RefsData.cpp

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//Copyright (c) 2012, University of Cambridge
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#include "RefsData.h"

RefsData::RefsData() {};

RefsData RefsData::dummy;

RefsData::RefsData (const std::vector<Sentence>& refs) {
  for (unsigned int n = 0; n < BleuStats::MAX_BLEU_ORDER; ++n) {
    std::vector<NGramToCountMap> tmpCounts (refs.size() );
    for (unsigned int k = 0; k < refs.size(); ++k) {
      int refssize_minus_n = refs[k].size() -
                             n; // needs to be an int, not a unsigned int in case it is negative
      for (int i = 0; i < refssize_minus_n; ++i) {
        NGram u = SubStr (refs[k], i, n);
        refCounts[u] = 1;
        tmpCounts[k][u]++;
      }
    }
    for (unsigned int k = 0; k < refs.size(); ++k) {
      for (NGramToCountMap::iterator it = refCounts.begin();
           it != refCounts.end(); ++it) {
        it->second = max (it->second, tmpCounts[k][it->first]);
      }
    }
  }
  for (unsigned int k = 0; k < refs.size(); ++k) {
    refLengths.push_back (refs[k].size() );
  }
  sort (refLengths.begin(), refLengths.end() );
}

BleuStats RefsData::ComputeBleuStats (const Sentence& hyp) const {
  BleuStats bs;
  bs.refLength = ClosestReferenceLength (hyp.size() );
  for (unsigned int n = 0; n < BleuStats::MAX_BLEU_ORDER && n < hyp.size();
       ++n) {
    NGramToCountMap hypCounts;
    if (hyp.size() > n) {
      bs.tots[n] = hyp.size() - n;
    }
    for (unsigned int i = 0; i < hyp.size() - n; ++i) {
      hypCounts[SubStr (hyp, i, n)]++;
    }
    for (NGramToCountMap::const_iterator hit = hypCounts.begin();
         hit != hypCounts.end(); ++hit) {
      NGramToCountMap::const_iterator rit = refCounts.find (hit->first);
      bs.hits[n] += min (rit == refCounts.end() ? 0 : rit->second,
                         hit->second); // Sum clipped counts
    }
  }
  return bs;
}

NGram RefsData::SubStr (const Sentence& s, const unsigned int n,
                        const unsigned int l) const {
  return NGram (s.begin() + n, s.begin() + n + l + 1);
}

unsigned int RefsData::ClosestReferenceLength (
  const unsigned int hypLength) const {
  unsigned int refLength = 0;
  unsigned int refDistance = numeric_limits<unsigned int>::max();
  for (unsigned int k = 0; k < refLengths.size(); ++k) {
    unsigned int distance = abs ( (int) refLengths[k] - (int) hypLength);
    if (distance < refDistance) {
      refDistance = distance;
      refLength = refLengths[k];
    }
  }
  return refLength;
}

std::string RefsData::ToString (const char separator = ' ') const {
  ostringstream oss;
  for (NGramToCountMap::const_iterator it = refCounts.begin();
       it != refCounts.end(); ++it) {
    NGram u = it->first;
    unsigned int count = it->second;
    for (int w = 0; w < u.size(); ++w) {
      if (w > 0) {
        oss << " ";
      }
      oss << u[w];
    }
    oss << '\t' << count << separator;
  }
  return oss.str();
}

std::vector<std::vector<std::string> > LoadRefFiles (std::vector<std::string>
    files) {
  tracer << "loading and initializing reference ngrams...\n";
  std::vector<std::vector<std::string> > refsStr (files.size() );
  for (unsigned int r = 0; r < files.size(); ++r) {
    std::ifstream ifs (files[r].c_str() );
    if (!ifs.good() ) {
      cerr << "ERROR: unable to open file " << files[r] << '\n';
      exit (1);
    }
    std::string line;
    refsStr[r].push_back ("");
    while (getline (ifs, line) ) {
      refsStr[r].push_back (line);
    }
    if (opts.verbose) {
      tracer << "loaded " << refsStr[r].size() - 1 << " translations from "
             << files[r] << '\n';
    }
    ifs.close();
  }
  return refsStr;
}

void IntegerEncRefs::LoadRefData (std::vector<std::string> files) {
  std::vector<std::vector<std::string> > refsStr = LoadRefFiles (files);
  refsData.push_back (RefsData::dummy);
  for (unsigned int sid = 0; sid < refsStr[0].size() - 1 ; ++sid) {
    std::vector<Sentence> refsIdx;
    for (unsigned int r = 0; r < files.size(); ++r) {
      std::istringstream iss (refsStr[r][sid + 1]);
      Sentence s;
      Wid w;
      while (iss >> w) {
        s.push_back (w);
      }
      refsIdx.push_back (s);
    }
    refsData.push_back (RefsData (refsIdx) );
  }
}

IntegerEncRefs::ErrorStats IntegerEncRefs::ComputeErrorStats (Sid sid,
    Sentence h) const {
  if (sid + 1 > refsData.size() ) {
    cerr << "ERROR: no references loaded for sentence s=" << sid << '\n';
    exit (1);
  }
  return refsData[sid].ComputeBleuStats (h);
}