Restored old CTC decoder API

native_client/ctcdecode/ctc_beam_search_decoder.cpp

@@ -196,3 +196,62 @@ std::vector<Output> decoder_decode(DecoderState *state,
 
   return get_beam_search_result(state->prefixes, beam_size);
 }
+
+
+std::vector<Output> ctc_beam_search_decoder(
+    const double *probs,
+    int time_dim,
+    int class_dim,
+    const Alphabet &alphabet,
+    size_t beam_size,
+    double cutoff_prob,
+    size_t cutoff_top_n,
+    Scorer *ext_scorer) {
+
+  DecoderState *state = decoder_init(alphabet, class_dim, ext_scorer);
+
+  decoder_next(probs, alphabet, state, time_dim, class_dim, cutoff_prob, cutoff_top_n, beam_size, ext_scorer);
+
+  return decoder_decode(state, alphabet, beam_size, ext_scorer);
+}
+
+std::vector<std::vector<Output>>
+ctc_beam_search_decoder_batch(
+    const double *probs,
+    int batch_size,
+    int time_dim,
+    int class_dim,
+    const int* seq_lengths,
+    int seq_lengths_size,
+    const Alphabet &alphabet,
+    size_t beam_size,
+    size_t num_processes,
+    double cutoff_prob,
+    size_t cutoff_top_n,
+    Scorer *ext_scorer) {
+  VALID_CHECK_GT(num_processes, 0, "num_processes must be nonnegative!");
+  VALID_CHECK_EQ(batch_size, seq_lengths_size, "must have one sequence length per batch element");
+  // thread pool
+  ThreadPool pool(num_processes);
+
+  // enqueue the tasks of decoding
+  std::vector<std::future<std::vector<Output>>> res;
+  for (size_t i = 0; i < batch_size; ++i) {
+    res.emplace_back(pool.enqueue(ctc_beam_search_decoder,
+                                  &probs[i*time_dim*class_dim],
+                                  seq_lengths[i],
+                                  class_dim,
+                                  alphabet,
+                                  beam_size,
+                                  cutoff_prob,
+                                  cutoff_top_n,
+                                  ext_scorer));
+  }
+
+  // get decoding results
+  std::vector<std::vector<Output>> batch_results;
+  for (size_t i = 0; i < batch_size; ++i) {
+    batch_results.emplace_back(res[i].get());
+  }
+  return batch_results;
+}

native_client/ctcdecode/ctc_beam_search_decoder.h

@@ -68,4 +68,63 @@ std::vector<Output> decoder_decode(DecoderState *state,
                                    size_t beam_size,
                                    Scorer* ext_scorer);
 
+/* CTC Beam Search Decoder
+ * Parameters:
+ *     probs: 2-D vector where each element is a vector of probabilities
+ *            over alphabet of one time step.
+ *     time_dim: Number of timesteps.
+ *     class_dim: Alphabet length (plus 1 for space character).
+ *     alphabet: The alphabet.
+ *     beam_size: The width of beam search.
+ *     cutoff_prob: Cutoff probability for pruning.
+ *     cutoff_top_n: Cutoff number for pruning.
+ *     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.
+ * Return:
+ *     A vector where each element is a pair of score and decoding result,
+ *     in descending order.
+*/
+
+std::vector<Output> ctc_beam_search_decoder(
+    const double* probs,
+    int time_dim,
+    int class_dim,
+    const Alphabet &alphabet,
+    size_t beam_size,
+    double cutoff_prob,
+    size_t cutoff_top_n,
+    Scorer *ext_scorer);
+
+/* CTC Beam Search Decoder for batch data
+ * Parameters:
+ *     probs: 3-D vector where each element is a 2-D vector that can be used
+ *                by ctc_beam_search_decoder().
+ *     alphabet: The alphabet.
+ *     beam_size: The width of beam search.
+ *     num_processes: Number of threads for beam search.
+ *     cutoff_prob: Cutoff probability for pruning.
+ *     cutoff_top_n: Cutoff number for pruning.
+ *     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.
+ * Return:
+ *     A 2-D vector where each element is a vector of beam search decoding
+ *     result for one audio sample.
+*/
+std::vector<std::vector<Output>>
+ctc_beam_search_decoder_batch(
+    const double* probs,
+    int batch_size,
+    int time_dim,
+    int class_dim,
+    const int* seq_lengths,
+    int seq_lengths_size,
+    const Alphabet &alphabet,
+    size_t beam_size,
+    size_t num_processes,
+    double cutoff_prob,
+    size_t cutoff_top_n,
+    Scorer *ext_scorer);
+
 #endif  // CTC_BEAM_SEARCH_DECODER_H_