mosesdecoder/moses2/HypothesisColl.cpp

/*
 * HypothesisColl.cpp
 *
 *  Created on: 26 Feb 2016
 *      Author: hieu
 */
#include <iostream>
#include <sstream>
#include <algorithm>
#include <boost/foreach.hpp>
#include "HypothesisColl.h"
#include "ManagerBase.h"
#include "System.h"
#include "MemPoolAllocator.h"

using namespace std;

namespace Moses2
{

HypothesisColl::HypothesisColl(const ManagerBase &mgr)
  :m_coll(MemPoolAllocator<const HypothesisBase*>(mgr.GetPool()))
  ,m_sortedHypos(NULL)
{
  m_bestScore = -std::numeric_limits<float>::infinity();
  m_worstScore = std::numeric_limits<float>::infinity();
}

const HypothesisBase *HypothesisColl::GetBestHypo() const
{
  if (GetSize() == 0) {
    return NULL;
  }
  if (m_sortedHypos) {
    return (*m_sortedHypos)[0];
  }

  SCORE bestScore = -std::numeric_limits<SCORE>::infinity();
  const HypothesisBase *bestHypo;
  BOOST_FOREACH(const HypothesisBase *hypo, m_coll) {
    if (hypo->GetFutureScore() > bestScore) {
      bestScore = hypo->GetFutureScore();
      bestHypo = hypo;
    }
  }
  return bestHypo;
}

void HypothesisColl::Add(
  const ManagerBase &mgr,
  HypothesisBase *hypo,
  Recycler<HypothesisBase*> &hypoRecycle,
  ArcLists &arcLists)
{
  size_t maxStackSize = mgr.system.options.search.stack_size;

  if (GetSize() > maxStackSize * 2) {
    //cerr << "maxStackSize=" << maxStackSize << " " << GetSize() << endl;
    PruneHypos(mgr, mgr.arcLists);
  }

  SCORE futureScore = hypo->GetFutureScore();

  /*
  cerr << "scores:"
      << futureScore << " "
      << m_bestScore << " "
      << GetSize() << " "
      << endl;
  */
  if (GetSize() >= maxStackSize && futureScore < m_worstScore) {
    // beam threshold or really bad hypo that won't make the pruning cut
    // as more hypos are added, the m_worstScore stat gets out of date and isn't the optimum cut-off point
    //cerr << "Discard, really bad score:" << hypo->Debug(mgr.system) << endl;
    hypoRecycle.Recycle(hypo);
    return;
  }

  StackAdd added = Add(hypo);

  size_t nbestSize = mgr.system.options.nbest.nbest_size;
  if (nbestSize) {
    arcLists.AddArc(added.added, hypo, added.other);
  } else {
    if (added.added) {
      if (added.other) {
        hypoRecycle.Recycle(added.other);
      }
    } else {
      hypoRecycle.Recycle(hypo);
    }
  }

  // update beam variables
  if (added.added) {
    if (futureScore > m_bestScore) {
      m_bestScore = futureScore;
      float beamWidth = mgr.system.options.search.beam_width;
      if ( m_bestScore + beamWidth > m_worstScore ) {
        m_worstScore = m_bestScore + beamWidth;
      }
    } else if (GetSize() <= maxStackSize && futureScore < m_worstScore) {
      m_worstScore = futureScore;
    }
  }
}

StackAdd HypothesisColl::Add(const HypothesisBase *hypo)
{
  std::pair<_HCType::iterator, bool> addRet = m_coll.insert(hypo);
  //cerr << endl << "new=" << hypo->Debug(hypo->GetManager().system) << endl;

  // CHECK RECOMBINATION
  if (addRet.second) {
    // equiv hypo doesn't exists
    //cerr << "Added " << hypo << endl;
    return StackAdd(true, NULL);
  } else {
    HypothesisBase *hypoExisting = const_cast<HypothesisBase*>(*addRet.first);
    //cerr << "hypoExisting=" << hypoExisting->Debug(hypo->GetManager().system) << endl;

    if (hypo->GetFutureScore() > hypoExisting->GetFutureScore()) {
      // incoming hypo is better than the one we have
  	  //cerr << "Add " << hypo << "(" << hypo->hash() << ")"
	  //	  << " discard existing " << hypoExisting << "(" << hypoExisting->hash() << ")"
	  //	  << endl;

      const HypothesisBase * const &hypoExisting1 = *addRet.first;
      const HypothesisBase *&hypoExisting2 =
        const_cast<const HypothesisBase *&>(hypoExisting1);
      hypoExisting2 = hypo;

      return StackAdd(true, hypoExisting);
    } else {
      // already storing the best hypo. discard incoming hypo
      //cerr << "Keep existing " << hypoExisting << "(" << hypoExisting->hash() << ")"
      //		  << " discard new " << hypo << "(" << hypo->hash() << ")"
	  //		  << endl;
      return StackAdd(false, hypoExisting);
    }
  }

