1 files changed, 91 insertions, 0 deletions
diff --git a/decoder/fst_translator.cc b/decoder/fst_translator.cc
new file mode 100644
index 00000000..38dbd717
--- /dev/null
+++ b/decoder/fst_translator.cc
@@ -0,0 +1,91 @@
+#include "translator.h"
+
+#include <sstream>
+#include <boost/shared_ptr.hpp>
+
+#include "sentence_metadata.h"
+#include "filelib.h"
+#include "hg.h"
+#include "hg_io.h"
+#include "earley_composer.h"
+#include "phrasetable_fst.h"
+#include "tdict.h"
+
+using namespace std;
+
+struct FSTTranslatorImpl {
+  FSTTranslatorImpl(const boost::program_options::variables_map& conf) :
+      goal_sym(conf["goal"].as<string>()),
+      kGOAL_RULE(new TRule("[Goal] ||| [" + goal_sym + ",1] ||| [1]")),
+      kGOAL(TD::Convert("Goal") * -1),
+      add_pass_through_rules(conf.count("add_pass_through_rules")) {
+    fst.reset(LoadTextPhrasetable(conf["grammar"].as<vector<string> >()));
+    ec.reset(new EarleyComposer(fst.get()));
+  }
+
+  bool Translate(const string& input,
+                 const vector<double>& weights,
+                 Hypergraph* forest) {
+    bool composed = false;
+    if (input.find("{\"rules\"") == 0) {
+      istringstream is(input);
+      Hypergraph src_cfg_hg;
+      assert(HypergraphIO::ReadFromJSON(&is, &src_cfg_hg));
+      if (add_pass_through_rules) {
+        SparseVector<double> feats;
+        feats.set_value(FD::Convert("PassThrough"), 1);
+        for (int i = 0; i < src_cfg_hg.edges_.size(); ++i) {
+          const vector<WordID>& f = src_cfg_hg.edges_[i].rule_->f_;
+          for (int j = 0; j < f.size(); ++j) {
+            if (f[j] > 0) {
+              fst->AddPassThroughTranslation(f[j], feats);
+            }
+          }
+        }
+      }
+      composed = ec->Compose(src_cfg_hg, forest);
+    } else {
+      const string dummy_grammar("[" + goal_sym + "] ||| " + input + " ||| TOP=1");
+      cerr << "  Dummy grammar: " << dummy_grammar << endl;
+      istringstream is(dummy_grammar);
+      if (add_pass_through_rules) {
+        vector<WordID> words;
+        TD::ConvertSentence(input, &words);
+        SparseVector<double> feats;
+        feats.set_value(FD::Convert("PassThrough"), 1);
+        for (int i = 0; i < words.size(); ++i)
+          fst->AddPassThroughTranslation(words[i], feats);
+      }
+      composed = ec->Compose(&is, forest);
+    }
+    if (composed) {
+      Hypergraph::TailNodeVector tail(1, forest->nodes_.size() - 1);
+      Hypergraph::Node* goal = forest->AddNode(TD::Convert("Goal")*-1);
+      Hypergraph::Edge* hg_edge = forest->AddEdge(kGOAL_RULE, tail);
+      forest->ConnectEdgeToHeadNode(hg_edge, goal);
+      forest->Reweight(weights);
+    }
+    if (add_pass_through_rules)
+      fst->ClearPassThroughTranslations();
+    return composed;
+  }
+
+  const string goal_sym;
+  const TRulePtr kGOAL_RULE;
+  const WordID kGOAL;
+  const bool add_pass_through_rules;
+  boost::shared_ptr<EarleyComposer> ec;
+  boost::shared_ptr<FSTNode> fst;
+};
+
+FSTTranslator::FSTTranslator(const boost::program_options::variables_map& conf) :
+  pimpl_(new FSTTranslatorImpl(conf)) {}
+
+bool FSTTranslator::TranslateImpl(const string& input,
+                              SentenceMetadata* smeta,
+                              const vector<double>& weights,
+                              Hypergraph* minus_lm_forest) {
+  smeta->SetSourceLength(0);  // don't know how to compute this
+  return pimpl_->Translate(input, weights, minus_lm_forest);
+}
+