add beam search decoder using multiprocesses

decoder.py

@@ -2,11 +2,12 @@
     CTC-like decoder utilitis.
 """
 
+import os
 from itertools import groupby
 import numpy as np
 import copy
 import kenlm
-import os
+import multiprocessing
 
 
 def ctc_best_path_decode(probs_seq, vocabulary):
@@ -187,3 +188,54 @@ def ctc_beam_search_decoder(probs_seq,
     ## output top beam_size decoding results
     beam_result = sorted(beam_result, key=lambda asd: asd[0], reverse=True)
     return beam_result
+
+
+def ctc_beam_search_decoder_nproc(probs_split,
+                                  beam_size,
+                                  vocabulary,
+                                  ext_scoring_func=None,
+                                  blank_id=0,
+                                  num_processes=None):
+    '''
+    Beam search decoder using multiple processes.
+
+    :param probs_seq: 3-D list with length num_time_steps, each element
+                      is a 2-D list of  probabilities can be used by
+                      ctc_beam_search_decoder.
+
+    :type probs_seq: 3-D list
+    :param beam_size: Width for beam search.
+    :type beam_size: int
+    :param vocabulary: Vocabulary list.
+    :type vocabulary: list
+    :param ext_scoring_func: External defined scoring function for
+                            partially decoded sentence, e.g. word count
+                            and language model.
+    :type external_scoring_function: function
+    :param blank_id: id of blank, default 0.
+    :type blank_id: int
+    :param num_processes: Number of processes, default None, equal to the
+                 number of CPUs.
+    :type num_processes: int
+    :return: Decoding log probability and result string.
+    :rtype: list
+
+    '''
+
+    if num_processes is None:
+        num_processes = multiprocessing.cpu_count()
+    if not num_processes > 0:
+        raise ValueError("Number of processes must be positive!")
+
+    pool = multiprocessing.Pool(processes=num_processes)
+    results = []
+    for i, probs_list in enumerate(probs_split):
+        args = (probs_list, beam_size, vocabulary, ext_scoring_func, blank_id)
+        results.append(pool.apply_async(ctc_beam_search_decoder, args))
+
+    pool.close()
+    pool.join()
+    beam_search_results = []
+    for result in results:
+        beam_search_results.append(result.get())
+    return beam_search_results

infer.py

@@ -9,6 +9,7 @@ import gzip
 from audio_data_utils import DataGenerator
 from model import deep_speech2
 from decoder import *
+from error_rate import wer
 
 parser = argparse.ArgumentParser(
     description='Simplified version of DeepSpeech2 inference.')
@@ -59,9 +60,9 @@ parser.add_argument(
     help="Vocabulary filepath. (default: %(default)s)")
 parser.add_argument(
     "--decode_method",
-    default='beam_search',
+    default='beam_search_nproc',
     type=str,
-    help="Method for ctc decoding, best_path or beam_search. (default: %(default)s)"
+    help="Method for ctc decoding, best_path, beam_search or beam_search_nproc. (default: %(default)s)"
 )
 parser.add_argument(
     "--beam_size",
@@ -151,6 +152,7 @@ def infer():
 
     ## decode and print
     # best path decode
+    wer_sum, wer_counter = 0, 0
     if args.decode_method == "best_path":
         for i, probs in enumerate(probs_split):
             target_transcription = ''.join(
@@ -159,12 +161,17 @@ def infer():
                 probs_seq=probs, vocabulary=vocab_list)
             print("\nTarget Transcription: %s\nOutput Transcription: %s" %
                   (target_transcription, best_path_transcription))
+            wer_cur = wer(target_transcription, best_path_transcription)
+            wer_sum += wer_cur
+            wer_counter += 1
+            print("cur wer = %f, average wer = %f" %
+                  (wer_cur, wer_sum / wer_counter))
     # beam search decode
     elif args.decode_method == "beam_search":
+        ext_scorer = Scorer(args.alpha, args.beta, args.language_model_path)
         for i, probs in enumerate(probs_split):
             target_transcription = ''.join(
                 [vocab_list[index] for index in infer_data[i][1]])
-            ext_scorer = Scorer(args.alpha, args.beta, args.language_model_path)
             beam_search_result = ctc_beam_search_decoder(
                 probs_seq=probs,
                 vocabulary=vocab_list,
@@ -172,10 +179,40 @@ def infer():
                 ext_scoring_func=ext_scorer.evaluate,
                 blank_id=len(vocab_list))
             print("\nTarget Transcription:\t%s" % target_transcription)
+
+            for index in range(args.num_results_per_sample):
+                result = beam_search_result[index]
+                #output: index, log prob, beam result
+                print("Beam %d: %f \t%s" % (index, result[0], result[1]))
+            wer_cur = wer(target_transcription, beam_search_result[0][1])
+            wer_sum += wer_cur
+            wer_counter += 1
+            print("cur wer = %f , average wer = %f" %
+                  (wer_cur, wer_sum / wer_counter))
+    # beam search in multiple processes
+    elif args.decode_method == "beam_search_nproc":
+        ext_scorer = Scorer(args.alpha, args.beta, args.language_model_path)
+        beam_search_nproc_results = ctc_beam_search_decoder_nproc(
+            probs_split=probs_split,
+            vocabulary=vocab_list,
+            beam_size=args.beam_size,
+            #ext_scoring_func=ext_scorer.evaluate,
+            ext_scoring_func=None,
+            blank_id=len(vocab_list))
+        for i, beam_search_result in enumerate(beam_search_nproc_results):
+            target_transcription = ''.join(
+                [vocab_list[index] for index in infer_data[i][1]])
+            print("\nTarget Transcription:\t%s" % target_transcription)
+
             for index in range(args.num_results_per_sample):
                 result = beam_search_result[index]
                 #output: index, log prob, beam result
                 print("Beam %d: %f \t%s" % (index, result[0], result[1]))
+            wer_cur = wer(target_transcription, beam_search_result[0][1])
+            wer_sum += wer_cur
+            wer_counter += 1
+            print("cur wer = %f , average wer = %f" %
+                  (wer_cur, wer_sum / wer_counter))
     else:
         raise ValueError("Decoding method [%s] is not supported." % method)