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/***********************************************************************
Moses - statistical machine translation system
Copyright (C) 2006-2011 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 "ScfgRule.h"
#include "Node.h"
#include "Subgraph.h"
#include <algorithm>
namespace Moses {
namespace GHKM {
ScfgRule::ScfgRule(const Subgraph &fragment)
: m_sourceLHS("X", NonTerminal)
, m_targetLHS(fragment.GetRoot()->GetLabel(), NonTerminal)
, m_pcfgScore(fragment.GetPcfgScore())
{
// Source RHS
const std::set<const Node *> &leaves = fragment.GetLeaves();
std::vector<const Node *> sourceRHSNodes;
sourceRHSNodes.reserve(leaves.size());
for (std::set<const Node *>::const_iterator p(leaves.begin());
p != leaves.end(); ++p) {
const Node &leaf = **p;
if (!leaf.GetSpan().empty()) {
sourceRHSNodes.push_back(&leaf);
}
}
std::sort(sourceRHSNodes.begin(), sourceRHSNodes.end(), PartitionOrderComp);
// Build a mapping from target nodes to source-order indices, so that we
// can construct the Alignment object later.
std::map<const Node *, std::vector<int> > sourceOrder;
m_sourceRHS.reserve(sourceRHSNodes.size());
int srcIndex = 0;
for (std::vector<const Node *>::const_iterator p(sourceRHSNodes.begin());
p != sourceRHSNodes.end(); ++p, ++srcIndex) {
const Node &sinkNode = **p;
if (sinkNode.GetType() == TREE) {
m_sourceRHS.push_back(Symbol("X", NonTerminal));
sourceOrder[&sinkNode].push_back(srcIndex);
} else {
assert(sinkNode.GetType() == SOURCE);
m_sourceRHS.push_back(Symbol(sinkNode.GetLabel(), Terminal));
// Add all aligned target words to the sourceOrder map
const std::vector<Node *> &parents(sinkNode.GetParents());
for (std::vector<Node *>::const_iterator q(parents.begin());
q != parents.end(); ++q) {
if ((*q)->GetType() == TARGET) {
sourceOrder[*q].push_back(srcIndex);
}
}
}
}
// Target RHS + alignment
std::vector<const Node *> targetLeaves;
fragment.GetTargetLeaves(targetLeaves);
m_alignment.reserve(targetLeaves.size()); // might be too much but that's OK
m_targetRHS.reserve(targetLeaves.size());
for (std::vector<const Node *>::const_iterator p(targetLeaves.begin());
p != targetLeaves.end(); ++p) {
const Node &leaf = **p;
if (leaf.GetSpan().empty()) {
// The node doesn't cover any source words, so we can only add
// terminals to the target RHS (not a non-terminal).
std::vector<std::string> targetWords(leaf.GetTargetWords());
for (std::vector<std::string>::const_iterator q(targetWords.begin());
q != targetWords.end(); ++q) {
m_targetRHS.push_back(Symbol(*q, Terminal));
}
} else if (leaf.GetType() == SOURCE) {
// Do nothing
} else {
SymbolType type = (leaf.GetType() == TREE) ? NonTerminal : Terminal;
m_targetRHS.push_back(Symbol(leaf.GetLabel(), type));
int tgtIndex = m_targetRHS.size()-1;
std::map<const Node *, std::vector<int> >::iterator q(sourceOrder.find(&leaf));
assert(q != sourceOrder.end());
std::vector<int> &sourceNodes = q->second;
for (std::vector<int>::iterator r(sourceNodes.begin());
r != sourceNodes.end(); ++r) {
int srcIndex = *r;
m_alignment.push_back(std::make_pair(srcIndex, tgtIndex));
}
}
}
}
int ScfgRule::Scope() const
{
int scope = 0;
bool predIsNonTerm = false;
if (m_sourceRHS[0].GetType() == NonTerminal) {
++scope;
predIsNonTerm = true;
}
for (size_t i = 1; i < m_sourceRHS.size(); ++i) {
bool isNonTerm = m_sourceRHS[i].GetType() == NonTerminal;
if (isNonTerm && predIsNonTerm) {
++scope;
}
predIsNonTerm = isNonTerm;
}
if (predIsNonTerm) {
++scope;
}
return scope;
}
bool ScfgRule::PartitionOrderComp(const Node *a, const Node *b)
{
const Span &aSpan = a->GetSpan();
const Span &bSpan = b->GetSpan();
assert(!aSpan.empty() && !bSpan.empty());
return *(aSpan.begin()) < *(bSpan.begin());
}
} // namespace GHKM
} // namespace Moses
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