arith {
class ApproximateSimplex{
protected:
int d_pivotLimit;
public:
static bool enabled();
/**
* If glpk is enabled, return a subclass that can do something.
* If glpk is disabled, return a sublass that does nothing.
*/
static ApproximateSimplex* mkApproximateSimplexSolver(const ArithVariables& vars);
ApproximateSimplex();
virtual ~ApproximateSimplex(){}
/** A result is either sat, unsat or unknown.*/
enum ApproxResult {ApproxError, ApproxSat, ApproxUnsat};
struct Solution {
DenseSet newBasis;
DenseMap<DeltaRational> newValues;
Solution() : newBasis(), newValues(){}
};
/** Sets a deterministic effort limit. */
void setPivotLimit(int pivotLimit);
/** Sets a maximization criteria for the approximate solver.*/
virtual void setOptCoeffs(const ArithRatPairVec& ref) = 0;
virtual ApproxResult solveRelaxation() = 0;
virtual Solution extractRelaxation() const = 0;
virtual ApproxResult solveMIP() = 0;
virtual Solution extractMIP() const = 0;
static void applySolution(LinearEqualityModule& linEq, const Solution& sol){
linEq.forceNewBasis(sol.newBasis);
linEq.updateMany(sol.newValues);
}
/** UTILIES FOR DEALING WITH ESTIMATES */
static const double SMALL_FIXED_DELTA;
static const double TOLERENCE;
/** Returns true if two doubles are roughly equal based on TOLERENCE and SMALL_FIXED_DELTA.*/
static bool roughlyEqual(double a, double b);
/**
* Estimates a double as a Rational using continued fraction expansion that
* cuts off the estimate once the value is approximately zero.
* This is designed for removing rounding artifacts.
*/
static Rational estimateWithCFE(double d);
/**
* Converts a rational to a continued fraction expansion representation
* using a maximum number of expansions equal to depth as long as the expression
* is not roughlyEqual() to 0.
*/
static std::vector<Integer> rationalToCfe(const Rational& q, int depth);
/** Converts a continued fraction expansion representation to a rational. */
static Rational cfeToRational(const std::vector<Integer>& exp);
/** Estimates a rational as a continued fraction expansion.*/
static Rational estimateWithCFE(const Rational& q, int depth);
};/* class ApproximateSimplex */
}/* CVC4::theory::arith namespace */
}/* CVC4::theory namespace */
}/* CVC4 namespace */
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