mirror of
https://github.com/moses-smt/mosesdecoder.git
synced 2024-12-27 05:55:02 +03:00
407 lines
15 KiB
C++
407 lines
15 KiB
C++
#include "Manager.h"
|
|
#include "Timer.h"
|
|
#include "SearchNormal.h"
|
|
|
|
using namespace std;
|
|
|
|
namespace Moses
|
|
{
|
|
/**
|
|
* Organizing main function
|
|
*
|
|
* /param source input sentence
|
|
* /param transOptColl collection of translation options to be used for this sentence
|
|
*/
|
|
SearchNormal::SearchNormal(Manager& manager, const InputType &source, const TranslationOptionCollection &transOptColl)
|
|
:Search(manager)
|
|
,m_source(source)
|
|
,m_hypoStackColl(source.GetSize() + 1)
|
|
,m_initialTargetPhrase(source.m_initialTargetPhrase)
|
|
,m_start(clock())
|
|
,interrupted_flag(0)
|
|
,m_transOptColl(transOptColl)
|
|
{
|
|
VERBOSE(1, "Translating: " << m_source << endl);
|
|
const StaticData &staticData = StaticData::Instance();
|
|
|
|
if (m_initialTargetPhrase.GetSize() > 0) {
|
|
VERBOSE(1, "Search extends partial output: " << m_initialTargetPhrase<<endl);
|
|
}
|
|
|
|
// only if constraint decoding (having to match a specified output)
|
|
long sentenceID = source.GetTranslationId();
|
|
m_constraint = staticData.GetConstrainingPhrase(sentenceID);
|
|
if (m_constraint) {
|
|
VERBOSE(1, "Search constraint to output: " << *m_constraint<<endl);
|
|
}
|
|
|
|
// initialize the stacks: create data structure and set limits
|
|
std::vector < HypothesisStackNormal >::iterator iterStack;
|
|
for (size_t ind = 0 ; ind < m_hypoStackColl.size() ; ++ind) {
|
|
HypothesisStackNormal *sourceHypoColl = new HypothesisStackNormal(m_manager);
|
|
sourceHypoColl->SetMaxHypoStackSize(staticData.GetMaxHypoStackSize(),staticData.GetMinHypoStackDiversity());
|
|
sourceHypoColl->SetBeamWidth(staticData.GetBeamWidth());
|
|
|
|
m_hypoStackColl[ind] = sourceHypoColl;
|
|
}
|
|
}
|
|
|
|
SearchNormal::~SearchNormal()
|
|
{
|
|
RemoveAllInColl(m_hypoStackColl);
|
|
}
|
|
|
|
/**
|
|
* Main decoder loop that translates a sentence by expanding
|
|
* hypotheses stack by stack, until the end of the sentence.
|
|
*/
|
|
void SearchNormal::ProcessSentence()
|
|
{
|
|
const StaticData &staticData = StaticData::Instance();
|
|
SentenceStats &stats = m_manager.GetSentenceStats();
|
|
clock_t t=0; // used to track time for steps
|
|
|
|
// initial seed hypothesis: nothing translated, no words produced
|
|
Hypothesis *hypo = Hypothesis::Create(m_manager,m_source, m_initialTargetPhrase);
|
|
m_hypoStackColl[0]->AddPrune(hypo);
|
|
|
|
// go through each stack
|
|
std::vector < HypothesisStack* >::iterator iterStack;
|
|
for (iterStack = m_hypoStackColl.begin() ; iterStack != m_hypoStackColl.end() ; ++iterStack) {
|
|
// check if decoding ran out of time
|
|
double _elapsed_time = GetUserTime();
|
|
if (_elapsed_time > staticData.GetTimeoutThreshold()) {
|
|
VERBOSE(1,"Decoding is out of time (" << _elapsed_time << "," << staticData.GetTimeoutThreshold() << ")" << std::endl);
