From 19e0a382269042605c347b48e5ac92c5012f1ccc Mon Sep 17 00:00:00 2001
From: Chris Dyer <cdyer@cs.cmu.edu>
Date: Thu, 10 Mar 2011 01:58:30 -0500
Subject: remove dependency on SRILM

---
 decoder/ff_csplit.cc | 93 +++++++++++++++++++++++-----------------------------
 1 file changed, 41 insertions(+), 52 deletions(-)

(limited to 'decoder/ff_csplit.cc')

diff --git a/decoder/ff_csplit.cc b/decoder/ff_csplit.cc
index 204b7ce6..dee6f4f9 100644
--- a/decoder/ff_csplit.cc
+++ b/decoder/ff_csplit.cc
@@ -3,8 +3,7 @@
 #include <set>
 #include <cstring>
 
-#include "Vocab.h"
-#include "Ngram.h"
+#include "klm/lm/model.hh"
 
 #include "sentence_metadata.h"
 #include "lattice.h"
@@ -155,51 +154,62 @@ void BasicCSplitFeatures::TraversalFeaturesImpl(
   pimpl_->TraversalFeaturesImpl(edge, smeta.GetSourceLattice().size(), features);
 }
 
+namespace {
+struct CSVMapper : public lm::ngram::EnumerateVocab {
+  CSVMapper(vector<lm::WordIndex>* out) : out_(out), kLM_UNKNOWN_TOKEN(0) { out_->clear(); }
+  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, kLM_UNKNOWN_TOKEN);
+    (*out_)[cdec_id] = index;
+  }
+  vector<lm::WordIndex>* out_;
+  const lm::WordIndex kLM_UNKNOWN_TOKEN;
+};
+}
+
+template<class Model>
 struct ReverseCharLMCSplitFeatureImpl {
-  ReverseCharLMCSplitFeatureImpl(const string& param) :
-      order_(5),
-      vocab_(TD::dict_),
-      ngram_(vocab_, order_) {
-    kBOS = vocab_.getIndex("<s>");
-    kEOS = vocab_.getIndex("</s>");
-    File file(param.c_str(), "r", 0);
-    assert(file);
-    cerr << "Reading " << order_ << "-gram LM from " << param << endl;
-    ngram_.read(file);
+  ReverseCharLMCSplitFeatureImpl(const string& param) {
+    CSVMapper vm(&cdec2klm_map_);
+    lm::ngram::Config conf;
+    conf.enumerate_vocab = &vm;
+    cerr << "Reading character LM from " << param << endl;
+    ngram_ = new Model(param.c_str(), conf);
+    order_ = ngram_->Order();
+    kEOS = MapWord(TD::Convert("</s>"));
+    assert(kEOS > 0);
+  }
+  lm::WordIndex MapWord(const WordID w) const {
+    if (w < cdec2klm_map_.size()) return cdec2klm_map_[w];
+    return 0;
   }
 
   double LeftPhonotacticProb(const Lattice& inword, const int start) {
     const int end = inword.size();
-    for (int i = 0; i < order_; ++i)
-      sc[i] = kBOS;
+    lm::ngram::State state = ngram_->BeginSentenceState();
     int sp = min(end - start, order_ - 1);
     // cerr << "[" << start << "," << sp << "]\n";
-    int ci = (order_ - sp - 1);
-    int wi = start;
+    int wi = start + sp - 1;
     while (sp > 0) {
-      sc[ci] = inword[wi][0].label;
-      // cerr << " CHAR: " << TD::Convert(sc[ci]) << "  ci=" << ci << endl;
-      ++wi;
-      ++ci;
+      const lm::ngram::State scopy(state);
+      ngram_->Score(scopy, MapWord(inword[wi][0].label), state);
+      --wi;
       --sp;
     }
-    // cerr << "  END ci=" << ci << endl;
-    sc[ci] = Vocab_None;
-    const double startprob = ngram_.wordProb(kEOS, sc);
-    // cerr << "  PROB=" << startprob << endl;
+    const lm::ngram::State scopy(state);
+    const double startprob = ngram_->Score(scopy, kEOS, state);
     return startprob;
   }
  private:
-  const int order_;
-  Vocab& vocab_;
-  VocabIndex kBOS;
-  VocabIndex kEOS;
-  Ngram ngram_;
-  VocabIndex sc[80];
+  Model* ngram_;
+  int order_;
+  vector<lm::WordIndex> cdec2klm_map_;
+  lm::WordIndex kEOS;
 };
 
 ReverseCharLMCSplitFeature::ReverseCharLMCSplitFeature(const string& param) :
-  pimpl_(new ReverseCharLMCSplitFeatureImpl(param)),
+  pimpl_(new ReverseCharLMCSplitFeatureImpl<lm::ngram::ProbingModel>(param)),
   fid_(FD::Convert("RevCharLM")) {}
 
 void ReverseCharLMCSplitFeature::TraversalFeaturesImpl(
@@ -217,26 +227,5 @@ void ReverseCharLMCSplitFeature::TraversalFeaturesImpl(
   if (edge.rule_->EWords() != 1) return;
   const double lpp = pimpl_->LeftPhonotacticProb(smeta.GetSourceLattice(), edge.i_);
   features->set_value(fid_, lpp);
-#if 0
-  WordID neighbor_word = 0;
-  const WordID word = edge.rule_->e_[1];
-  const char* sword = TD::Convert(word);
-  const int len = strlen(sword);
-  int cur = 0;
-  int chars = 0;
-  while(cur < len) {
-    cur += UTF8Len(sword[cur]);
-    ++chars;
-  }
-  if (chars > 4 && (sword[0] == 's' || sword[0] == 'n')) {
-    neighbor_word = TD::Convert(string(&sword[1]));
-  }
-  if (neighbor_word) {
-    float nfreq = freq_dict_.LookUp(neighbor_word);
-    cerr << "COMPARE: " << TD::Convert(word) << " & " << TD::Convert(neighbor_word) << endl;
-    if (!nfreq) nfreq = 99.0f;
-    features->set_value(fdoes_deletion_help_, (freq - nfreq));
-  }
-#endif
 }
 
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