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GCC Code Coverage Report
Directory:	.		Exec	Total	Coverage
File:	src/theory/quantifiers/sygus/sygus_enumerator.cpp	Lines:	627	645	97.2 %
Date:	2021-11-06	Branches:	991	2260	43.8 %

/******************************************************************************
 * Top contributors (to current version):
 *   Andrew Reynolds, Mathias Preiner, Aina Niemetz
 *
 * 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.
 * ****************************************************************************
 *
 * Implementation of sygus_enumerator.
 */

#include "theory/quantifiers/sygus/sygus_enumerator.h"

#include "expr/dtype_cons.h"
#include "expr/node_algorithm.h"
#include "options/datatypes_options.h"
#include "options/quantifiers_options.h"
#include "smt/logic_exception.h"
#include "theory/datatypes/sygus_datatype_utils.h"
#include "theory/datatypes/theory_datatypes_utils.h"
#include "theory/quantifiers/sygus/synth_engine.h"
#include "theory/quantifiers/sygus/type_node_id_trie.h"
#include "theory/rewriter.h"
#include "util/rational.h"

using namespace cvc5::kind;

namespace cvc5 {
namespace theory {
namespace quantifiers {

SygusEnumerator::SygusEnumerator(TermDbSygus* tds,
                                 SygusEnumeratorCallback* sec,
                                 SygusStatistics* s,
                                 bool enumShapes,
                                 bool enumAnyConstHoles)
    : d_tds(tds),
      d_sec(sec),
      d_stats(s),
      d_enumShapes(enumShapes),
      d_enumAnyConstHoles(enumAnyConstHoles),
      d_tlEnum(nullptr),
      d_abortSize(-1)
{
}

void SygusEnumerator::initialize(Node e)
{
  Trace("sygus-enum") << "SygusEnumerator::initialize " << e << std::endl;
  d_enum = e;
  // allocate the default callback
  if (d_sec == nullptr && options::sygusSymBreakDynamic())
  {
    d_secd.reset(new SygusEnumeratorCallbackDefault(e, d_stats));
    d_sec = d_secd.get();
  }
  d_etype = d_enum.getType();
  Assert(d_etype.isDatatype());
  Assert(d_etype.getDType().isSygus());
  d_tlEnum = getMasterEnumForType(d_etype);
  d_abortSize = options::sygusAbortSize();

  // if we don't have a term database, we don't register symmetry breaking
  // lemmas
  if (d_tds == nullptr)
  {
    return;
  }
  // Get the statically registered symmetry breaking clauses for e, see if they
  // can be used for speeding up the enumeration.
  NodeManager* nm = NodeManager::currentNM();
  std::vector<Node> sbl;
  d_tds->getSymBreakLemmas(e, sbl);
  Node ag = d_tds->getActiveGuardForEnumerator(e);
  Node truen = nm->mkConst(true);
  // use TNode for substitute below
  TNode agt = ag;
  TNode truent = truen;
  Assert(d_tcache.find(d_etype) != d_tcache.end());
  const DType& dt = d_etype.getDType();
  for (const Node& lem : sbl)
  {
    if (!d_tds->isSymBreakLemmaTemplate(lem))
    {
      // substitute its active guard by true and rewrite
      Node slem = lem.substitute(agt, truent);
      slem = Rewriter::rewrite(slem);
      // break into conjuncts
      std::vector<Node> sblc;
      if (slem.getKind() == AND)
      {
        for (const Node& slemc : slem)
        {
          sblc.push_back(slemc);
        }
      }
      else
      {
        sblc.push_back(slem);
      }
      for (const Node& sblemma : sblc)
      {
        Trace("sygus-enum")
            << "  symmetry breaking lemma : " << sblemma << std::endl;
        // if its a negation of a unit top-level tester, then this specifies
        // that we should not enumerate terms whose top symbol is that
        // constructor
        if (sblemma.getKind() == NOT)
        {
          Node a;
          int tst = datatypes::utils::isTester(sblemma[0], a);
          if (tst >= 0)
          {
            if (a == e)
            {
              Node cons = dt[tst].getConstructor();
              Trace("sygus-enum") << "  ...unit exclude constructor #" << tst
                                  << ", constructor " << cons << std::endl;
              d_sbExcTlCons.insert(cons);
            }
          }
        }
        // other symmetry breaking lemmas such as disjunctions are not used
      }
    }
  }
}

void SygusEnumerator::addValue(Node v)
{
  // do nothing
}

bool SygusEnumerator::increment() { return d_tlEnum->increment(); }
Node SygusEnumerator::getCurrent()
{
  if (d_abortSize >= 0)
  {
    int cs = static_cast<int>(d_tlEnum->getCurrentSize());
    if (cs > d_abortSize)
    {
      std::stringstream ss;
      ss << "Maximum term size (" << options::sygusAbortSize()
         << ") for enumerative SyGuS exceeded.";
      throw LogicException(ss.str());
    }
  }
  Node ret = d_tlEnum->getCurrent();
  if (!ret.isNull() && !d_sbExcTlCons.empty())
  {
    Assert(ret.hasOperator());
    // might be excluded by an externally provided symmetry breaking clause
    if (d_sbExcTlCons.find(ret.getOperator()) != d_sbExcTlCons.end())
    {
      Trace("sygus-enum-exc")
          << "Exclude (external) : " << datatypes::utils::sygusToBuiltin(ret)
          << std::endl;
      ret = Node::null();
    }
  }
  if (Trace.isOn("sygus-enum"))
  {
    Trace("sygus-enum") << "Enumerate : ";
    TermDbSygus::toStreamSygus("sygus-enum", ret);
    Trace("sygus-enum") << std::endl;
  }
  return ret;
}