|
|
interrupted_flag = 1;
|
|
return;
|
|
}
|
|
HypothesisStackNormal &sourceHypoColl = *static_cast<HypothesisStackNormal*>(*iterStack);
|
|
|
|
// the stack is pruned before processing (lazy pruning):
|
|
VERBOSE(3,"processing hypothesis from next stack");
|
|
IFVERBOSE(2) {
|
|
t = clock();
|
|
}
|
|
sourceHypoColl.PruneToSize(staticData.GetMaxHypoStackSize());
|
|
VERBOSE(3,std::endl);
|
|
sourceHypoColl.CleanupArcList();
|
|
IFVERBOSE(2) {
|
|
stats.AddTimeStack( clock()-t );
|
|
}
|
|
|
|
// go through each hypothesis on the stack and try to expand it
|
|
HypothesisStackNormal::const_iterator iterHypo;
|
|
for (iterHypo = sourceHypoColl.begin() ; iterHypo != sourceHypoColl.end() ; ++iterHypo) {
|
|
Hypothesis &hypothesis = **iterHypo;
|
|
ProcessOneHypothesis(hypothesis); // expand the hypothesis
|
|
}
|
|
// some logging
|
|
IFVERBOSE(2) {
|
|
OutputHypoStackSize();
|
|
}
|
|
|
|
// this stack is fully expanded;
|
|
actual_hypoStack = &sourceHypoColl;
|
|
}
|
|
|
|
// some more logging
|
|
IFVERBOSE(2) {
|
|
m_manager.GetSentenceStats().SetTimeTotal( clock()-m_start );
|
|
}
|
|
VERBOSE(2, m_manager.GetSentenceStats());
|
|
}
|
|
|
|
|
|
/** Find all translation options to expand one hypothesis, trigger expansion
|
|
* this is mostly a check for overlap with already covered words, and for
|
|
* violation of reordering limits.
|
|
* \param hypothesis hypothesis to be expanded upon
|
|
*/
|
|
void SearchNormal::ProcessOneHypothesis(const Hypothesis &hypothesis)
|
|
{
|
|
// since we check for reordering limits, its good to have that limit handy
|
|
int maxDistortion = StaticData::Instance().GetMaxDistortion();
|
|
bool isWordLattice = StaticData::Instance().GetInputType() == WordLatticeInput;
|
|
|
|
// no limit of reordering: only check for overlap
|
|
if (maxDistortion < 0) {
|
|
const WordsBitmap hypoBitmap = hypothesis.GetWordsBitmap();
|
|
const size_t hypoFirstGapPos = hypoBitmap.GetFirstGapPos()
|
|
, sourceSize = m_source.GetSize();
|
|
|
|
for (size_t startPos = hypoFirstGapPos ; startPos < sourceSize ; ++startPos) {
|
|
size_t maxSize = sourceSize - startPos;
|
|
size_t maxSizePhrase = StaticData::Instance().GetMaxPhraseLength();
|
|
maxSize = (maxSize < maxSizePhrase) ? maxSize : maxSizePhrase;
|
|
|
|
for (size_t endPos = startPos ; endPos < startPos + maxSize ; ++endPos) {
|
|
// basic checks
|
|
// there have to be translation options
|
|
if (m_transOptColl.GetTranslationOptionList(WordsRange(startPos, endPos)).size() == 0 ||
|
|
// no overlap with existing words
|
|
hypoBitmap.Overlap(WordsRange(startPos, endPos)) ||
|
|
// specified reordering constraints (set with -monotone-at-punctuation or xml)
|
|
!m_source.GetReorderingConstraint().Check( hypoBitmap, startPos, endPos ) ) {
|
|
continue;
|
|
}
|
|
|
|
//TODO: does this method include incompatible WordLattice hypotheses?
