enable hot-word boosting

native_client/args.h

@@ -38,6 +38,8 @@ int json_candidate_transcripts = 3;
 
 int stream_size = 0;
 
+char* hot_words = NULL;
+
 void PrintHelp(const char* bin)
 {
     std::cout <<
@@ -56,6 +58,7 @@ void PrintHelp(const char* bin)
     "\t--json\t\t\t\tExtended output, shows word timings as JSON\n"
     "\t--candidate_transcripts NUMBER\tNumber of candidate transcripts to include in JSON output\n"
     "\t--stream size\t\t\tRun in stream mode, output intermediate results\n"
+    "\t--hot_words\t\t\tHot-words and their boosts. Word:Boost pairs are comma-separated\n"
     "\t--help\t\t\t\tShow help\n"
     "\t--version\t\t\tPrint version and exits\n";
     char* version = DS_Version();
@@ -66,7 +69,7 @@ void PrintHelp(const char* bin)
 
 bool ProcessArgs(int argc, char** argv)
 {
-    const char* const short_opts = "m:l:a:b:c:d:tejs:vh";
+    const char* const short_opts = "m:l:a:b:c:d:tejs:w:vh";
     const option long_opts[] = {
             {"model", required_argument, nullptr, 'm'},
             {"scorer", required_argument, nullptr, 'l'},
@@ -79,6 +82,7 @@ bool ProcessArgs(int argc, char** argv)
             {"json", no_argument, nullptr, 'j'},
             {"candidate_transcripts", required_argument, nullptr, 150},
             {"stream", required_argument, nullptr, 's'},
+            {"hot_words", required_argument, nullptr, 'w'},
             {"version", no_argument, nullptr, 'v'},
             {"help", no_argument, nullptr, 'h'},
             {nullptr, no_argument, nullptr, 0}
@@ -144,6 +148,10 @@ bool ProcessArgs(int argc, char** argv)
             has_versions = true;
             break;
 
+        case 'w':
+            hot_words = optarg;
+            break;
+
         case 'h': // -h or --help
         case '?': // Unrecognized option
         default:

native_client/client.cc

@@ -390,6 +390,22 @@ ProcessFile(ModelState* context, const char* path, bool show_times)
   }
 }
 
+std::vector<std::string>
+SplitStringOnDelim(std::string in_string, std::string delim)
+{
+  std::vector<std::string> out_vector;
+  char * tmp_str = new char[in_string.size() + 1];
+  std::copy(in_string.begin(), in_string.end(), tmp_str);
+  tmp_str[in_string.size()] = '\0';
+  const char* token = strtok(tmp_str, delim.c_str());
+  while( token != NULL ) {
+    out_vector.push_back(token);
+    token = strtok(NULL, delim.c_str());
+  }
+  delete[] tmp_str;
+  return out_vector;
+}
+
 int
 main(int argc, char **argv)
 {
@@ -432,6 +448,23 @@ main(int argc, char **argv)
   }
   // sphinx-doc: c_ref_model_stop
 
+  if (hot_words) {
+    std::vector<std::string> hot_words_ = SplitStringOnDelim(hot_words, ",");
+    for ( std::string hot_word_ : hot_words_ ) {
+      std::vector<std::string> pair_ = SplitStringOnDelim(hot_word_, ":");
+      const char* word = (pair_[0]).c_str();
+      // the strtof function will return 0 in case of non numeric characters
+      // so, check the boost string before we turn it into a float
+      bool boost_is_valid = (pair_[1].find_first_not_of("-.0123456789") == std::string::npos);
+      float boost = strtof((pair_[1]).c_str(),0);
+      status = DS_AddHotWord(ctx, word, boost);
+      if (status != 0 || !boost_is_valid) {
+        fprintf(stderr, "Could not enable hot-word.\n");
+        return 1;
+      }
+    }
+  }
+
 #ifndef NO_SOX
   // Initialise SOX
   assert(sox_init() == SOX_SUCCESS);

native_client/ctcdecode/__init__.py

@@ -96,6 +96,7 @@ def ctc_beam_search_decoder(probs_seq,
                             cutoff_prob=1.0,
                             cutoff_top_n=40,
                             scorer=None,
+                            hot_words=dict(),
                             num_results=1):
     """Wrapper for the CTC Beam Search Decoder.
 
