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/*
* Search.cpp
*
* Created on: 16 Nov 2015
* Author: hieu
*/
#include "Search.h"
#include "Manager.h"
#include "../System.h"
#include "../legacy/Bitmap.h"
#include "../legacy/Range.h"
namespace Moses2
{
Search::Search(Manager &mgr) :
mgr(mgr)
{
// TODO Auto-generated constructor stub
}
Search::~Search()
{
// TODO Auto-generated destructor stub
}
bool Search::CanExtend(const Bitmap &hypoBitmap, size_t hypoRangeEndPos,
const Range &pathRange)
{
const size_t hypoFirstGapPos = hypoBitmap.GetFirstGapPos();
//cerr << "DOING " << hypoBitmap << " [" << hypoRange.GetStartPos() << " " << hypoRange.GetEndPos() << "]"
// " [" << pathRange.GetStartPos() << " " << pathRange.GetEndPos() << "]";
if (hypoBitmap.Overlap(pathRange)) {
//cerr << " NO" << endl;
return false;
}
if (mgr.system.options.reordering.max_distortion >= 0) {
// distortion limit
int distortion = ComputeDistortionDistance(hypoRangeEndPos,
pathRange.GetStartPos());
if (distortion > mgr.system.options.reordering.max_distortion) {
//cerr << " NO" << endl;
return false;
}
}
// 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
// TODO is this relevant? only for lattice input?
// 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 isLeftMostEdge = (hypoFirstGapPos == pathRange.GetStartPos());
size_t closestRight = hypoBitmap.GetEdgeToTheRightOf(pathRange.GetEndPos());
/*
if (isWordLattice) {
if (closestRight != endPos
&& ((closestRight + 1) < sourceSize)
&& !m_source.CanIGetFromAToB(endPos + 1, closestRight + 1)) {
continue;
}
}
*/
if (isLeftMostEdge) {
// any length extension is okay if starting at left-most edge
}
else { // starting somewhere other than left-most edge, use caution
// 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.
Range bestNextExtension(hypoFirstGapPos, hypoFirstGapPos);
if (ComputeDistortionDistance(pathRange.GetEndPos(),
bestNextExtension.GetStartPos()) > mgr.system.options.reordering.max_distortion) {
//cerr << " NO" << endl;
return false;
}
// everything is fine, we're good to go
}
return true;
}
}
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