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ChartKBestExtractor: fix memory leak, clean-up code

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This commit is contained in:
Phil Williams 2014-04-19 10:29:41 +01:00
parent 00a2bd395a
commit 568685cb66
2 changed files with 124 additions and 99 deletions
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154
moses/ChartKBestExtractor.cpp
View File

@ -32,52 +32,48 @@ namespace Moses
// Extract the k-best list from the search graph.
void ChartKBestExtractor::Extract(
const std::vector<const ChartHypothesis*> &topHypos, std::size_t k,
const std::vector<const ChartHypothesis*> &topLevelHypos, std::size_t k,
KBestVec &kBestList)
{
typedef std::vector<const ChartHypothesis*> HypoVec;
kBestList.clear();
if (topHypos.empty()) {
if (topLevelHypos.empty()) {
return;
}
// Create a new top-level ChartHypothesis that has the best hypothesis as its
// predecessor. This is the search hypergraph's target vertex.
HypoVec::const_iterator iter = topHypos.begin();
// Create a new ChartHypothesis object, supremeHypo, that has the best
// top-level hypothesis as its predecessor and has the same score.
std::vector<const ChartHypothesis*>::const_iterator p = topLevelHypos.begin();
const ChartHypothesis &bestTopLevelHypo = **p;
boost::scoped_ptr<ChartHypothesis> supremeHypo(
new ChartHypothesis(**iter, *this));
new ChartHypothesis(bestTopLevelHypo, *this));
// Do the same for each alternative top-level hypothesis, but add the new
// ChartHypothesis objects as arcs from supremeHypo, as if they had been
// recombined.
float prevScore = (*iter)->GetTotalScore();
for (++iter; iter != topHypos.end(); ++iter) {
// Check that the first item in topHypos really was the best.
UTIL_THROW_IF2((*iter)->GetTotalScore() <= prevScore,
"top-level vertices are not correctly sorted");
for (++p; p != topLevelHypos.end(); ++p) {
// Check that the first item in topLevelHypos really was the best.
UTIL_THROW_IF2((*p)->GetTotalScore() <= bestTopLevelHypo.GetTotalScore(),
"top-level hypotheses are not correctly sorted");
// Note: there's no need for a smart pointer here: supremeHypo will take
// ownership of altHypo.
ChartHypothesis *altHypo = new ChartHypothesis(**iter, *this);
ChartHypothesis *altHypo = new ChartHypothesis(**p, *this);
supremeHypo->AddArc(altHypo);
}
// Create the target vertex corresponding to supremeHypo then generate
// it's k-best list.
boost::shared_ptr<Vertex> top = FindOrCreateVertex(*supremeHypo);
LazyKthBest(*top, k, k);
// Create the target vertex then lazily fill its k-best list.
boost::shared_ptr<Vertex> targetVertex = FindOrCreateVertex(*supremeHypo);
LazyKthBest(*targetVertex, k, k);
// Copy the k-best list from the target vertex, but drop the top edge from
// each derivation.
kBestList.reserve(top->kBestList.size());
for (KBestVec::const_iterator p = top->kBestList.begin();
p != top->kBestList.end(); ++p) {
const Derivation &d = **p;
assert(d.edge.tail.size() == 1); // d should have exactly one predecessor.