bool SygusEnumerator::isEnumShapes() const { return d_enumShapes; }

SygusEnumerator::TermCache::TermCache()
    : d_sec(nullptr),
      d_isSygusType(false),
      d_numConClasses(0),
      d_sizeEnum(0),
      d_isComplete(false)
{
}

void SygusEnumerator::TermCache::initialize(SygusStatistics* s,
                                            Node e,
                                            TypeNode tn,
                                            SygusEnumeratorCallback* sec)
{
  Trace("sygus-enum-debug") << "Init term cache " << tn << "..." << std::endl;
  d_stats = s;
  d_enum = e;
  d_tn = tn;
  d_sec = sec;
  d_sizeStartIndex[0] = 0;
  d_isSygusType = false;

  // compute static information about tn
  if (!d_tn.isDatatype())
  {
    // not a datatype, finish
    return;
  }
  const DType& dt = tn.getDType();
  if (!dt.isSygus())
  {
    // not a sygus datatype, finish
    return;
  }

  d_isSygusType = true;

  // get argument types for all constructors
  std::map<unsigned, std::vector<TypeNode>> argTypes;
  // map weights to constructors
  std::map<unsigned, std::vector<unsigned>> weightsToIndices;

  // constructor class 0 is reserved for nullary operators with 0 weight
  // this is an optimization so that we always skip them for sizes >= 1
  ConstructorClass& ccZero = d_cclass[0];
  ccZero.d_weight = 0;
  d_numConClasses = 1;
  // we must indicate that we should process zero weight constructor classes
  weightsToIndices[0].clear();
  for (unsigned i = 0, ncons = dt.getNumConstructors(); i < ncons; i++)
  {
    // record weight information
    unsigned w = dt[i].getWeight();
    Trace("sygus-enum-debug") << "Weight " << dt[i].getSygusOp() << ": " << w
                              << std::endl;
    weightsToIndices[w].push_back(i);
    // record type information
    for (unsigned j = 0, nargs = dt[i].getNumArgs(); j < nargs; j++)
    {
      TypeNode type = dt[i].getArgType(j);
      argTypes[i].push_back(type);
    }
  }
  NodeManager* nm = NodeManager::currentNM();
  for (std::pair<const unsigned, std::vector<unsigned>>& wp : weightsToIndices)
  {
    unsigned w = wp.first;

    // assign constructors to constructor classes
    TypeNodeIdTrie tnit;
    std::map<Node, unsigned> nToC;
    for (unsigned i : wp.second)
    {
      if (argTypes[i].empty() && w == 0)
      {
        ccZero.d_cons.push_back(i);
      }
      else
      {
        // we merge those whose argument types are the same
        // We could, but choose not to, order these types, which would lead to
        // more aggressive merging of constructor classes. On the negative side,
        // this adds another level of indirection to remember which argument
        // positions the argument types occur in, for each constructor.
        Node n = nm->mkConst(Rational(i));
        nToC[n] = i;
        tnit.add(n, argTypes[i]);
      }
    }
    std::map<Node, unsigned> assign;
    tnit.assignIds(assign, d_numConClasses);
    for (std::pair<const Node, unsigned>& cp : assign)
    {
      // determine which constructor class this goes into using tnit
      unsigned cclassi = cp.second;
      unsigned i = nToC[cp.first];
      Trace("sygus-enum-debug") << "Constructor class for "
                                << dt[i].getSygusOp() << " is " << cclassi
                                << std::endl;
      // initialize the constructor class
      if (d_cclass.find(cclassi) == d_cclass.end())
      {
        d_cclass[cclassi].d_weight = w;
        d_cclass[cclassi].d_types.insert(d_cclass[cclassi].d_types.end(),
                                         argTypes[i].begin(),
                                         argTypes[i].end());
      }
      // add to constructor class
      d_cclass[cclassi].d_cons.push_back(i);
    }
    Trace("sygus-enum-debug") << "#cons classes for weight <= " << w << " : "
                              << d_numConClasses << std::endl;
    d_weightToCcIndex[w] = d_numConClasses;
  }
  Trace("sygus-enum-debug") << "...finish" << std::endl;
}