|
|
ExpandAllHypotheses(hypothesis, startPos, endPos);
|
|
}
|
|
}
|
|
|
|
return; // done with special case (no reordering limit)
|
|
}
|
|
|
|
// if there are reordering limits, make sure it is not violated
|
|
// the coverage bitmap is handy here (and the position of the first gap)
|
|
const WordsBitmap hypoBitmap = hypothesis.GetWordsBitmap();
|
|
const size_t hypoFirstGapPos = hypoBitmap.GetFirstGapPos()
|
|
, sourceSize = m_source.GetSize();
|
|
|
|
// MAIN LOOP. go through each possible range
|
|
for (size_t startPos = hypoFirstGapPos ; startPos < sourceSize ; ++startPos) {
|
|
// don't bother expanding phrases if the first position is already taken
|
|
if(hypoBitmap.GetValue(startPos))
|
|
continue;
|
|
|
|
WordsRange prevRange = hypothesis.GetCurrSourceWordsRange();
|
|
|
|
size_t maxSize = sourceSize - startPos;
|
|
size_t maxSizePhrase = StaticData::Instance().GetMaxPhraseLength();
|
|
maxSize = (maxSize < maxSizePhrase) ? maxSize : maxSizePhrase;
|
|
size_t closestLeft = hypoBitmap.GetEdgeToTheLeftOf(startPos);
|
|
if (isWordLattice) {
|
|
// first question: is there a path from the closest translated word to the left
|
|
// of the hypothesized extension to the start of the hypothesized extension?
|
|
// long version: is there anything to our left? is it farther left than where we're starting anyway? can we get to it?
|
|
// closestLeft is exclusive: a value of 3 means 2 is covered, our arc is currently ENDING at 3 and can start at 3 implicitly
|
|
if (closestLeft != 0 && closestLeft != startPos && !m_source.CanIGetFromAToB(closestLeft, startPos)) {
|
|
continue;
|
|
}
|
|
if (prevRange.GetStartPos() != NOT_FOUND &&
|
|
prevRange.GetStartPos() > startPos && !m_source.CanIGetFromAToB(startPos, prevRange.GetStartPos())) {
|
|
continue;
|
|
}
|
|
}
|
|
|
|
WordsRange currentStartRange(startPos, startPos);
|
|
if(m_source.ComputeDistortionDistance(prevRange, currentStartRange) > maxDistortion)
|
|
continue;
|
|
|
|
for (size_t endPos = startPos ; endPos < startPos + maxSize ; ++endPos) {
|
|
// basic checks
|
|
WordsRange extRange(startPos, endPos);
|
|
// there have to be translation options
|
|
if (m_transOptColl.GetTranslationOptionList(extRange).size() == 0 ||
|
|
// no overlap with existing words
|
|
hypoBitmap.Overlap(extRange) ||
|
|
// specified reordering constraints (set with -monotone-at-punctuation or xml)
|
|
!m_source.GetReorderingConstraint().Check( hypoBitmap, startPos, endPos ) || //
|
|
// connection in input word lattice
|
|
(isWordLattice && !m_source.IsCoveragePossible(extRange))) {
|
|
continue;
|
|
}
|
|
|
|
// ask second question here:
|
|
// we already know we can get to our starting point from the closest thing to the left. We now ask the follow up:
|
|
// can we get from our end to the closest thing on the right?
|
|
// long version: is anything to our right? is it farther right than our (inclusive) end? can our end reach it?
|
|
bool leftMostEdge = (hypoFirstGapPos == startPos);
|
|
|
|
// closest right definition:
|
|
size_t closestRight = hypoBitmap.GetEdgeToTheRightOf(endPos);
|
|
if (isWordLattice) {
|
|
//if (!leftMostEdge && closestRight != endPos && closestRight != sourceSize && !m_source.CanIGetFromAToB(endPos, closestRight + 1)) {
|
|
if (closestRight != endPos && ((closestRight + 1) < sourceSize) && !m_source.CanIGetFromAToB(endPos + 1, closestRight + 1)) {
|
|
continue;
|
|
}
|
|
}
|
|
|
|
// any length extension is okay if starting at left-most edge
|
|
if (leftMostEdge) {
|
|
ExpandAllHypotheses(hypothesis, startPos, endPos);
|
|
}
|
|
// starting somewhere other than left-most edge, use caution
|
|
else {
|
|
// the basic idea is this: we would like to translate a phrase starting
|
|
// from a position further right than the left-most open gap. The
|
|
// distortion penalty for the following phrase will be computed relative
|
|
// to the ending position of the current extension, so we ask now what
|
|
// its maximum value will be (which will always be the value of the
|
|
// hypothesis starting at the left-most edge). If this value is less than
|
|
// the distortion limit, we don't allow this extension to be made.