assert(d.backPointers.size() == 1);
std::size_t i = d.backPointers[0];
boost::shared_ptr<Derivation> pred = d.edge.tail[0]->kBestList[i];
kBestList.push_back(pred);
kBestList.reserve(targetVertex->kBestList.size());
for (std::vector<boost::weak_ptr<Derivation> >::const_iterator
q = targetVertex->kBestList.begin();
q != targetVertex->kBestList.end(); ++q) {
const boost::shared_ptr<Derivation> d(*q);
assert(d);
assert(d->subderivations.size() == 1);
kBestList.push_back(d->subderivations[0]);
}
}
@ -96,8 +92,7 @@ Phrase ChartKBestExtractor::GetOutputPhrase(const Derivation &d)
const Word &word = phrase.GetWord(pos);
if (word.IsNonTerminal()) {
std::size_t nonTermInd = nonTermIndexMap[pos];
const Derivation &subderivation =
*d.edge.tail[nonTermInd]->kBestList[d.backPointers[nonTermInd]];
const Derivation &subderivation = *d.subderivations[nonTermInd];
Phrase subPhrase = GetOutputPhrase(subderivation);
ret.Append(subPhrase);
} else {
@ -142,26 +137,6 @@ ChartKBestExtractor::UnweightedHyperarc ChartKBestExtractor::CreateEdge(
return edge;
}
void ChartKBestExtractor::GetCandidates(Vertex &v, std::size_t k)
{
// Create a derivation for v's best incoming edge.
UnweightedHyperarc bestEdge = CreateEdge(v.hypothesis);
boost::shared_ptr<Derivation> d(new Derivation(bestEdge));
v.candidates.push(d);
v.seen.insert(d);
// Create derivations for the rest of v's incoming edges.
const ChartArcList *arcList = v.hypothesis.GetArcList();
if (arcList) {
for (std::size_t i = 0; i < arcList->size(); ++i) {
const ChartHypothesis &recombinedHypo = *(*arcList)[i];
UnweightedHyperarc edge = CreateEdge(recombinedHypo);
boost::shared_ptr<Derivation> d(new Derivation(edge));
v.candidates.push(d);
v.seen.insert(d);
}
}
}
// Look for the vertex corresponding to a given ChartHypothesis, creating
// a new one if necessary.
boost::shared_ptr<ChartKBestExtractor::Vertex>
@ -174,14 +149,51 @@ ChartKBestExtractor::FindOrCreateVertex(const ChartHypothesis &h)
return sp; // Vertex was already in m_vertexMap.
}
sp.reset(new Vertex(h));
// Create the 1-best derivation and add it to the vertex's kBestList.
UnweightedHyperarc bestEdge;
bestEdge.head = sp;
const std::vector<const ChartHypothesis*> &prevHypos = h.GetPrevHypos();
bestEdge.tail.resize(prevHypos.size());
for (std::size_t i = 0; i < prevHypos.size(); ++i) {
const ChartHypothesis *prevHypo = prevHypos[i];
bestEdge.tail[i] = FindOrCreateVertex(*prevHypo);
}
boost::shared_ptr<Derivation> bestDerivation(new Derivation(bestEdge));
std::pair<DerivationSet::iterator, bool> q =
m_derivations.insert(bestDerivation);
assert(q.second);
sp->kBestList.push_back(bestDerivation);
return sp;
}
// Create the 1-best derivation for each edge in BS(v) (except the best one)
// and add it to v's candidate queue.
void ChartKBestExtractor::GetCandidates(Vertex &v, std::size_t k)
{
// Create derivations for all of v's incoming edges except the best. This
// means everything in v.hypothesis.GetArcList() and not the edge defined
// by v.hypothesis itself. The 1-best derivation for that edge will already
// have been created.
const ChartArcList *arcList = v.hypothesis.GetArcList();
if (arcList) {
for (std::size_t i = 0; i < arcList->size(); ++i) {
const ChartHypothesis &recombinedHypo = *(*arcList)[i];
boost::shared_ptr<Vertex> w = FindOrCreateVertex(recombinedHypo);
assert(w->kBestList.size() == 1);
v.candidates.push(w->kBestList[0]);
}
}
}
// Lazily fill v's k-best list.
void ChartKBestExtractor::LazyKthBest(Vertex &v, std::size_t k,
std::size_t globalK)
{
// If this is the first visit to vertex v then initialize the priority queue.
if (v.visited == false) {
// The 1-best derivation should already be in v's k-best list.
assert(v.kBestList.size() == 1);
// Initialize v's priority queue.
