ErrorSurface.h

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//Copyright (c) 2012, University of Cambridge
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#ifndef ERRORSURFACE_H_
#define ERRORSURFACE_H_

#include <iostream>
#include <iomanip>
#include <cmath>
#include <limits>
#include <vector>
#include <algorithm>
#include <sstream>
#include <boost/thread/mutex.hpp>

#include "MertCommon.h"
#include "BleuStats.h"
#include "IntervalData.h"

template<typename IntervalBoundary>
bool IntervalBoundarySortPredicate (const IntervalBoundary& b1,
                                    const IntervalBoundary& b2) {
  return b1.gamma < b2.gamma;
}

template<typename RD>
class ErrorSurface {
 public:
  typedef RD RefData;
  typedef typename RefData::ErrorStats ErrorStats;
  typedef IntervalData<ErrorStats> IntervalBoundary;
  typedef typename ErrorStats::Error Error;

 private:

  ErrorStats MergeInitials() const {
    ErrorStats es;
    for (typename std::vector<IntervalBoundary>::const_iterator it =
           ++ (initials.begin() ); it != initials.end(); ++it) {
      es = es + it->errorStats;
    }
    return es;
  }

  /*
   * Slightly hacky way of updating both the translation and expected translation score. First element of
   * referenced array is the translation score and the second is the expected score.
   */
  void MergeInitialScores (double scores[]) const {
    scores[0] = 0.0;
    scores[1] = 0.0;
    for (typename std::vector<IntervalBoundary>::const_iterator it =
           ++ (initials.begin() ); it != initials.end(); ++it) {
      scores[0] += it->deltaScore;
      scores[1] += it->deltaExpScore;
    }
  }

  double optimalGamma;
  Error optimalError;
  std::vector<ErrorStats> prev;
  RefData* refs;
  bool unbounded;
  std::vector<IntervalBoundary>
  initials; // Interval boundaries for left-most line segments (gamma = -infinity)
  std::vector<IntervalBoundary> prevBestIBs;
  boost::mutex mutex;

 public:

  ErrorSurface (unsigned int noOfSentences, RefData* refs) :
    refs (refs) {
    initials.resize (noOfSentences + 1);
    prevBestIBs.resize (noOfSentences + 1);
    prev.resize (noOfSentences + 1);
  }

  ErrorSurface (const ErrorSurface& other) :
    optimalGamma (other.optimalGamma), optimalError (other.optimalError), prev (
      other.prev), refs (other.refs), unbounded (other.unbounded), initials (
        other.initials), prevBestIBs (other.prevBestIBs) {
  }

  ErrorSurface& operator= (const ErrorSurface& rhs) {
    if (this == &rhs) {
      return *this;
    }
    optimalGamma = rhs.optimalGamma;
    optimalError = rhs.optimalError;
    prev = rhs.prev;
    refs = rhs.refs;
    unbounded = rhs.unbounded;
    initials = rhs.initials;
    prevBestIBs = rhs.prevBestIBs;
    return *this;
  }

  double GetOptimalGamma() {
    return optimalGamma;
  }

  Error GetOptimalError() {
    return optimalError;
  }

  bool GetUnbounded() {
    return unbounded;
  }

  void ComputeSurface() {
    std::vector<IntervalBoundary> currentIBs (initials);
    double scores[2];
    MergeInitialScores (scores);
    ErrorStats aggregateErrorStats = MergeInitials();
    sort (boundaries.begin(), boundaries.end(),
          IntervalBoundarySortPredicate<IntervalBoundary>);
    optimalGamma = boundaries.front().gamma - 1;
    optimalError = aggregateErrorStats.ComputeError();
    typename std::vector<IntervalBoundary>::iterator itNext =
      ++ (boundaries.begin() );
    unbounded = true;
    for (typename std::vector<IntervalBoundary>::iterator it =
           boundaries.begin(); it != boundaries.end(); ++it) {
      scores[0] = it->score + it->deltaScore;
      scores[1] = it->expScore + it->deltaExpScore;
      it->score = scores[0];
      it->expScore = scores[1];
      aggregateErrorStats = aggregateErrorStats + it->errorStats;
      currentIBs[it->sentence].errorStats =
        currentIBs[it->sentence].errorStats + it->errorStats;
      Error current = aggregateErrorStats.ComputeError();
      if (current > optimalError) {
        copy (++ (currentIBs.begin() ), currentIBs.end(),
              ++ (prevBestIBs.begin() ) );
        optimalError = current;
        if (itNext == boundaries.end() ) {
          optimalGamma = it->gamma + 1;
          unbounded = true;
        } else {
          optimalGamma = 0.5 * (it->gamma + itNext->gamma);
          unbounded = false;
        }
      }
      ++itNext;
    }
  }

  void Reset() {
    boundaries.clear();
    optimalGamma = 0.0;
    Error zero;
    optimalError = zero;
    copy (++ (prevBestIBs.begin() ), prevBestIBs.end(), ++ (initials.begin() ) );
  }

  void PrintErrorSurface (ostream& os) const {
    ErrorStats aggregate;
    os << optimalGamma << " " << optimalError << endl;
    for (typename std::vector<IntervalBoundary>::const_iterator it =
           initials.begin(); it != initials.end(); ++it) {
      aggregate = aggregate + it->errorStats;
      os << *it << endl;
    }
    IntervalBoundary temp;
    for (typename std::vector<IntervalBoundary>::const_iterator it =
           boundaries.begin(); it != boundaries.end(); ++it) {
      temp = *it;
      aggregate = aggregate + it->errorStats;
      temp.errorStats = aggregate;
      os << temp << endl;
    }
  }

  void WriteErrorSurface (const std::string& filename) const {
    static unsigned int lineOptCount = 0;
    std::stringstream sstream;
    sstream << filename << lineOptCount;
    std::ofstream ofs (sstream.str().c_str() );
    if (!ofs.good() ) {
      cerr << "ERROR: can't write: " << sstream.str() << '\n';
      exit (1);
    }
    tracer << "writing error surface to " << sstream.str() << '\n';
    PrintErrorSurface (ofs);
    ofs.close();
    ++lineOptCount;
  }

  void CreateInitial (Sid sid, const double gamma, const Sentence h,
                      const double modelScore, const double expScore) {
    prev[sid] = refs->ComputeErrorStats (sid, h);
    initials[sid] = IntervalBoundary (sid, gamma, prev[sid], modelScore,
                                      expScore);
  }

  void CreateInterval (Sid sid, const double gamma, const Sentence h,
                       const double modelScore, const double expScore) {
    ErrorStats next = refs->ComputeErrorStats (sid, h);
    IntervalBoundary b (sid, gamma, next - prev[sid], modelScore, expScore);
    prev[sid]  = next;
    mutex.lock();
    boundaries.push_back (b);
    mutex.unlock();
  }

  std::vector<IntervalBoundary>
  boundaries; // Interval boundaries where top-most line segment changes

};

#endif /* ERRORSURFACE_H_ */