1 files changed, 115 insertions, 0 deletions
diff --git a/klm/lm/sri.cc b/klm/lm/sri.cc
new file mode 100644
index 00000000..7bd23d76
--- /dev/null
+++ b/klm/lm/sri.cc
@@ -0,0 +1,115 @@
+#include "lm/exception.hh"
+#include "lm/sri.hh"
+
+#include <Ngram.h>
+#include <Vocab.h>
+
+#include <errno.h>
+
+namespace lm {
+namespace sri {
+
+Vocabulary::Vocabulary() : sri_(new Vocab) {}
+
+Vocabulary::~Vocabulary() {}
+
+WordIndex Vocabulary::Index(const char *str) const {
+  WordIndex ret = sri_->getIndex(str);
+  // NGram wants the index of Vocab_Unknown for unknown words, but for some reason SRI returns Vocab_None here :-(.
+  if (ret == Vocab_None) {
+    return not_found_;
+  } else {
+    return ret;
+  }
+}
+
+const char *Vocabulary::Word(WordIndex index) const {
+  return sri_->getWord(index);
+}
+
+void Vocabulary::FinishedLoading() {
+  SetSpecial(
+    sri_->ssIndex(),
+    sri_->seIndex(),
+    sri_->unkIndex(),
+    sri_->highIndex() + 1);
+}
+
+namespace {
+Ngram *MakeSRIModel(const char *file_name, unsigned int ngram_length, Vocab &sri_vocab) {
+  sri_vocab.unkIsWord() = true;
+  std::auto_ptr<Ngram> ret(new Ngram(sri_vocab, ngram_length));
+  File file(file_name, "r");
+  errno = 0;
+  if (!ret->read(file)) {
+    UTIL_THROW(FormatLoadException, "reading file " << file_name << " with SRI failed.");
+  }
+  return ret.release();
+}
+} // namespace
+
+Model::Model(const char *file_name, unsigned int ngram_length) : sri_(MakeSRIModel(file_name, ngram_length, *vocab_.sri_)) {
+  if (!sri_->setorder()) {
+    UTIL_THROW(FormatLoadException, "Can't have an SRI model with order 0.");
+  }
+  vocab_.FinishedLoading();
+  State begin_state = State();
+  begin_state.valid_length_ = 1;
+  if (kMaxOrder > 1) {
+    begin_state.history_[0] = vocab_.BeginSentence();
+    if (kMaxOrder > 2) begin_state.history_[1] = Vocab_None;
+  }
+  State null_state = State();
+  null_state.valid_length_ = 0;
+  if (kMaxOrder > 1) null_state.history_[0] = Vocab_None;
+  Init(begin_state, null_state, vocab_, sri_->setorder());
+  not_found_ = vocab_.NotFound();
+}
+
+Model::~Model() {}
+
+namespace {
+
+/* Argh SRI's wordProb knows the ngram length but doesn't return it.  One more
+ * reason you should use my model.  */
+// TODO(stolcke): fix SRILM so I don't have to do this.   
+unsigned int MatchedLength(Ngram &model, const WordIndex new_word, const SRIVocabIndex *const_history) {
+  unsigned int out_length = 0;
+  // This gets the length of context used, which is ngram_length - 1 unless new_word is OOV in which case it is 0.
+  model.contextID(new_word, const_history, out_length);
+  return out_length + 1;
+}
+
+} // namespace
+
+FullScoreReturn Model::FullScore(const State &in_state, const WordIndex new_word, State &out_state) const {
+  // If you get a compiler in this function, change SRIVocabIndex in sri.hh to match the one found in SRI's Vocab.h.
+  const SRIVocabIndex *const_history;
+  SRIVocabIndex local_history[Order()];
+  if (in_state.valid_length_ < kMaxOrder - 1) {
+    const_history = in_state.history_;
+  } else {
+    std::copy(in_state.history_, in_state.history_ + in_state.valid_length_, local_history);
+    local_history[in_state.valid_length_] = Vocab_None;
+    const_history = local_history;
+  }
+  FullScoreReturn ret;
+  if (new_word != not_found_) {
+    ret.ngram_length = MatchedLength(*sri_, new_word, const_history);
+    out_state.history_[0] = new_word;
+    out_state.valid_length_ = std::min<unsigned char>(ret.ngram_length, Order() - 1);
+    std::copy(const_history, const_history + out_state.valid_length_ - 1, out_state.history_ + 1);
+    if (out_state.valid_length_ < kMaxOrder - 1) {
+      out_state.history_[out_state.valid_length_] = Vocab_None;
+    }
+  } else {
+    ret.ngram_length = 0;
+    if (kMaxOrder > 1) out_state.history_[0] = Vocab_None;
+    out_state.valid_length_ = 0;
+  }
+  ret.prob = sri_->wordProb(new_word, const_history);
+  return ret;
+}
+
+} // namespace sri
+} // namespace lm