|
|
WordsRange bestNextExtension(hypoFirstGapPos, hypoFirstGapPos);
|
|
int required_distortion =
|
|
m_source.ComputeDistortionDistance(extRange, bestNextExtension);
|
|
|
|
if (required_distortion > maxDistortion) {
|
|
continue;
|
|
}
|
|
|
|
// everything is fine, we're good to go
|
|
ExpandAllHypotheses(hypothesis, startPos, endPos);
|
|
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
/**
|
|
* Expand a hypothesis given a list of translation options
|
|
* \param hypothesis hypothesis to be expanded upon
|
|
* \param startPos first word position of span covered
|
|
* \param endPos last word position of span covered
|
|
*/
|
|
|
|
void SearchNormal::ExpandAllHypotheses(const Hypothesis &hypothesis, size_t startPos, size_t endPos)
|
|
{
|
|
// early discarding: check if hypothesis is too bad to build
|
|
// this idea is explained in (Moore&Quirk, MT Summit 2007)
|
|
float expectedScore = 0.0f;
|
|
if (StaticData::Instance().UseEarlyDiscarding()) {
|
|
// expected score is based on score of current hypothesis
|
|
expectedScore = hypothesis.GetScore();
|
|
|
|
// add new future score estimate
|
|
expectedScore += m_transOptColl.GetFutureScore().CalcFutureScore( hypothesis.GetWordsBitmap(), startPos, endPos );
|
|
}
|
|
|
|
// loop through all translation options
|
|
const TranslationOptionList &transOptList = m_transOptColl.GetTranslationOptionList(WordsRange(startPos, endPos));
|
|
TranslationOptionList::const_iterator iter;
|
|
for (iter = transOptList.begin() ; iter != transOptList.end() ; ++iter) {
|
|
ExpandHypothesis(hypothesis, **iter, expectedScore);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Expand one hypothesis with a translation option.
|
|
* this involves initial creation, scoring and adding it to the proper stack
|
|
* \param hypothesis hypothesis to be expanded upon
|
|
* \param transOpt translation option (phrase translation)
|
|
* that is applied to create the new hypothesis
|
|
* \param expectedScore base score for early discarding
|
|
* (base hypothesis score plus future score estimation)
|
|
*/
|
|
void SearchNormal::ExpandHypothesis(const Hypothesis &hypothesis, const TranslationOption &transOpt, float expectedScore)
|
|
{
|
|
const StaticData &staticData = StaticData::Instance();
|
|
SentenceStats &stats = m_manager.GetSentenceStats();
|
|
clock_t t=0; // used to track time for steps
|
|
|
|
Hypothesis *newHypo;
|
|
if (! staticData.UseEarlyDiscarding()) {
|
|
// simple build, no questions asked
|
|
IFVERBOSE(2) {
|
|
t = clock();
|
|
}
|
|
newHypo = hypothesis.CreateNext(transOpt, m_constraint);
|
|
IFVERBOSE(2) {
|
|
stats.AddTimeBuildHyp( clock()-t );
|
|
}
|
|
if (newHypo==NULL) return;
|
|
newHypo->CalcScore(m_transOptColl.GetFutureScore());
|
|
} else
|
|
// early discarding: check if hypothesis is too bad to build
|
|
{
|
|
// worst possible score may have changed -> recompute
|
|
size_t wordsTranslated = hypothesis.GetWordsBitmap().GetNumWordsCovered() + transOpt.GetSize();
|
|
float allowedScore = m_hypoStackColl[wordsTranslated]->GetWorstScore();
|
|
if (staticData.GetMinHypoStackDiversity()) {