unsigned SygusEnumerator::TermCache::getLastConstructorClassIndexForWeight(
    unsigned w) const
{
  std::map<unsigned, unsigned>::const_iterator it = d_weightToCcIndex.find(w);
  if (it == d_weightToCcIndex.end())
  {
    return d_numConClasses;
  }
  return it->second;
}
unsigned SygusEnumerator::TermCache::getNumConstructorClasses() const
{
  return d_numConClasses;
}
void SygusEnumerator::TermCache::getConstructorClass(
    unsigned i, std::vector<unsigned>& cclass) const
{
  std::map<unsigned, ConstructorClass>::const_iterator it = d_cclass.find(i);
  Assert(it != d_cclass.end());
  cclass.insert(
      cclass.end(), it->second.d_cons.begin(), it->second.d_cons.end());
}
void SygusEnumerator::TermCache::getTypesForConstructorClass(
    unsigned i, std::vector<TypeNode>& types) const
{
  std::map<unsigned, ConstructorClass>::const_iterator it = d_cclass.find(i);
  Assert(it != d_cclass.end());
  types.insert(
      types.end(), it->second.d_types.begin(), it->second.d_types.end());
}

unsigned SygusEnumerator::TermCache::getWeightForConstructorClass(
    unsigned i) const
{
  std::map<unsigned, ConstructorClass>::const_iterator it = d_cclass.find(i);
  Assert(it != d_cclass.end());
  return it->second.d_weight;
}

bool SygusEnumerator::TermCache::addTerm(Node n)
{
  if (!d_isSygusType)
  {
    // non-sygus terms generated by TermEnumMasterInterp/TermEnumMasterFv
    // enumeration are unique by construction
    Trace("sygus-enum-terms") << "tc(" << d_tn << "): term (builtin): " << n
                              << std::endl;
    d_terms.push_back(n);
    return true;
  }
  Assert(!n.isNull());
  if (d_sec != nullptr)
  {
    if (!d_sec->addTerm(n, d_bterms))
    {
      Trace("sygus-enum-exc")
          << "Exclude: " << datatypes::utils::sygusToBuiltin(n)
          << " due to callback" << std::endl;
      return false;
    }
  }
  if (d_stats != nullptr)
  {
    ++(d_stats->d_enumTerms);
  }
  d_terms.push_back(n);
  return true;
}
void SygusEnumerator::TermCache::pushEnumSizeIndex()
{
  d_sizeEnum++;
  d_sizeStartIndex[d_sizeEnum] = d_terms.size();
  Trace("sygus-enum-debug") << "tc(" << d_tn << "): size " << d_sizeEnum
                            << " terms start at index " << d_terms.size()
                            << std::endl;
}
unsigned SygusEnumerator::TermCache::getEnumSize() const { return d_sizeEnum; }
unsigned SygusEnumerator::TermCache::getIndexForSize(unsigned s) const
{
  Assert(s <= d_sizeEnum);
  std::map<unsigned, unsigned>::const_iterator it = d_sizeStartIndex.find(s);
  Assert(it != d_sizeStartIndex.end());
  return it->second;
}
Node SygusEnumerator::TermCache::getTerm(unsigned index) const
{
  Assert(index < d_terms.size());
  return d_terms[index];
}

unsigned SygusEnumerator::TermCache::getNumTerms() const
{
  return d_terms.size();
}

bool SygusEnumerator::TermCache::isComplete() const { return d_isComplete; }
void SygusEnumerator::TermCache::setComplete() { d_isComplete = true; }
unsigned SygusEnumerator::TermEnum::getCurrentSize() { return d_currSize; }
SygusEnumerator::TermEnum::TermEnum() : d_se(nullptr), d_currSize(0) {}
SygusEnumerator::TermEnumSlave::TermEnumSlave()
    : TermEnum(),
      d_sizeLim(0),
      d_index(0),
      d_indexNextEnd(0),
      d_hasIndexNextEnd(false),
      d_master(nullptr)
{
}

bool SygusEnumerator::TermEnumSlave::initialize(SygusEnumerator* se,
                                                TypeNode tn,
                                                unsigned sizeMin,
                                                unsigned sizeMax)
{
  d_se = se;
  d_tn = tn;
  d_sizeLim = sizeMax;
  Trace("sygus-enum-debug2") << "slave(" << d_tn
                             << "): init, min/max=" << sizeMin << "/" << sizeMax
                             << "...\n";

  // must have pointer to the master
  d_master = d_se->getMasterEnumForType(d_tn);

  SygusEnumerator::TermCache& tc = d_se->d_tcache[d_tn];
  // if the size is exact, we start at the limit
  d_currSize = sizeMin;
  // initialize the index
  while (d_currSize > tc.getEnumSize())
  {
    Trace("sygus-enum-debug2") << "slave(" << d_tn
                               << "): init force increment master...\n";
    // increment the master until we have enough terms
    if (!d_master->increment())
    {
      Trace("sygus-enum-debug2") << "slave(" << d_tn
                                 << "): ...fail init force master\n";
      return false;
    }
    Trace("sygus-enum-debug2") << "slave(" << d_tn
                               << "): ...success init force master\n";
  }
  d_index = tc.getIndexForSize(d_currSize);
  Trace("sygus-enum-debug2") << "slave(" << d_tn << "): validate indices...\n";
  // initialize the next end index (marks where size increments)
  validateIndexNextEnd();
  Trace("sygus-enum-debug2")
      << "slave(" << d_tn << "): validate init end: " << d_hasIndexNextEnd
      << " " << d_indexNextEnd << " " << d_index << " " << d_currSize << "\n";
  // ensure that indexNextEnd is valid (it must be greater than d_index)
  bool ret = validateIndex();
  Trace("sygus-enum-debug2")
      << "slave(" << d_tn << "): ..." << (ret ? "success" : "fail")
      << " init, now: " << d_hasIndexNextEnd << " " << d_indexNextEnd << " "
      << d_index << " " << d_currSize << "\n";
  return ret;
}

