From f794c881ccaf4aa0646300dea1e1f6e7a307e019 Mon Sep 17 00:00:00 2001
From: Kenneth Heafield <github@kheafield.com>
Date: Wed, 12 Sep 2012 18:36:03 +0100
Subject: Partially written bridge to lazy

---
 decoder/lazy.cc | 122 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 decoder/lazy.h  |   8 ++++
 2 files changed, 130 insertions(+)
 create mode 100644 decoder/lazy.cc
 create mode 100644 decoder/lazy.h

(limited to 'decoder')

diff --git a/decoder/lazy.cc b/decoder/lazy.cc
new file mode 100644
index 00000000..f5b61c75
--- /dev/null
+++ b/decoder/lazy.cc
@@ -0,0 +1,122 @@
+#include "hg.h"
+#include "lazy.h"
+#include "tdict.h"
+
+#include "lm/enumerate_vocab.hh"
+#include "lm/model.hh"
+#include "search/edge.hh"
+#include "search/vertex.hh"
+#include "util/exception.hh"
+
+#include <boost/scoped_array.hpp>
+
+namespace {
+
+struct MapVocab : public lm::EnumerateVocab {
+  public:
+    MapVocab() {}
+
+    // Do not call after Lookup.  
+    void Add(lm::WordIndex index, const StringPiece &str) {
+      const WordID cdec_id = TD::Convert(str.as_string());
+      if (cdec_id >= out_->size()) out_.resize(cdec_id + 1);
+      out_[cdec_id] = index;
+    }
+
+    // Assumes Add has been called and will never be called again.  
+    lm::WordIndex FromCDec(WordID id) const {
+      return out_[out.size() > id ? id : 0];
+    }
+
+  private:
+    std::vector<lm::WordIndex> out_;
+};
+
+class LazyBase {
+  public:
+    LazyBase() {}
+
+    virtual ~LazyBase() {}
+
+    virtual void Search(const Hypergraph &hg) const = 0;
+
+    static LazyBase *Load(const char *model_file);
+
+  protected:
+    lm::ngram::Config GetConfig() const {
+      lm::ngram::Config ret;
+      ret.enumerate_vocab = &vocab_;
+      return ret;
+    }
+
+    MapVocab vocab_;
+};
+
+template <class Model> class Lazy : public LazyBase {
+  public:
+    explicit Lazy(const char *model_file) : m_(model_file, GetConfig()) {}
+
+    void Search(const Hypergraph &hg) const;
+
+  private:
+    void ConvertEdge(const Context<Model> &context, bool final, search::Vertex *vertices, const Hypergraph::Edge &in, search::Edge &out) const;
+
+    const Model m_;
+};
+
+static LazyBase *LazyBase::Load(const char *model_file) {
+  lm::ngram::ModelType model_type;
+  if (!lm::ngram::RecognizeBinary(lm_name, model_type)) model_type = lm::ngram::PROBING;
+  switch (model_type) {
+    case lm::ngram::PROBING:
+      return new Lazy<lm::ngram::ProbingModel>(model_file);
+    case lm::ngram::REST_PROBING:
+      return new Lazy<lm::ngram::RestProbingModel>(model_file);
+    default:
+      UTIL_THROW(util::Exception, "Sorry this lm type isn't supported yet.");
+  }
+}
+
+template <class Model> void Lazy<Model>::Search(const Hypergraph &hg) const {
+  boost::scoped_array<search::Vertex> out_vertices(new search::Vertex[hg.nodes_.size()]);
+  boost::scoped_array<search::Edge> out_edges(new search::Edge[hg.edges_.size()]);
+  for (unsigned int i = 0; i < hg.nodes_.size(); ++i) {
+    search::Vertex *out_vertex = out_vertices[i];
+    const Hypergraph::EdgesVector &down_edges = hg.nodes_[i].in_edges_;
+    for (unsigned int j = 0; j < edges.size(); ++j) {
+      unsigned int edge_index = down_edges[j];
+      const Hypergraph::Edge &in_edge = hg.edges_[edge_index];
+      search::Edge &out_edge = out_edges[edge_index];
+    }
+  }
+}
+
+// TODO: get weights into here somehow.  
+template <class Model> void Lazy<Model>::ConvertEdge(const Context<Model> &context, bool final, search::Vertices *vertices, const Hypergraph::Edge &in, search::Edge &out) const {
+  const std::vector<WordID> &e = in_edge.rule_->e();
+  std::vector<lm::WordIndex> words;
+  unsigned int terminals = 0;
+  for (std::vector<WordID>::const_iterator word = e.begin(); word != e.end(); ++word) {
+    if (*word <= 0) {
+      out.Add(vertices[edge.tail_nodes_[-*word]]);
+      words.push_back(lm::kMaxWordIndex);
+    } else {
+      ++terminals;
+      words.push_back(vocab_.FromCDec(*word));
+    }
+  }
+
+  if (final) {
+    words.push_back(m_.GetVocabulary().EndSentence());
+  }
+
+  float additive = edge.rule_->GetFeatureValues().dot(weight_vector);
+
+  out.InitRule().Init(context, additive, words, final);
+}
+
+} // namespace
+
+void PassToLazy(const Hypergraph &hg) {
+
+}
diff --git a/decoder/lazy.h b/decoder/lazy.h
new file mode 100644
index 00000000..aecd030d
--- /dev/null
+++ b/decoder/lazy.h
@@ -0,0 +1,8 @@
+#ifndef _LAZY_H_
+#define _LAZY_H_
+
+class Hypergraph;
+
+void PassToLazy(const Hypergraph &hg);
+
+#endif // _LAZY_H_
-- 
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