  //assert(false);
}

const Hypotheses &HypothesisColl::GetSortedAndPrunedHypos(
  const ManagerBase &mgr,
  ArcLists &arcLists) const
{
  if (m_sortedHypos == NULL) {
    // create sortedHypos first
    MemPool &pool = mgr.GetPool();
    m_sortedHypos = new (pool.Allocate<Hypotheses>()) Hypotheses(pool,
        m_coll.size());

    SortHypos(mgr, m_sortedHypos->GetArray());

    // prune
    Recycler<HypothesisBase*> &recycler = mgr.GetHypoRecycler();

    size_t maxStackSize = mgr.system.options.search.stack_size;
    if (maxStackSize && m_sortedHypos->size() > maxStackSize) {
      for (size_t i = maxStackSize; i < m_sortedHypos->size(); ++i) {
        HypothesisBase *hypo = const_cast<HypothesisBase*>((*m_sortedHypos)[i]);
        recycler.Recycle(hypo);

        // delete from arclist
        if (mgr.system.options.nbest.nbest_size) {
          arcLists.Delete(hypo);
        }
      }
      m_sortedHypos->resize(maxStackSize);
    }

  }

  return *m_sortedHypos;
}

void HypothesisColl::PruneHypos(const ManagerBase &mgr, ArcLists &arcLists)
{
  size_t maxStackSize = mgr.system.options.search.stack_size;

  Recycler<HypothesisBase*> &recycler = mgr.GetHypoRecycler();

  const HypothesisBase **sortedHypos = (const HypothesisBase **) alloca(GetSize() * sizeof(const HypothesisBase *));
  SortHypos(mgr, sortedHypos);

  // update worse score
  m_worstScore = sortedHypos[maxStackSize - 1]->GetFutureScore();

  // prune
  for (size_t i = maxStackSize; i < GetSize(); ++i) {
    HypothesisBase *hypo = const_cast<HypothesisBase*>(sortedHypos[i]);

    // delete from arclist
    if (mgr.system.options.nbest.nbest_size) {
      arcLists.Delete(hypo);
    }

    // delete from collection
    Delete(hypo);

    recycler.Recycle(hypo);
  }

}

void HypothesisColl::SortHypos(const ManagerBase &mgr, const HypothesisBase **sortedHypos) const
{
  size_t maxStackSize = mgr.system.options.search.stack_size;
  //assert(maxStackSize); // can't do stack=0 - unlimited stack size. No-one ever uses that
  //assert(GetSize() > maxStackSize);
  //assert(sortedHypos.size() == GetSize());

  /*
   cerr << "UNSORTED hypos: ";
   BOOST_FOREACH(const HypothesisBase *hypo, m_coll) {
     cerr << hypo << "(" << hypo->GetFutureScore() << ")" << " ";
   }
   cerr << endl;
   */
  size_t ind = 0;
  BOOST_FOREACH(const HypothesisBase *hypo, m_coll) {
    sortedHypos[ind] = hypo;
    ++ind;
  }

  size_t indMiddle;
  if (maxStackSize == 0) {
    indMiddle = GetSize();
  } else if (GetSize() > maxStackSize) {
    indMiddle = maxStackSize;
  } else {
    // GetSize() <= maxStackSize
    indMiddle = GetSize();
  }

  const HypothesisBase **iterMiddle = sortedHypos + indMiddle;

  std::partial_sort(
    sortedHypos,
    iterMiddle,
    sortedHypos + GetSize(),
    HypothesisFutureScoreOrderer());

  /*
   cerr << "sorted hypos: ";
   for (size_t i = 0; i < sortedHypos.size(); ++i) {
     const HypothesisBase *hypo = sortedHypos[i];
     cerr << hypo << " ";
   }
   cerr << endl;
   */
}

void HypothesisColl::Delete(const HypothesisBase *hypo)
{
  //cerr << " Delete hypo=" << hypo << "(" << hypo->hash() << ")"
  //		<< " m_coll=" << m_coll.size() << endl;

  size_t erased = m_coll.erase(hypo);
  UTIL_THROW_IF2(erased != 1, "couldn't erase hypo " << hypo);
}

void HypothesisColl::Clear()
{
  m_sortedHypos = NULL;
  m_coll.clear();

  m_bestScore = -std::numeric_limits<float>::infinity();
  m_worstScore = std::numeric_limits<float>::infinity();
}

std::string HypothesisColl::Debug(const System &system) const
{
  stringstream out;
  BOOST_FOREACH (const HypothesisBase *hypo, m_coll) {
    out << hypo->Debug(system);
    out << std::endl << std::endl;
  }

  return out.str();
}

} /* namespace Moses2 */