Node SygusEnumerator::TermEnumSlave::getCurrent()
{
  SygusEnumerator::TermCache& tc = d_se->d_tcache[d_tn];
  Node curr = tc.getTerm(d_index);
  Trace("sygus-enum-debug2")
      << "slave(" << d_tn
      << "): current : " << datatypes::utils::sygusToBuiltin(curr)
      << ", sizes = " << datatypes::utils::getSygusTermSize(curr) << " "
      << getCurrentSize() << std::endl;
  Trace("sygus-enum-debug2") << "slave(" << d_tn
                             << "): indices : " << d_hasIndexNextEnd << " "
                             << d_indexNextEnd << " " << d_index << std::endl;
  // lookup in the cache
  return tc.getTerm(d_index);
}

bool SygusEnumerator::TermEnumSlave::increment()
{
  // increment index
  d_index++;
  // ensure that index is valid
  return validateIndex();
}

bool SygusEnumerator::TermEnumSlave::validateIndex()
{
  Trace("sygus-enum-debug2") << "slave(" << d_tn << ") : validate index...\n";
  SygusEnumerator::TermCache& tc = d_se->d_tcache[d_tn];
  // ensure that index is in the range
  while (d_index >= tc.getNumTerms())
  {
    Assert(d_index == tc.getNumTerms());
    Trace("sygus-enum-debug2") << "slave(" << d_tn << ") : force master...\n";
    // if the size of the master is larger than the size limit, then
    // there is no use continuing, since there are no more terms that this
    // slave enumerator can return.
    if (d_master->getCurrentSize() > d_sizeLim)
    {
      return false;
    }
    // must push the master index
    if (!d_master->increment())
    {
      Trace("sygus-enum-debug2") << "slave(" << d_tn
                                 << ") : ...fail force master\n";
      return false;
    }
    Trace("sygus-enum-debug2") << "slave(" << d_tn
                               << ") : ...success force master\n";
  }
  // always validate the next index end here
  validateIndexNextEnd();
  Trace("sygus-enum-debug2") << "slave(" << d_tn
                             << ") : validate index end...\n";
  // if we are at the beginning of the next size, increment current size
  while (d_hasIndexNextEnd && d_index == d_indexNextEnd)
  {
    d_currSize++;
    Trace("sygus-enum-debug2") << "slave(" << d_tn << ") : size++ ("
                               << d_currSize << "/" << d_sizeLim << ")\n";
    // if we've hit the size limit, return false
    if (d_currSize > d_sizeLim)
    {
      Trace("sygus-enum-debug2") << "slave(" << d_tn << ") : fail size\n";
      return false;
    }
    validateIndexNextEnd();
  }
  Trace("sygus-enum-debug2") << "slave(" << d_tn << ") : finished\n";
  return true;
}

void SygusEnumerator::TermEnumSlave::validateIndexNextEnd()
{
  SygusEnumerator::TermCache& tc = d_se->d_tcache[d_tn];
  // update the next end index
  d_hasIndexNextEnd = d_currSize < tc.getEnumSize();
  if (d_hasIndexNextEnd)
  {
    d_indexNextEnd = tc.getIndexForSize(d_currSize + 1);
  }
}

void SygusEnumerator::initializeTermCache(TypeNode tn)
{
  // initialize the term cache
  d_tcache[tn].initialize(d_stats, d_enum, tn, d_sec);
}

SygusEnumerator::TermEnum* SygusEnumerator::getMasterEnumForType(TypeNode tn)
{
  if (tn.isDatatype() && tn.getDType().isSygus())
  {
    std::map<TypeNode, TermEnumMaster>::iterator it = d_masterEnum.find(tn);
    if (it != d_masterEnum.end())
    {
      return &it->second;
    }
    initializeTermCache(tn);
    // initialize the master enumerator
    bool ret = d_masterEnum[tn].initialize(this, tn);
    AlwaysAssert(ret);
    return &d_masterEnum[tn];
  }
  if (d_enumAnyConstHoles)
  {
    std::map<TypeNode, TermEnumMasterFv>::iterator it = d_masterEnumFv.find(tn);
    if (it != d_masterEnumFv.end())
    {
      return &it->second;
    }
    initializeTermCache(tn);
    // initialize the master enumerator
    bool ret = d_masterEnumFv[tn].initialize(this, tn);
    AlwaysAssert(ret);
    return &d_masterEnumFv[tn];
  }
  std::map<TypeNode, std::unique_ptr<TermEnumMasterInterp>>::iterator it =
      d_masterEnumInt.find(tn);
  if (it != d_masterEnumInt.end())
  {
    return it->second.get();
  }
  initializeTermCache(tn);
  // create the master enumerator
  d_masterEnumInt[tn].reset(new TermEnumMasterInterp(tn));
  // initialize the master enumerator
  TermEnumMasterInterp* temi = d_masterEnumInt[tn].get();
  bool ret = temi->initialize(this, tn);
  AlwaysAssert(ret);
  return temi;
}

