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#include "DistortionScoreProducer.h"
#include "FFState.h"
#include "moses/Range.h"
#include "moses/StaticData.h"
#include "moses/Hypothesis.h"
using namespace std;
namespace Moses
{
struct DistortionState_traditional : public FFState {
Range range;
int first_gap;
DistortionState_traditional(const Range& wr, int fg) : range(wr), first_gap(fg) {}
size_t hash() const {
return range.GetEndPos();
}
virtual bool operator==(const FFState& other) const {
const DistortionState_traditional& o =
static_cast<const DistortionState_traditional&>(other);
return range.GetEndPos() == o.range.GetEndPos();
}
};
std::vector<const DistortionScoreProducer*> DistortionScoreProducer::s_staticColl;
DistortionScoreProducer::DistortionScoreProducer(const std::string &line)
: StatefulFeatureFunction(1, line)
{
s_staticColl.push_back(this);
ReadParameters();
}
const FFState* DistortionScoreProducer::EmptyHypothesisState(const InputType &input) const
{
// fake previous translated phrase start and end
size_t start = NOT_FOUND;
size_t end = NOT_FOUND;
if (input.m_frontSpanCoveredLength > 0) {
// can happen with --continue-partial-translation
start = 0;
end = input.m_frontSpanCoveredLength -1;
}
return new DistortionState_traditional(
Range(start, end),
NOT_FOUND);
}
float DistortionScoreProducer::CalculateDistortionScore(const Hypothesis& hypo,
const Range &prev, const Range &curr, const int FirstGap)
{
if(!StaticData::Instance().UseEarlyDistortionCost()) {
return - (float) hypo.GetInput().ComputeDistortionDistance(prev, curr);
} else {
/* Pay distortion score as soon as possible, from Moore and Quirk MT Summit 2007
Definitions:
S : current source range
S' : last translated source phrase range
S'' : longest fully-translated initial segment
*/
int prefixEndPos = (int)FirstGap-1;
if((int)FirstGap==-1)
prefixEndPos = -1;
// case1: S is adjacent to S'' => return 0
if ((int) curr.GetStartPos() == prefixEndPos+1) {
IFVERBOSE(4) std::cerr<< "MQ07disto:case1" << std::endl;
return 0;
}
// case2: S is to the left of S' => return 2(length(S))
if ((int) curr.GetEndPos() < (int) prev.GetEndPos()) {
IFVERBOSE(4) std::cerr<< "MQ07disto:case2" << std::endl;
return (float) -2*(int)curr.GetNumWordsCovered();
}
// case3: S' is a subsequence of S'' => return 2(nbWordBetween(S,S'')+length(S))
if ((int) prev.GetEndPos() <= prefixEndPos) {
IFVERBOSE(4) std::cerr<< "MQ07disto:case3" << std::endl;
int z = (int)curr.GetStartPos()-prefixEndPos - 1;
return (float) -2*(z + (int)curr.GetNumWordsCovered());
}
// case4: otherwise => return 2(nbWordBetween(S,S')+length(S))
IFVERBOSE(4) std::cerr<< "MQ07disto:case4" << std::endl;
return (float) -2*((int)curr.GetNumWordsBetween(prev) + (int)curr.GetNumWordsCovered());
}
}
FFState* DistortionScoreProducer::EvaluateWhenApplied(
const Hypothesis& hypo,
const FFState* prev_state,
ScoreComponentCollection* out) const
{
const DistortionState_traditional* prev = static_cast<const DistortionState_traditional*>(prev_state);
const float distortionScore = CalculateDistortionScore(
hypo,
prev->range,
hypo.GetCurrSourceWordsRange(),
prev->first_gap);
out->PlusEquals(this, distortionScore);
DistortionState_traditional* res = new DistortionState_traditional(
hypo.GetCurrSourceWordsRange(),
hypo.GetWordsBitmap().GetFirstGapPos());
return res;
}
}
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