/******************************************************************************

 * Top contributors (to current version):

 *   Tim King, Morgan Deters, Mathias Preiner

 *

 * This file is part of the cvc5 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.

 * ****************************************************************************

 *

 * This is an implementation of the Simplex Module for the Simplex for

 * DPLL(T)decision procedure.

 *

 * This implements the Simplex module for the Simpelx for DPLL(T) decision

 * procedure.

 * See the Simplex for DPLL(T) technical report for more background.(citation?)

 * This shares with the theory a Tableau, and a PartialModel that:

 *  - satisfies the equalities in the Tableau, and

 *  - the assignment for the non-basic variables satisfies their bounds.

 * This is required to either produce a conflict or satisifying PartialModel.

 * Further, we require being told when a basic variable updates its value.

 *

 * During the Simplex search we maintain a queue of variables.

 * The queue is required to contain all of the basic variables that voilate

 * their bounds.

 * As elimination from the queue is more efficient to be done lazily,

 * we do not maintain that the queue of variables needs to be only basic

 * variables or only variables that satisfy their bounds.

 *

 * The simplex procedure roughly follows Alberto's thesis. (citation?)

 * There is one round of selecting using a heuristic pivoting rule.

 * (See PreferenceFunction Documentation for the available options.)

 * The non-basic variable is the one that appears in the fewest pivots.

 * (Bruno says that Leonardo invented this first.)

 * After this, Bland's pivot rule is invoked.

 *

 * During this proccess, we periodically inspect the queue of variables to

 * 1) remove now extraneous extries,

 * 2) detect conflicts that are "waiting" on the queue but may not be detected

 *    by the current queue heuristics, and

 * 3) detect multiple conflicts.

 *

 * Conflicts are greedily slackened to use the weakest bounds that still

 * produce the conflict.

 *

 * Extra things tracked atm: (Subject to change at Tim's whims)

 * - A superset of all of the newly pivoted variables.

 * - A queue of additional conflicts that were discovered by Simplex.

 *   These are theory valid and are currently turned into lemmas

 */

#include "cvc5_private.h"

#pragma once

#include "theory/arith/error_set.h"

#include "theory/arith/linear_equality.h"

#include "theory/arith/simplex.h"

#include "theory/arith/simplex_update.h"

#include "util/dense_map.h"

#include "util/statistics_stats.h"

namespace cvc5 {

namespace theory {

namespace arith {

public:

  FCSimplexDecisionProcedure(LinearEqualityModule& linEq, ErrorSet& errors, RaiseConflict conflictChannel, TempVarMalloc tvmalloc);

  Result::Sat findModel(bool exactResult) override;

  // other error variables are dropping

  WitnessImprovement dualLikeImproveError(ArithVar evar);

  WitnessImprovement primalImproveError(ArithVar evar);

  // dual like

  // - found conflict

  // - satisfied error set

  Result::Sat dualLike();

private:

  static const uint32_t PENALTY = 4;

  DenseMultiset d_scores;

      }

    }else{

    }

  /** The size of the focus set. */

  uint32_t d_focusSize;

  /** The current error focus variable. */

  ArithVar d_focusErrorVar;

  /**

   * The signs of the coefficients in the focus set.

   * This is empty until this has been loaded.

   */

  DenseMap<const Rational*> d_focusCoefficients;

  /**

   * Loads the signs of the coefficients of the variables on the row d_focusErrorVar

   * into d_focusSgns.

   */

  void loadFocusSigns();

  /** Unloads the information from d_focusSgns. */

  void unloadFocusSigns();

  /**

   * The signs of a variable in the row of d_focusErrorVar.

   * d_focusSgns must be loaded.

   */

  const Rational& focusCoefficient(ArithVar nb) const;

  int32_t d_pivotBudget;

  // enum PivotImprovement {

  //   ErrorDropped,

  //   NonDegenerate,

  //   HeuristicDegenerate,

  //   BlandsDegenerate

  // };

  WitnessImprovement d_prevWitnessImprovement;

  uint32_t d_witnessImprovementInARow;

  uint32_t degeneratePivotsInARow() const;

  static const uint32_t s_focusThreshold = 6;

  static const uint32_t s_maxDegeneratePivotsBeforeBlandsOnLeaving = 100;

  static const uint32_t s_maxDegeneratePivotsBeforeBlandsOnEntering = 10;

  DenseMap<uint32_t> d_leavingCountSinceImprovement;

    }else{

    }

    } else {

    }

  }

  bool debugDualLike(WitnessImprovement w, std::ostream& out,

                     int instance,

                     uint32_t prevFocusSize, uint32_t prevErrorSize) const;

  void debugPrintSignal(ArithVar updated) const;

  ArithVarVec d_sgnDisagreements;

  //static PivotImprovement pivotImprovement(const UpdateInfo& selected, bool useBlands = false);

  void logPivot(WitnessImprovement w);

  void updateAndSignal(const UpdateInfo& selected, WitnessImprovement w);

  UpdateInfo selectPrimalUpdate(ArithVar error,

                                LinearEqualityModule::UpdatePreferenceFunction upf,

                                LinearEqualityModule::VarPreferenceFunction bpf);

      &LinearEqualityModule::preferWitness<true>;

      &LinearEqualityModule::minVarOrder;

  }

    LinearEqualityModule::UpdatePreferenceFunction upf;

    } else {

    }

      &LinearEqualityModule::minVarOrder :

      &LinearEqualityModule::minRowLength;

  }

  WitnessImprovement selectFocusImproving() ;

  WitnessImprovement focusUsingSignDisagreements(ArithVar basic);

  WitnessImprovement focusDownToLastHalf();

  WitnessImprovement adjustFocusShrank(const ArithVarVec& drop);

  WitnessImprovement focusDownToJust(ArithVar v);

  void adjustFocusAndError(const UpdateInfo& up, const AVIntPairVec& focusChanges);

  /**

   * This is the main simplex for DPLL(T) loop.

   * It runs for at most maxIterations.

   *

   * Returns true iff it has found a conflict.

   * d_conflictVariable will be set and the conflict for this row is reported.

   */

  bool searchForFeasibleSolution(uint32_t maxIterations);

  }

  static bool debugCheckWitness(const UpdateInfo& inf, WitnessImprovement w, bool useBlands);

  /** These fields are designed to be accessible to TheoryArith methods. */

  public:

    TimerStat d_initialSignalsTime;

    IntStat d_initialConflicts;

    IntStat d_fcFoundUnsat;

    IntStat d_fcFoundSat;

    IntStat d_fcMissed;

    TimerStat d_fcTimer;

    TimerStat d_fcFocusConstructionTimer;

    TimerStat d_selectUpdateForDualLike;

    TimerStat d_selectUpdateForPrimal;

    ReferenceStat<uint32_t> d_finalCheckPivotCounter;

    Statistics(const std::string& name, uint32_t& pivots);

  } d_statistics;

};/* class FCSimplexDecisionProcedure */

}  // namespace arith

}  // namespace theory

}  // namespace cvc5