GetCandidates(v, globalK);
v.visited = true;
}
@ -191,49 +203,57 @@ void ChartKBestExtractor::LazyKthBest(Vertex &v, std::size_t k,
if (!v.kBestList.empty()) {
// Update the priority queue by adding the successors of the last
// derivation (unless they've been seen before).
const Derivation &d = *v.kBestList.back();
LazyNext(v, d, globalK);
boost::shared_ptr<Derivation> d(v.kBestList.back());
LazyNext(v, *d, globalK);
}
// Check if there are any derivations left in the queue.
if (v.candidates.empty()) {
break;
}
// Get the next best derivation and delete it from the queue.
boost::shared_ptr<Derivation> d = v.candidates.top();
boost::weak_ptr<Derivation> d = v.candidates.top();
v.candidates.pop();
// Add it to the k-best list.
v.kBestList.push_back(d);
}
}
// Create the neighbours of Derivation d and add them to v's candidate queue.
void ChartKBestExtractor::LazyNext(Vertex &v, const Derivation &d,
std::size_t globalK)
{
// Create the neighbours of Derivation d.
for (std::size_t i = 0; i < d.backPointers.size(); ++i) {
Vertex &predVertex = *d.edge.tail[i];
// Ensure that predVertex's k-best list contains enough derivations.
for (std::size_t i = 0; i < d.edge.tail.size(); ++i) {
Vertex &pred = *d.edge.tail[i];
// Ensure that pred's k-best list contains enough derivations.
std::size_t k = d.backPointers[i] + 2;
LazyKthBest(predVertex, k, globalK);
if (predVertex.kBestList.size() < k) {
// predVertex's derivations have been exhausted.
LazyKthBest(pred, k, globalK);
if (pred.kBestList.size() < k) {
// pred's derivations have been exhausted.
continue;
}
// Create the neighbour.
boost::shared_ptr<Derivation> next(new Derivation(d, i));
// Check if it has been created before.
std::pair<Vertex::DerivationSet::iterator, bool> p = v.seen.insert(next);
std::pair<DerivationSet::iterator, bool> p = m_derivations.insert(next);
if (p.second) {
v.candidates.push(next); // Haven't previously seen it.
}
}
}
// Construct a Derivation corresponding to a ChartHypothesis.
// Construct the 1-best Derivation that ends at edge e.
ChartKBestExtractor::Derivation::Derivation(const UnweightedHyperarc &e)
{
edge = e;
backPointers.resize(edge.tail.size(), 0);
std::size_t arity = edge.tail.size();
backPointers.resize(arity, 0);
subderivations.reserve(arity);
for (std::size_t i = 0; i < arity; ++i) {
const Vertex &pred = *edge.tail[i];
assert(pred.kBestList.size() == 1);
boost::shared_ptr<Derivation> sub(pred.kBestList[0]);
subderivations.push_back(sub);
}
scoreBreakdown = edge.head->hypothesis.GetScoreBreakdown();
score = edge.head->hypothesis.GetTotalScore();
}
@ -244,14 +264,16 @@ ChartKBestExtractor::Derivation::Derivation(const Derivation &d, std::size_t i)
edge.head = d.edge.head;
edge.tail = d.edge.tail;
backPointers = d.backPointers;
subderivations = d.subderivations;
std::size_t j = ++backPointers[i];
scoreBreakdown = d.scoreBreakdown;
// Deduct the score of the old subderivation.
const Derivation &oldSubderivation = *(edge.tail[i]->kBestList[j-1]);
scoreBreakdown.MinusEquals(oldSubderivation.scoreBreakdown);
scoreBreakdown.MinusEquals(subderivations[i]->scoreBreakdown);
// Update the subderivation pointer.
boost::shared_ptr<Derivation> newSub(edge.tail[i]->kBestList[j]);
subderivations[i] = newSub;
// Add the score of the new subderivation.