|
|
WordsBitmapID id = hypothesis.GetWordsBitmap().GetIDPlus(transOpt.GetStartPos(), transOpt.GetEndPos());
|
|
float allowedScoreForBitmap = m_hypoStackColl[wordsTranslated]->GetWorstScoreForBitmap( id );
|
|
allowedScore = std::min( allowedScore, allowedScoreForBitmap );
|
|
}
|
|
allowedScore += staticData.GetEarlyDiscardingThreshold();
|
|
|
|
// add expected score of translation option
|
|
expectedScore += transOpt.GetFutureScore();
|
|
// TRACE_ERR("EXPECTED diff: " << (newHypo->GetTotalScore()-expectedScore) << " (pre " << (newHypo->GetTotalScore()-expectedScorePre) << ") " << hypothesis.GetTargetPhrase() << " ... " << transOpt.GetTargetPhrase() << " [" << expectedScorePre << "," << expectedScore << "," << newHypo->GetTotalScore() << "]" << endl);
|
|
|
|
// check if transOpt score push it already below limit
|
|
if (expectedScore < allowedScore) {
|
|
IFVERBOSE(2) {
|
|
stats.AddNotBuilt();
|
|
}
|
|
return;
|
|
}
|
|
|
|
// build the hypothesis without scoring
|
|
IFVERBOSE(2) {
|
|
t = clock();
|
|
}
|
|
newHypo = hypothesis.CreateNext(transOpt, m_constraint);
|
|
if (newHypo==NULL) return;
|
|
IFVERBOSE(2) {
|
|
stats.AddTimeBuildHyp( clock()-t );
|
|
}
|
|
|
|
// compute expected score (all but correct LM)
|
|
expectedScore = newHypo->CalcExpectedScore( m_transOptColl.GetFutureScore() );
|
|
// ... and check if that is below the limit
|
|
if (expectedScore < allowedScore) {
|
|
IFVERBOSE(2) {
|
|
stats.AddEarlyDiscarded();
|
|
}
|
|
FREEHYPO( newHypo );
|
|
return;
|
|
}
|
|
|
|
// ok, all is good, compute remaining scores
|
|
newHypo->CalcRemainingScore();
|
|
|
|
}
|
|
|
|
// logging for the curious
|
|
IFVERBOSE(3) {
|
|
newHypo->PrintHypothesis();
|
|
}
|
|
|
|
// add to hypothesis stack
|
|
size_t wordsTranslated = newHypo->GetWordsBitmap().GetNumWordsCovered();
|
|
IFVERBOSE(2) {
|
|
t = clock();
|
|
}
|
|
m_hypoStackColl[wordsTranslated]->AddPrune(newHypo);
|
|
IFVERBOSE(2) {
|
|
stats.AddTimeStack( clock()-t );
|
|
}
|
|
}
|
|
|
|
const std::vector < HypothesisStack* >& SearchNormal::GetHypothesisStacks() const
|
|
{
|
|
return m_hypoStackColl;
|
|
}
|
|
|
|
/**
|
|
* Find best hypothesis on the last stack.
|
|
* This is the end point of the best translation, which can be traced back from here
|
|
*/
|
|
const Hypothesis *SearchNormal::GetBestHypothesis() const
|
|
{
|
|
if (interrupted_flag == 0) {
|
|
const HypothesisStackNormal &hypoColl = *static_cast<HypothesisStackNormal*>(m_hypoStackColl.back());
|
|
return hypoColl.GetBestHypothesis();
|
|
} else {
|
|
const HypothesisStackNormal &hypoColl = *actual_hypoStack;
|
|
return hypoColl.GetBestHypothesis();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Logging of hypothesis stack sizes
|
|
*/
|
|
void SearchNormal::OutputHypoStackSize()
|
|
{
|
|
std::vector < HypothesisStack* >::const_iterator iterStack = m_hypoStackColl.begin();
|
|
TRACE_ERR( "Stack sizes: " << (int)(*iterStack)->size());
|
|
for (++iterStack; iterStack != m_hypoStackColl.end() ; ++iterStack) {
|
|
TRACE_ERR( ", " << (int)(*iterStack)->size());
|
|
}
|
|
TRACE_ERR( endl);
|
|
}
|
|
|
|
}
|