@@ -116,6 +117,8 @@ def ctc_beam_search_decoder(probs_seq,
     :param scorer: External scorer for partially decoded sentence, e.g. word
                    count or language model.
     :type scorer: Scorer
+    :param hot_words: Map of words (keys) to their assigned boosts (values)
+    :type hot_words: map{string:float}
     :param num_results: Number of beams to return.
     :type num_results: int
     :return: List of tuples of confidence and sentence as decoding
@@ -124,7 +127,7 @@ def ctc_beam_search_decoder(probs_seq,
     """
     beam_results = swigwrapper.ctc_beam_search_decoder(
         probs_seq, alphabet, beam_size, cutoff_prob, cutoff_top_n,
-        scorer, num_results)
+        scorer, hot_words, num_results)
     beam_results = [(res.confidence, alphabet.Decode(res.tokens)) for res in beam_results]
     return beam_results
 
@@ -137,6 +140,7 @@ def ctc_beam_search_decoder_batch(probs_seq,
                                   cutoff_prob=1.0,
                                   cutoff_top_n=40,
                                   scorer=None,
+                                  hot_words=dict(),
                                   num_results=1):
     """Wrapper for the batched CTC beam search decoder.
 
@@ -161,13 +165,15 @@ def ctc_beam_search_decoder_batch(probs_seq,
     :param scorer: External scorer for partially decoded sentence, e.g. word
                    count or language model.
     :type scorer: Scorer
+    :param hot_words: Map of words (keys) to their assigned boosts (values)
+    :type hot_words: map{string:float}
     :param num_results: Number of beams to return.
     :type num_results: int
     :return: List of tuples of confidence and sentence as decoding
              results, in descending order of the confidence.
     :rtype: list
     """
-    batch_beam_results = swigwrapper.ctc_beam_search_decoder_batch(probs_seq, seq_lengths, alphabet, beam_size, num_processes, cutoff_prob, cutoff_top_n, scorer, num_results)
+    batch_beam_results = swigwrapper.ctc_beam_search_decoder_batch(probs_seq, seq_lengths, alphabet, beam_size, num_processes, cutoff_prob, cutoff_top_n, scorer, hot_words, num_results)
     batch_beam_results = [
         [(res.confidence, alphabet.Decode(res.tokens)) for res in beam_results]
         for beam_results in batch_beam_results

native_client/ctcdecode/ctc_beam_search_decoder.cpp

@@ -4,7 +4,7 @@
 #include <cmath>
 #include <iostream>
 #include <limits>
-#include <map>
+#include <unordered_map>
 #include <utility>
 
 #include "decoder_utils.h"
@@ -18,7 +18,8 @@ DecoderState::init(const Alphabet& alphabet,
                    size_t beam_size,
                    double cutoff_prob,
                    size_t cutoff_top_n,
-                   std::shared_ptr<Scorer> ext_scorer)
+                   std::shared_ptr<Scorer> ext_scorer,
+                   std::unordered_map<std::string, float> hot_words)
 {
   // assign special ids
   abs_time_step_ = 0;
@@ -29,6 +30,7 @@ DecoderState::init(const Alphabet& alphabet,
   cutoff_prob_ = cutoff_prob;
   cutoff_top_n_ = cutoff_top_n;
   ext_scorer_ = ext_scorer;
+  hot_words_ = hot_words;
   start_expanding_ = false;
 
