Merge pull request #2184 from mozilla/fix-intermediate-decode

Fix for DS_IntermediateDecode modifying live prefixes in DecoderState

native_client/ctcdecode/ctc_beam_search_decoder.cpp

@@ -14,10 +14,11 @@
 
 using FSTMATCH = fst::SortedMatcher<fst::StdVectorFst>;
 
-DecoderState* decoder_init(const Alphabet &alphabet,
-                            int class_dim,
-                            Scorer* ext_scorer) {
-
+DecoderState*
+decoder_init(const Alphabet &alphabet,
+             int class_dim,
+             Scorer* ext_scorer)
+{
   // dimension check
   VALID_CHECK_EQ(class_dim, alphabet.GetSize()+1,
                  "The shape of probs does not match with "
@@ -47,16 +48,17 @@ DecoderState* decoder_init(const Alphabet &alphabet,
   return state;
 }
 
-void decoder_next(const double *probs,
-                  const Alphabet &alphabet,
-                  DecoderState *state,
-                  int time_dim,
-                  int class_dim,
-                  double cutoff_prob,
-                  size_t cutoff_top_n,
-                  size_t beam_size,
-                  Scorer *ext_scorer) {
-
+void
+decoder_next(const double *probs,
+             const Alphabet &alphabet,
+             DecoderState *state,
+             int time_dim,
+             int class_dim,
+             double cutoff_prob,
+             size_t cutoff_top_n,
+             size_t beam_size,
+             Scorer *ext_scorer)
+{
   // prefix search over time 
   for (size_t rel_time_step = 0; rel_time_step < time_dim; ++rel_time_step, ++state->time_step) {
     auto *prob = &probs[rel_time_step*class_dim];
@@ -155,39 +157,47 @@ void decoder_next(const double *probs,
   }  // end of loop over time
 }
 
-std::vector<Output> decoder_decode(DecoderState *state,
-                                   const Alphabet &alphabet,
-                                   size_t beam_size,
-                                   Scorer* ext_scorer) {
+std::vector<Output>
+decoder_decode(DecoderState *state,
+               const Alphabet &alphabet,
+               size_t beam_size,
+               Scorer* ext_scorer)
+{
+  std::vector<PathTrie*> prefixes_copy = state->prefixes;
+  std::unordered_map<const PathTrie*, float> scores;
+  for (PathTrie* prefix : prefixes_copy) {
+    scores[prefix] = prefix->score;
+  }
 
   // score the last word of each prefix that doesn't end with space
   if (ext_scorer != nullptr && !ext_scorer->is_character_based()) {
-    for (size_t i = 0; i < beam_size && i < state->prefixes.size(); ++i) {
-      auto prefix = state->prefixes[i];
+    for (size_t i = 0; i < beam_size && i < prefixes_copy.size(); ++i) {
+      auto prefix = prefixes_copy[i];
       if (!prefix->is_empty() && prefix->character != state->space_id) {
         float score = 0.0;
         std::vector<std::string> ngram = ext_scorer->make_ngram(prefix);
         score = ext_scorer->get_log_cond_prob(ngram) * ext_scorer->alpha;
         score += ext_scorer->beta;
-        prefix->score += score;
+        scores[prefix] += score;
       }
     }
   }
 
-  size_t num_prefixes = std::min(state->prefixes.size(), beam_size);
-  std::sort(state->prefixes.begin(), state->prefixes.begin() + num_prefixes, prefix_compare);
+  using namespace std::placeholders;
+  size_t num_prefixes = std::min(prefixes_copy.size(), beam_size);
+  std::sort(prefixes_copy.begin(), prefixes_copy.begin() + num_prefixes, std::bind(prefix_compare_external, _1, _2, scores));
 
   //TODO: expose this as an API parameter
   const int top_paths = 1;
 
   // compute aproximate ctc score as the return score, without affecting the
   // return order of decoding result. To delete when decoder gets stable.
-  for (size_t i = 0; i < top_paths && i < state->prefixes.size(); ++i) {
-    double approx_ctc = state->prefixes[i]->score;
+  for (size_t i = 0; i < top_paths && i < prefixes_copy.size(); ++i) {
+    double approx_ctc = scores[prefixes_copy[i]];
     if (ext_scorer != nullptr) {
       std::vector<int> output;
       std::vector<int> timesteps;
-      state->prefixes[i]->get_path_vec(output, timesteps);
+      prefixes_copy[i]->get_path_vec(output, timesteps);
       auto prefix_length = output.size();
       auto words = ext_scorer->split_labels(output);
       // remove word insert
@@ -195,10 +205,10 @@ std::vector<Output> decoder_decode(DecoderState *state,
       // remove language model weight:
       approx_ctc -= (ext_scorer->get_sent_log_prob(words)) * ext_scorer->alpha;
     }
-    state->prefixes[i]->approx_ctc = approx_ctc;
+    prefixes_copy[i]->approx_ctc = approx_ctc;
   }
 
-  return get_beam_search_result(state->prefixes, top_paths);
+  return get_beam_search_result(prefixes_copy, top_paths);
 }
 
 std::vector<Output> ctc_beam_search_decoder(

native_client/ctcdecode/decoder_utils.cpp

@@ -112,6 +112,18 @@ bool prefix_compare(const PathTrie *x, const PathTrie *y) {
   }
 }
 
+bool prefix_compare_external(const PathTrie *x, const PathTrie *y, const std::unordered_map<const PathTrie*, float>& scores) {
+  if (scores.at(x) == scores.at(y)) {
+    if (x->character == y->character) {
+      return false;
+    } else {
+      return (x->character < y->character);
+    }
+  } else {
+    return scores.at(x) > scores.at(y);
+  }
+}
+
 void add_word_to_fst(const std::vector<int> &word,
                      fst::StdVectorFst *dictionary) {
   if (dictionary->NumStates() == 0) {

native_client/ctcdecode/decoder_utils.h

@@ -67,6 +67,8 @@ std::vector<Output> get_beam_search_result(
 // Functor for prefix comparsion
 bool prefix_compare(const PathTrie *x, const PathTrie *y);
 
+bool prefix_compare_external(const PathTrie *x, const PathTrie *y, const std::unordered_map<const PathTrie*, float>& scores);
+
 /* Get length of utf8 encoding string
  * See: http://stackoverflow.com/a/4063229
  */

taskcluster/tc-cpp-ds-tests.sh

@@ -13,3 +13,5 @@ check_tensorflow_version
 run_all_inference_tests
 
 run_multi_inference_tests
+
+run_cpp_only_inference_tests

taskcluster/tc-tests-utils.sh

@@ -460,6 +460,15 @@ run_multi_inference_tests()
   assert_correct_multi_ldc93s1 "${multi_phrase_pbmodel_withlm}" "$status"
 }
 
+run_cpp_only_inference_tests()
+{
+  set +e
+  phrase_pbmodel_withlm_intermediate_decode=$(deepspeech --model ${TASKCLUSTER_TMP_DIR}/${model_name_mmap} --alphabet ${TASKCLUSTER_TMP_DIR}/alphabet.txt --lm ${TASKCLUSTER_TMP_DIR}/lm.binary --trie ${TASKCLUSTER_TMP_DIR}/trie --audio ${TASKCLUSTER_TMP_DIR}/LDC93S1.wav --stream 1280 2>${TASKCLUSTER_TMP_DIR}/stderr | tail -n 1)
+  status=$?
+  set -e
+  assert_correct_ldc93s1_lm "${phrase_pbmodel_withlm_intermediate_decode}" "$status"
+}
+
 android_run_tests()
 {
   cd ${DS_DSDIR}/native_client/java/