mosesdecoder/moses/ReorderingConstraint.cpp
2013-11-19 17:23:19 +00:00

238 lines
7.6 KiB
C++

// $Id$
// vim:tabstop=2
/***********************************************************************
Moses - factored phrase-based language decoder
Copyright (C) 2008 University of Edinburgh
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
***********************************************************************/
#include "ReorderingConstraint.h"
#include "InputType.h"
#include "StaticData.h"
#include "WordsBitmap.h"
namespace Moses
{
//! allocate memory for reordering walls
void ReorderingConstraint::InitializeWalls(size_t size)
{
m_size = size;
m_wall = (bool*) malloc(sizeof(bool) * size);
m_localWall = (size_t*) malloc(sizeof(size_t) * size);
for (size_t pos = 0 ; pos < m_size ; pos++) {
m_wall[pos] = false;
m_localWall[pos] = NOT_A_ZONE;
}
}
//! set value at a particular position
void ReorderingConstraint::SetWall( size_t pos, bool value )
{
VERBOSE(3,"SETTING reordering wall at position " << pos << std::endl);
m_wall[pos] = value;
m_active = true;
}
//! has to be called to localized walls
void ReorderingConstraint::FinalizeWalls()
{
for(size_t z = 0; z < m_zone.size(); z++ ) {
const size_t startZone = m_zone[z][0];
const size_t endZone = m_zone[z][1];// note: wall after endZone is not local
for( size_t pos = startZone; pos < endZone; pos++ ) {
if (m_wall[ pos ]) {
m_localWall[ pos ] = z;
m_wall[ pos ] = false;
VERBOSE(3,"SETTING local wall " << pos << std::endl);
}
// enforce that local walls only apply to innermost zone
else if (m_localWall[ pos ] != NOT_A_ZONE) {
size_t assigned_z = m_localWall[ pos ];
if ((m_zone[assigned_z][0] < startZone) ||
(m_zone[assigned_z][1] > endZone)) {
m_localWall[ pos ] = z;
}
}
}
}
}
//! set walls based on "-monotone-at-punctuation" flag
void ReorderingConstraint::SetMonotoneAtPunctuation( const Phrase &sentence )
{
for( size_t i=0; i<sentence.GetSize(); i++ ) {
const Word& word = sentence.GetWord(i);
if (word[0]->GetString() == "," ||
word[0]->GetString() == "." ||
word[0]->GetString() == "!" ||
word[0]->GetString() == "?" ||
word[0]->GetString() == ":" ||
word[0]->GetString() == ";" ||
word[0]->GetString() == "\"") {
// set wall before and after punc, but not at sentence start, end
if (i>0 && i<m_size-1) SetWall( i, true );
if (i>1) SetWall( i-1, true );
}
}
}
//! set a reordering zone (once entered, need to finish)
void ReorderingConstraint::SetZone( size_t startPos, size_t endPos )
{
VERBOSE(3,"SETTING zone " << startPos << "-" << endPos << std::endl);
std::vector< size_t > newZone;
newZone.push_back( startPos );
newZone.push_back( endPos );
m_zone.push_back( newZone );
m_active = true;
}
//! check if the current hypothesis extension violates reordering constraints
bool ReorderingConstraint::Check( const WordsBitmap &bitmap, size_t startPos, size_t endPos ) const
{
// nothing to be checked, we are done
if (! IsActive() ) return true;
VERBOSE(3,"Check " << bitmap << " " << startPos << "-" << endPos);
// check walls
size_t firstGapPos = bitmap.GetFirstGapPos();
// filling first gap -> no wall violation possible
if (firstGapPos != startPos) {
// if there is a wall before the last word,
// we created a gap while moving through wall
// -> violation
for( size_t pos = firstGapPos; pos < endPos; pos++ ) {
if( GetWall( pos ) ) {
VERBOSE(3," hitting wall " << pos << std::endl);
return false;
}
}
}
// monotone -> no violation possible
size_t lastPos = bitmap.GetLastPos();
if ((lastPos == NOT_FOUND && startPos == 0) || // nothing translated
(firstGapPos > lastPos && // no gaps
firstGapPos == startPos)) { // translating first empty word
VERBOSE(3," montone, fine." << std::endl);
return true;
}
// check zones
for(size_t z = 0; z < m_zone.size(); z++ ) {
const size_t startZone = m_zone[z][0];
const size_t endZone = m_zone[z][1];
// fine, if translation has not reached zone yet and phrase outside zone
if (lastPos < startZone && ( endPos < startZone || startPos > endZone ) ) {
continue;
}
// already completely translated zone, no violations possible
if (firstGapPos > endZone) {
continue;
}
// some words are translated beyond the start
// let's look closer if some are in the zone
size_t numWordsInZoneTranslated = 0;
if (lastPos >= startZone) {
for(size_t pos = startZone; pos <= endZone; pos++ ) {
if( bitmap.GetValue( pos ) ) {
numWordsInZoneTranslated++;
}
}
}
// all words in zone translated, no violation possible
if (numWordsInZoneTranslated == endZone-startZone+1) {
continue;
}
// flag if this is an active zone
bool activeZone = (numWordsInZoneTranslated > 0);
// fine, if zone completely untranslated and phrase outside zone
if (!activeZone && ( endPos < startZone || startPos > endZone ) ) {
continue;
}
// violation, if phrase completely outside active zone
if (activeZone && ( endPos < startZone || startPos > endZone ) ) {
VERBOSE(3," outside active zone" << std::endl);
return false;
}
// ok, this is what we know now:
// * the phrase is in the zone (at least partially)
// * either zone is already active, or it becomes active now
// check, if we are setting us up for a dead end due to distortion limits
size_t distortionLimit = (size_t)StaticData::Instance().GetMaxDistortion();
if (startPos != firstGapPos && endZone-firstGapPos >= distortionLimit) {
VERBOSE(3," dead end due to distortion limit" << std::endl);
return false;
}
// let us check on phrases that are partially outside
// phrase overlaps at the beginning, always ok
if (startPos <= startZone) {
continue;
}
// phrase goes beyond end, has to fill zone completely
if (endPos > endZone) {
if (endZone-startPos+1 < // num. words filled in by phrase
endZone-startZone+1-numWordsInZoneTranslated) { // num. untranslated
VERBOSE(3," overlap end, but not completing" << std::endl);
return false;
} else {
continue;
}
}
// now we are down to phrases that are completely inside the zone
// we have to check local walls
bool seenUntranslatedBeforeStartPos = false;
for(size_t pos = startZone; pos < endZone && pos < endPos; pos++ ) {
// be careful when there is a gap before phrase
if( !bitmap.GetValue( pos ) // untranslated word
&& pos < startPos ) { // before startPos
seenUntranslatedBeforeStartPos = true;
}
if( seenUntranslatedBeforeStartPos && GetLocalWall( pos, z ) ) {
VERBOSE(3," local wall violation" << std::endl);
return false;
}
}
// passed all checks for this zone, on to the next one
}
// passed all checks, no violations
VERBOSE(3," fine." << std::endl);
return true;
}
}