SygusEnumerator::TermEnumMaster::TermEnumMaster()
    : TermEnum(),
      d_enumShapes(false),
      d_enumShapesInit(false),
      d_isIncrementing(false),
      d_currTermSet(false),
      d_consClassNum(0),
      d_ccWeight(0),
      d_consNum(0),
      d_currChildSize(0),
      d_childrenValid(0)
{
}

bool SygusEnumerator::TermEnumMaster::initialize(SygusEnumerator* se,
                                                 TypeNode tn)
{
  Trace("sygus-enum-debug") << "master(" << tn << "): init...\n";
  d_tds = se->d_tds;
  d_se = se;
  d_tn = tn;

  d_currSize = 0;
  // we will start with constructor class zero
  d_consClassNum = 0;
  d_currChildSize = 0;
  d_ccCons.clear();
  d_enumShapes = se->isEnumShapes();
  d_enumShapesInit = false;
  d_isIncrementing = false;
  d_currTermSet = false;
  bool ret = increment();
  Trace("sygus-enum-debug") << "master(" << tn
                            << "): finish init, ret = " << ret << "\n";
  return ret;
}

Node SygusEnumerator::TermEnumMaster::getCurrent()
{
  if (d_currTermSet)
  {
    return d_currTerm;
  }
  d_currTermSet = true;
  // construct based on the children
  std::vector<Node> children;
  const DType& dt = d_tn.getDType();
  Assert(d_consNum > 0 && d_consNum <= d_ccCons.size());
  // get the current constructor number
  unsigned cnum = d_ccCons[d_consNum - 1];
  children.push_back(dt[cnum].getConstructor());
  // add the current of each child to children
  for (unsigned i = 0, nargs = dt[cnum].getNumArgs(); i < nargs; i++)
  {
    Assert(d_children.find(i) != d_children.end());
    Node cc = d_children[i].getCurrent();
    if (cc.isNull())
    {
      d_currTerm = cc;
      return cc;
    }
    children.push_back(cc);
  }
  if (d_enumShapes)
  {
    // ensure all variables are unique
    childrenToShape(children);
  }
  d_currTerm = NodeManager::currentNM()->mkNode(APPLY_CONSTRUCTOR, children);
  return d_currTerm;
}

bool SygusEnumerator::TermEnumMaster::increment()
{
  // Am I already incrementing? If so, fail.
  // This is to break infinite loops for slave enumerators who request an
  // increment() from the master enumerator of their type that is also their
  // parent. This ensures we do not loop on a grammar like:
  //   A -> -( A ) | B+B
  //   B -> x | y
  // where we require the first term enumerated to be over B+B.
  // Set that we are incrementing
  if (d_isIncrementing)
  {
    return false;
  }
  Trace("sygus-enum-summary") << "SygusEnumerator::TermEnumMaster: increment "
                              << d_tn << "..." << std::endl;
  d_isIncrementing = true;
  bool ret = incrementInternal();
  d_isIncrementing = false;
  Trace("sygus-enum-summary")
      << "SygusEnumerator::TermEnumMaster: finished increment " << d_tn
      << std::endl;
  return ret;
}

bool SygusEnumerator::TermEnumMaster::incrementInternal()
{
  SygusEnumerator::TermCache& tc = d_se->d_tcache[d_tn];
  if (tc.isComplete())
  {
    return false;
  }
  Trace("sygus-enum-debug2") << "master(" << d_tn
                             << "): get last constructor class..." << std::endl;
  // the maximum index of a constructor class to consider
  unsigned ncc = tc.getLastConstructorClassIndexForWeight(d_currSize);
  Trace("sygus-enum-debug2") << "Last constructor class " << d_currSize << ": "
                             << ncc << std::endl;
  // If we are enumerating shapes, the first enumerated term is a free variable.
  if (d_enumShapes && !d_enumShapesInit)
  {
    Assert(d_tds != nullptr);
    Node fv = d_tds->getFreeVar(d_tn, 0);
    d_enumShapesInit = true;
    d_currTermSet = true;
    d_currTerm = fv;
    // must add to term cache
    tc.addTerm(fv);
    return true;
  }

  // have we initialized the current constructor class?
  while (d_ccCons.empty() && d_consClassNum < ncc)
  {
    Assert(d_ccTypes.empty());
    Trace("sygus-enum-debug2") << "master(" << d_tn
                               << "): try constructor class " << d_consClassNum
                               << std::endl;
    // get the list of constructors in the constructor class
    tc.getConstructorClass(d_consClassNum, d_ccCons);
    // if there are any...
    if (!d_ccCons.empty())
    {
      // successfully initialized the constructor class
      d_consNum = 0;
      // we will populate the children
      Assert(d_children.empty());
      Assert(d_ccTypes.empty());
      tc.getTypesForConstructorClass(d_consClassNum, d_ccTypes);
      d_ccWeight = tc.getWeightForConstructorClass(d_consClassNum);
      d_childrenValid = 0;
      // initialize the children into their initial state
      if (!initializeChildren())
      {
        // didn't work (due to size), we will try the next class
        d_ccCons.clear();
        d_ccTypes.clear();
        Trace("sygus-enum-debug2") << "master(" << d_tn
                                   << "): failed due to init size\n";
      }
    }
    else
    {
      // No constructors in constructor class. This can happen for class 0 if a
      // type has no nullary constructors with weight 0.
      Trace("sygus-enum-debug2") << "master(" << d_tn
                                 << "): failed due to no cons\n";
    }
    // increment the next constructor class we will try
    d_consClassNum++;
  }