   // init prefixes' root
@@ -160,8 +162,23 @@ DecoderState::next(const double *probs,
               float score = 0.0;
               std::vector<std::string> ngram;
               ngram = ext_scorer_->make_ngram(prefix_to_score);
+
+              float hot_boost = 0.0;
+              if (!hot_words_.empty()) {
+                std::unordered_map<std::string, float>::iterator iter;
+                // increase prob of prefix for every word
+                // that matches a word in the hot-words list
+                for (std::string word : ngram) {
+                  iter = hot_words_.find(word);
+                  if ( iter != hot_words_.end() ) {
+                    // increase the log_cond_prob(prefix|LM)
+                    hot_boost += iter->second;
+                  }
+                }
+              }
+
               bool bos = ngram.size() < ext_scorer_->get_max_order();
-              score = ext_scorer_->get_log_cond_prob(ngram, bos) * ext_scorer_->alpha;
+              score = ( ext_scorer_->get_log_cond_prob(ngram, bos) + hot_boost ) * ext_scorer_->alpha;
               log_p += score;
               log_p += ext_scorer_->beta;
             }
@@ -256,11 +273,12 @@ std::vector<Output> ctc_beam_search_decoder(
     double cutoff_prob,
     size_t cutoff_top_n,
     std::shared_ptr<Scorer> ext_scorer,
+    std::unordered_map<std::string, float> hot_words,
     size_t num_results)
 {
   VALID_CHECK_EQ(alphabet.GetSize()+1, class_dim, "Number of output classes in acoustic model does not match number of labels in the alphabet file. Alphabet file must be the same one that was used to train the acoustic model.");
   DecoderState state;
-  state.init(alphabet, beam_size, cutoff_prob, cutoff_top_n, ext_scorer);
+  state.init(alphabet, beam_size, cutoff_prob, cutoff_top_n, ext_scorer, hot_words);
   state.next(probs, time_dim, class_dim);
   return state.decode(num_results);
 }
@@ -279,6 +297,7 @@ ctc_beam_search_decoder_batch(
     double cutoff_prob,
     size_t cutoff_top_n,
     std::shared_ptr<Scorer> ext_scorer,
+    std::unordered_map<std::string, float> hot_words,
     size_t num_results)
 {
   VALID_CHECK_GT(num_processes, 0, "num_processes must be nonnegative!");
@@ -298,6 +317,7 @@ ctc_beam_search_decoder_batch(
                                   cutoff_prob,
                                   cutoff_top_n,
                                   ext_scorer,
+                                  hot_words,
                                   num_results));
   }
 

native_client/ctcdecode/ctc_beam_search_decoder.h

@@ -22,6 +22,7 @@ class DecoderState {
   std::vector<PathTrie*> prefixes_;
   std::unique_ptr<PathTrie> prefix_root_;
   TimestepTreeNode timestep_tree_root_{nullptr, 0};
+  std::unordered_map<std::string, float> hot_words_;
 
 public:
   DecoderState() = default;
@@ -48,7 +49,8 @@ class DecoderState {
            size_t beam_size,
            double cutoff_prob,
            size_t cutoff_top_n,
-           std::shared_ptr<Scorer> ext_scorer);
+           std::shared_ptr<Scorer> ext_scorer,
+           std::unordered_map<std::string, float> hot_words);
 
   /* Send data to the decoder
    *
@@ -88,6 +90,8 @@ class DecoderState {
  *     ext_scorer: External scorer to evaluate a prefix, which consists of
  *                 n-gram language model scoring and word insertion term.
  *                 Default null, decoding the input sample without scorer.
+ *     hot_words: A map of hot-words and their corresponding boosts
+ *                The hot-word is a string and the boost is a float.
  *     num_results: Number of beams to return.
  * Return:
  *     A vector where each element is a pair of score and decoding result,
@@ -103,6 +107,7 @@ std::vector<Output> ctc_beam_search_decoder(
     double cutoff_prob,
     size_t cutoff_top_n,
     std::shared_ptr<Scorer> ext_scorer,
+    std::unordered_map<std::string, float> hot_words,
     size_t num_results=1);
 