const Derivation &newSubderivation = *(edge.tail[i]->kBestList[j]);
scoreBreakdown.PlusEquals(newSubderivation.scoreBreakdown);
scoreBreakdown.PlusEquals(subderivations[i]->scoreBreakdown);
score = scoreBreakdown.GetWeightedScore();
}

69
moses/ChartKBestExtractor.h
View File

@ -24,6 +24,7 @@
#include "ScoreComponentCollection.h"
#include <boost/unordered_set.hpp>
#include <boost/weak_ptr.hpp>
#include <queue>
#include <vector>
@ -53,17 +54,46 @@ public:
UnweightedHyperarc edge;
std::vector<std::size_t> backPointers;
std::vector<boost::shared_ptr<Derivation> > subderivations;
ScoreComponentCollection scoreBreakdown;
float score;
};
struct DerivationOrderer {
bool operator()(const boost::shared_ptr<Derivation> &d1,
const boost::shared_ptr<Derivation> &d2) const {
return d1->score < d2->score;
bool operator()(const boost::weak_ptr<Derivation> &d1,
const boost::weak_ptr<Derivation> &d2) const {
boost::shared_ptr<Derivation> s1(d1);
boost::shared_ptr<Derivation> s2(d2);
return s1->score < s2->score;
}
};
struct Vertex {
typedef std::priority_queue<boost::weak_ptr<Derivation>,
std::vector<boost::weak_ptr<Derivation> >,
DerivationOrderer> DerivationQueue;
Vertex(const ChartHypothesis &h) : hypothesis(h), visited(false) {}
const ChartHypothesis &hypothesis;
std::vector<boost::weak_ptr<Derivation> > kBestList;
DerivationQueue candidates;
bool visited;
};
typedef std::vector<boost::shared_ptr<Derivation> > KBestVec;
// Extract the k-best list from the search hypergraph given the full, sorted
// list of top-level vertices.
void Extract(const std::vector<const ChartHypothesis*> &topHypos,
std::size_t k, KBestVec &);
static Phrase GetOutputPhrase(const Derivation &);
private:
typedef boost::unordered_map<const ChartHypothesis *,
boost::shared_ptr<Vertex> > VertexMap;
struct DerivationHasher {
std::size_t operator()(const boost::shared_ptr<Derivation> &d) const {
std::size_t seed = 0;
@ -83,36 +113,8 @@ public:
}
};
struct Vertex {
typedef std::priority_queue<boost::shared_ptr<Derivation>,
std::vector<boost::shared_ptr<Derivation> >,
DerivationOrderer> DerivationQueue;
typedef boost::unordered_set<boost::shared_ptr<Derivation>,
DerivationHasher,
DerivationEqualityPred> DerivationSet;
Vertex(const ChartHypothesis &h) : hypothesis(h), visited(false) {}
const ChartHypothesis &hypothesis;
std::vector<boost::shared_ptr<Derivation> > kBestList;
DerivationQueue candidates;
DerivationSet seen;
bool visited;
};
typedef std::vector<boost::shared_ptr<Derivation> > KBestVec;
// Extract the k-best list from the search hypergraph given the full, sorted
// list of top-level vertices.
void Extract(const std::vector<const ChartHypothesis*> &topHypos,
std::size_t k, KBestVec &);
static Phrase GetOutputPhrase(const Derivation &);
private:
typedef boost::unordered_map<const ChartHypothesis *,
boost::shared_ptr<Vertex> > VertexMap;
typedef boost::unordered_set<boost::shared_ptr<Derivation>, DerivationHasher,
DerivationEqualityPred> DerivationSet;
UnweightedHyperarc CreateEdge(const ChartHypothesis &);
boost::shared_ptr<Vertex> FindOrCreateVertex(const ChartHypothesis &);
@ -121,6 +123,7 @@ private:
void LazyNext(Vertex &, const Derivation &, std::size_t);
VertexMap m_vertexMap;
DerivationSet m_derivations;
};
} // namespace Moses