  // have we run out of constructor classes for this size?
  if (d_ccCons.empty())
  {
    // check whether we should terminate, which notice always treats
    // uninterpreted sorts as infinite, since we do not put bounds on them
    // in our enumeration.
    if (isCardinalityClassFinite(d_tn.getCardinalityClass(), false))
    {
      if (ncc == tc.getNumConstructorClasses())
      {
        bool doTerminate = true;
        for (unsigned i = 1; i < ncc; i++)
        {
          // The maximum size of terms from a constructor class can be
          // determined if all of its argument types are finished enumerating.
          // If this maximum size is less than or equal to d_currSize for
          // each constructor class, we are done.
          unsigned sum = tc.getWeightForConstructorClass(i);
          std::vector<TypeNode> cctns;
          tc.getTypesForConstructorClass(i, cctns);
          for (unsigned j = 0, ntypes = cctns.size(); j < ntypes; j++)
          {
            TypeNode tnc = cctns[j];
            SygusEnumerator::TermCache& tcc = d_se->d_tcache[tnc];
            if (!tcc.isComplete())
            {
              // maximum size of this constructor class cannot be determined
              doTerminate = false;
              break;
            }
            else
            {
              sum += tcc.getEnumSize();
              if (sum > d_currSize)
              {
                // maximum size of this constructor class is greater than size
                doTerminate = false;
                break;
              }
            }
          }
          if (!doTerminate)
          {
            break;
          }
        }
        if (doTerminate)
        {
          Trace("sygus-engine") << "master(" << d_tn << "): complete at size "
                                << d_currSize << std::endl;
          tc.setComplete();
          return false;
        }
      }
    }

    // increment the size bound
    d_currSize++;
    Trace("sygus-enum-debug2") << "master(" << d_tn
                               << "): size++ : " << d_currSize << "\n";
    if (Trace.isOn("sygus-engine"))
    {
      // am i the master enumerator? if so, print
      if (d_se->d_tlEnum == this)
      {
        Trace("sygus-engine") << "SygusEnumerator::size = " << d_currSize
                              << std::endl;
      }
    }

    // push the bound
    tc.pushEnumSizeIndex();

    // restart with constructor class one (skip nullary constructors)
    d_consClassNum = 1;

    // We break for a round: return the null term when we cross a size
    // boundary. This ensures that the necessary breaks are taken, e.g.
    // in slave enumerators who may instead want to abandon this call to
    // increment master when the size of the master makes their increment
    // infeasible.
    d_currTermSet = true;
    d_currTerm = Node::null();
    return true;
  }

  bool incSuccess = false;
  do
  {
    Trace("sygus-enum-debug2") << "master(" << d_tn << "): check return "
                               << d_childrenValid << "/" << d_ccTypes.size()
                               << std::endl;
    // the children should be initialized by here
    Assert(d_childrenValid == d_ccTypes.size());

    // do we have more constructors for the given children?
    if (d_consNum < d_ccCons.size())
    {
      Trace("sygus-enum-debug2") << "master(" << d_tn << "): try constructor "
                                 << d_consNum << std::endl;
      // increment constructor index
      // we will build for the current constructor and the given children
      d_consNum++;
      d_currTermSet = false;
      d_currTerm = Node::null();
      Node c = getCurrent();
      if (!c.isNull())
      {
        if (!tc.addTerm(c))
        {
          // the term was not unique based on rewriting
          Trace("sygus-enum-debug2") << "master(" << d_tn
                                     << "): failed addTerm\n";
          // we will return null (d_currTermSet is true at this point)
          Assert(d_currTermSet);
          d_currTerm = Node::null();
        }
      }
      return true;
    }

    // finished constructors for this set of children, must increment children

    // reset the constructor number
    d_consNum = 0;