 /* CTC Beam Search Decoder for batch data
@@ -117,6 +122,8 @@ std::vector<Output> ctc_beam_search_decoder(
  *     ext_scorer: External scorer to evaluate a prefix, which consists of
  *                 n-gram language model scoring and word insertion term.
  *                 Default null, decoding the input sample without scorer.
+ *     hot_words: A map of hot-words and their corresponding boosts
+ *                The hot-word is a string and the boost is a float.
  *     num_results: Number of beams to return.
  * Return:
  *     A 2-D vector where each element is a vector of beam search decoding
@@ -136,6 +143,7 @@ ctc_beam_search_decoder_batch(
     double cutoff_prob,
     size_t cutoff_top_n,
     std::shared_ptr<Scorer> ext_scorer,
+    std::unordered_map<std::string, float> hot_words,
     size_t num_results=1);
 
 #endif  // CTC_BEAM_SEARCH_DECODER_H_

native_client/ctcdecode/swigwrapper.i

@@ -11,6 +11,7 @@
 %include <std_string.i>
 %include <std_vector.i>
 %include <std_shared_ptr.i>
+%include <std_unordered_map.i>
 %include "numpy.i"
 
 %init %{
@@ -22,6 +23,7 @@ namespace std {
     %template(UnsignedIntVector) vector<unsigned int>;
     %template(OutputVector) vector<Output>;
     %template(OutputVectorVector) vector<vector<Output>>;
+    %template(Map) unordered_map<string, float>;
 }
 
 %shared_ptr(Scorer);

native_client/deepspeech.cc

@@ -342,6 +342,53 @@ DS_EnableExternalScorer(ModelState* aCtx,
   return DS_ERR_OK;
 }
 
+int
+DS_AddHotWord(ModelState* aCtx,
+              const char* word,
+              float boost)
+{
+  if (aCtx->scorer_) {
+    const int size_before = aCtx->hot_words_.size();
+    aCtx->hot_words_.insert( std::pair<std::string,float> (word, boost) );
+    const int size_after = aCtx->hot_words_.size();
+    if (size_before == size_after) {
+      return DS_ERR_FAIL_INSERT_HOTWORD;
+    }
+    return DS_ERR_OK;
+  }
+  return DS_ERR_SCORER_NOT_ENABLED;
+}
+
+int
+DS_EraseHotWord(ModelState* aCtx,
+                const char* word)
+{
+  if (aCtx->scorer_) {
+    const int size_before = aCtx->hot_words_.size();
+    int err = aCtx->hot_words_.erase(word);
+    const int size_after = aCtx->hot_words_.size();
+    if (size_before == size_after) {
+      return DS_ERR_FAIL_ERASE_HOTWORD;
+    }
+    return DS_ERR_OK;
+  }
+  return DS_ERR_SCORER_NOT_ENABLED;
+}
+
+int
+DS_ClearHotWords(ModelState* aCtx)
+{
+  if (aCtx->scorer_) {
+    aCtx->hot_words_.clear();
+    const int size_after = aCtx->hot_words_.size();
+    if (size_after != 0) {
+      return DS_ERR_FAIL_CLEAR_HOTWORD;
+    }
+    return DS_ERR_OK;
+  }
+  return DS_ERR_SCORER_NOT_ENABLED;
+}
+
 int
 DS_DisableExternalScorer(ModelState* aCtx)
 {
@@ -390,7 +437,8 @@ DS_CreateStream(ModelState* aCtx,
                            aCtx->beam_width_,
                            cutoff_prob,
                            cutoff_top_n,
-                           aCtx->scorer_);
+                           aCtx->scorer_,
+                           aCtx->hot_words_);
 
   *retval = ctx.release();
   return DS_ERR_OK;