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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 "ComposedRule.h"
#include "Node.h"
#include "Options.h"
#include "Subgraph.h"
#include <set>
#include <vector>
#include <queue>
namespace Moses {
namespace GHKM {
ComposedRule::ComposedRule(const Subgraph &baseRule)
: m_baseRule(baseRule)
, m_depth(baseRule.GetDepth())
, m_size(baseRule.GetSize())
, m_nodeCount(baseRule.GetNodeCount())
{
const std::set<const Node *> &leaves = baseRule.GetLeaves();
for (std::set<const Node *>::const_iterator p = leaves.begin();
p != leaves.end(); ++p) {
if ((*p)->GetType() == TREE) {
m_openAttachmentPoints.push(*p);
}
}
}
ComposedRule::ComposedRule(const ComposedRule &other, const Subgraph &rule,
int depth)
: m_baseRule(other.m_baseRule)
, m_attachedRules(other.m_attachedRules)
, m_openAttachmentPoints(other.m_openAttachmentPoints)
, m_depth(depth)
, m_size(other.m_size+rule.GetSize())
, m_nodeCount(other.m_nodeCount+rule.GetNodeCount()-1)
{
m_attachedRules.push_back(&rule);
m_openAttachmentPoints.pop();
}
const Node *ComposedRule::GetOpenAttachmentPoint()
{
return m_openAttachmentPoints.empty() ? 0 : m_openAttachmentPoints.front();
}
void ComposedRule::CloseAttachmentPoint()
{
assert(!m_openAttachmentPoints.empty());
m_attachedRules.push_back(0);
m_openAttachmentPoints.pop();
}
ComposedRule *ComposedRule::AttemptComposition(const Subgraph &rule,
const Options &options) const
{
// The smallest possible rule fragment should be rooted at a tree node.
// Note that this differs from the original GHKM definition.
assert(rule.GetRoot()->GetType() == TREE);
// Check the node count of the proposed rule.
if (m_nodeCount+rule.GetNodeCount()-1 > options.maxNodes) {
return 0;
}
// Check the size of the proposed rule.
if (m_size+rule.GetSize() > options.maxRuleSize) {
return 0;
}
// Determine the depth of the proposed rule and test whether it exceeds the
// limit.
int attachmentPointDepth = 0;
const Node *n = rule.GetRoot();
while (n != m_baseRule.GetRoot()) {
assert(n->GetParents().size() == 1);
n = n->GetParents()[0];
++attachmentPointDepth;
}
int newDepth = std::max(m_depth, attachmentPointDepth+rule.GetDepth());
if (newDepth > options.maxRuleDepth) {
return 0;
}
return new ComposedRule(*this, rule, newDepth);
}
Subgraph ComposedRule::CreateSubgraph()
{
std::set<const Node *> leaves;
const std::set<const Node *> &baseLeaves = m_baseRule.GetLeaves();
int i = 0;
for (std::set<const Node *>::const_iterator p = baseLeaves.begin();
p != baseLeaves.end(); ++p) {
const Node *baseLeaf = *p;
if (baseLeaf->GetType() == TREE && i < m_attachedRules.size()) {
const Subgraph *attachedRule = m_attachedRules[i++];
if (attachedRule) {
leaves.insert(attachedRule->GetLeaves().begin(),
attachedRule->GetLeaves().end());
continue;
}
}
leaves.insert(baseLeaf);
}
return Subgraph(m_baseRule.GetRoot(), leaves);
}
} // namespace GHKM
} // namespace Moses
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