    // try incrementing the last child until we find one that works
    incSuccess = false;
    while (!incSuccess && d_childrenValid > 0)
    {
      Trace("sygus-enum-debug2") << "master(" << d_tn << "): try incrementing "
                                 << d_childrenValid << std::endl;
      unsigned i = d_childrenValid - 1;
      Assert(d_children[i].getCurrentSize() <= d_currChildSize);
      // track the size
      d_currChildSize -= d_children[i].getCurrentSize();
      if (d_children[i].increment())
      {
        Trace("sygus-enum-debug2") << "master(" << d_tn
                                   << "): increment success...\n";
        d_currChildSize += d_children[i].getCurrentSize();
        // must see if we can initialize the remaining children here
        // if not, there is no use continuing.
        if (initializeChildren())
        {
          Trace("sygus-enum-debug2")
              << "master(" << d_tn << "): success init children\n";
          Assert(d_currChildSize + d_ccWeight <= d_currSize);
          incSuccess = true;
        }
        else
        {
          // failed to initialize the remaining children (likely due to a
          // child having a non-zero minimum size bound).
          Trace("sygus-enum-debug2")
              << "master(" << d_tn << "): fail init children\n";
          d_currChildSize -= d_children[i].getCurrentSize();
        }
      }
      if (!incSuccess)
      {
        Trace("sygus-enum-debug2") << "master(" << d_tn
                                   << "): fail, backtrack...\n";
        // current child is out of values
        d_children.erase(i);
        d_childrenValid--;
      }
    }
  } while (incSuccess);
  Trace("sygus-enum-debug2") << "master(" << d_tn
                             << "): failed increment children\n";
  // restart with the next constructor class
  d_ccCons.clear();
  d_ccTypes.clear();
  return incrementInternal();
}

bool SygusEnumerator::TermEnumMaster::initializeChildren()
{
  Trace("sygus-enum-debug2")
      << "master(" << d_tn << "): init children, start = " << d_childrenValid
      << ", #types=" << d_ccTypes.size() << ", sizes=" << d_currChildSize << "/"
      << d_currSize << std::endl;
  unsigned currChildren = d_childrenValid;
  unsigned sizeMin = 0;
  // while we need to initialize the current child
  while (d_childrenValid < d_ccTypes.size())
  {
    if (!initializeChild(d_childrenValid, sizeMin))
    {
      if (d_childrenValid == currChildren)
      {
        // we are back to the child we started with, we terminate now.
        Trace("sygus-enum-debug2") << "master(" << d_tn
                                   << "): init children : failed, finished"
                                   << std::endl;
        return false;
      }
      Trace("sygus-enum-debug2") << "master(" << d_tn
                                 << "): init children : failed" << std::endl;
      // we failed in this size configuration
      // reinitialize with the next size up
      unsigned currSize = d_children[d_childrenValid - 1].getCurrentSize();
      d_currChildSize -= currSize;
      sizeMin = currSize + 1;
      d_children.erase(d_childrenValid - 1);
      d_childrenValid--;
    }
    else
    {
      sizeMin = 0;
      d_childrenValid++;
    }
  }
  Trace("sygus-enum-debug2") << "master(" << d_tn
                             << "): init children : success" << std::endl;
  // initialized all children
  return true;
}

bool SygusEnumerator::TermEnumMaster::initializeChild(unsigned i,
                                                      unsigned sizeMin)
{
  Assert(d_ccWeight <= d_currSize);
  Assert(d_currChildSize + d_ccWeight <= d_currSize);
  unsigned sizeMax = (d_currSize - d_ccWeight) - d_currChildSize;
  Trace("sygus-enum-debug2") << "master(" << d_tn << "): initializeChild " << i
                             << " (" << d_currSize << ", " << d_ccWeight << ", "
                             << d_currChildSize << ")\n";
  if (sizeMin > sizeMax)
  {
    Trace("sygus-enum-debug2") << "master(" << d_tn << "): failed due to size "
                               << sizeMin << "/" << sizeMax << "\n";
    return false;
  }
  // initialize the child to enumerate exactly the terms that sum to size
  sizeMin = (i + 1 == d_ccTypes.size()) ? sizeMax : sizeMin;
  TermEnumSlave& te = d_children[i];
  bool init = te.initialize(d_se, d_ccTypes[i], sizeMin, sizeMax);
  if (!init)
  {
    // failed to initialize
    d_children.erase(i);
    Trace("sygus-enum-debug2") << "master(" << d_tn
                               << "): failed due to child init\n";
    return false;
  }
  unsigned teSize = te.getCurrentSize();
  // fail if the initial children size does not fit d_currSize-d_ccWeight
  if (teSize + d_currChildSize + d_ccWeight > d_currSize)
  {
    d_children.erase(i);
    Trace("sygus-enum-debug2") << "master(" << d_tn
                               << "): failed due to child size\n";
    return false;
  }
  d_currChildSize += teSize;
  Trace("sygus-enum-debug2") << "master(" << d_tn
                             << "): success initializeChild " << i << "\n";
  return true;
}

void SygusEnumerator::TermEnumMaster::childrenToShape(
    std::vector<Node>& children)
{
  if (children.size() <= 2)
  {
    // don't need to convert constants and unary applications
    return;
  }
  std::map<TypeNode, int> vcounter;
  // Buffered child, so that we only compute vcounter if there are more than
  // one children with free variables, since otherwise there is no change.
  // For example, if we are given { C, (+ x1 x2), 1 }, we buffer child (+ x1 x2)
  // noting that it has free variables. We proceed with processing the remaining
  // children, and note that no other child contains free variables, and hence
  // no change is necessary (since by construction, all children have the
  // property of having unique variable subterms). On the other hand if the
  // last child above was x1, then this would trigger us to convert (+ x1 x2)
  // while computing vcounter, and subsequently update x1 to x3 to obtain
  // { C, (+ x1 x2), x3 }.
  // Have we set the buffer child index
  bool bufferChildSet = false;
  // Have we processed the buffer child index
  bool bufferChildProcessed = false;
  // The buffer child index
  size_t bufferChild = 0;
  for (size_t i = 1, nchildren = children.size(); i < nchildren; i++)
  {
    if (!expr::hasBoundVar(children[i]))
    {
      // don't need to care about expressions with no bound variables
      continue;
    }
    else if (!bufferChildSet)
    {
      bufferChild = i;
      bufferChildSet = true;
      continue;
    }
    else if (!bufferChildProcessed)
    {
      // process the buffer child
      children[bufferChild] = convertShape(children[bufferChild], vcounter);
      bufferChildProcessed = true;
    }
    children[i] = convertShape(children[i], vcounter);
  }
}

Node SygusEnumerator::TermEnumMaster::convertShape(
    Node n, std::map<TypeNode, int>& vcounter)
{
  Assert(d_tds != nullptr);
  NodeManager* nm = NodeManager::currentNM();
  std::unordered_map<TNode, Node> visited;
  std::unordered_map<TNode, Node>::iterator it;
  std::vector<TNode> visit;
  TNode cur;
  visit.push_back(n);
  do
  {
    cur = visit.back();
    visit.pop_back();
    it = visited.find(cur);

    if (it == visited.end())
    {
      if (cur.isVar())
      {
        // do the conversion
        visited[cur] = d_tds->getFreeVarInc(cur.getType(), vcounter);
      }
      else if (!expr::hasBoundVar(cur))
      {
        // no bound variables, no change
        visited[cur] = cur;
      }
      else
      {
        visited[cur] = Node::null();
        visit.push_back(cur);
        visit.insert(visit.end(), cur.begin(), cur.end());
      }
    }
    else if (it->second.isNull())
    {
      Node ret = cur;
      bool childChanged = false;
      std::vector<Node> children;
      if (cur.getMetaKind() == metakind::PARAMETERIZED)
      {
        children.push_back(cur.getOperator());
      }
      for (const Node& cn : cur)
      {
        it = visited.find(cn);
        Assert(it != visited.end());
        Assert(!it->second.isNull());
        childChanged = childChanged || cn != it->second;
        children.push_back(it->second);
      }
      if (childChanged)
      {
        ret = nm->mkNode(cur.getKind(), children);
      }
      visited[cur] = ret;
    }
  } while (!visit.empty());
  Assert(visited.find(n) != visited.end());
  Assert(!visited.find(n)->second.isNull());
  return visited[n];
}

SygusEnumerator::TermEnumMasterInterp::TermEnumMasterInterp(TypeNode tn)
    : TermEnum(), d_te(tn), d_currNumConsts(0), d_nextIndexEnd(0)
{
}

bool SygusEnumerator::TermEnumMasterInterp::initialize(SygusEnumerator* se,
                                                       TypeNode tn)
{
  d_se = se;
  d_tn = tn;
  d_currSize = 0;
  d_currNumConsts = 1;
  d_nextIndexEnd = 1;
  return true;
}

Node SygusEnumerator::TermEnumMasterInterp::getCurrent() { return *d_te; }
bool SygusEnumerator::TermEnumMasterInterp::increment()
{
  if (d_te.isFinished())
  {
    return false;
  }
  SygusEnumerator::TermCache& tc = d_se->d_tcache[d_tn];
  Node curr = getCurrent();
  tc.addTerm(curr);
  if (tc.getNumTerms() == d_nextIndexEnd)
  {
    tc.pushEnumSizeIndex();
    d_currSize++;
    d_currNumConsts = d_currNumConsts * options::sygusActiveGenEnumConsts();
    d_nextIndexEnd = d_nextIndexEnd + d_currNumConsts;
  }
  ++d_te;
  return !d_te.isFinished();
}
SygusEnumerator::TermEnumMasterFv::TermEnumMasterFv() : TermEnum() {}
bool SygusEnumerator::TermEnumMasterFv::initialize(SygusEnumerator* se,
                                                   TypeNode tn)
{
  d_se = se;
  d_tn = tn;
  d_currSize = 0;
  Node ret = getCurrent();
  AlwaysAssert(!ret.isNull());
  SygusEnumerator::TermCache& tc = d_se->d_tcache[d_tn];
  tc.addTerm(ret);
  return true;
}

Node SygusEnumerator::TermEnumMasterFv::getCurrent()
{
  Assert(d_se->d_tds != nullptr);
  Node ret = d_se->d_tds->getFreeVar(d_tn, d_currSize);
  Trace("sygus-enum-debug2") << "master_fv(" << d_tn << "): mk " << ret
                             << std::endl;
  return ret;
}

bool SygusEnumerator::TermEnumMasterFv::increment()
{
  SygusEnumerator::TermCache& tc = d_se->d_tcache[d_tn];
  // size increments at a constant rate
  d_currSize++;
  tc.pushEnumSizeIndex();
  Node curr = getCurrent();
  Trace("sygus-enum-debug2") << "master_fv(" << d_tn << "): increment, add "
                             << curr << std::endl;
  bool ret = tc.addTerm(curr);
  AlwaysAssert(ret);
  return true;
}

}  // namespace quantifiers
}  // namespace theory
}  // namespace cvc5

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