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@ -11,6 +11,7 @@
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# limitations under the License.
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import copy
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from collections import defaultdict
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from collections import defaultdict
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import paddle
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import paddle
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@ -26,7 +27,7 @@ class CTCPrefixBeamSearch:
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"""Implement the ctc prefix beam search
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"""Implement the ctc prefix beam search
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Args:
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Args:
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config (yacs.config.CfgNode): _description_
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config (yacs.config.CfgNode): the ctc prefix beam search configuration
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"""
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"""
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self.config = config
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self.config = config
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self.reset()
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self.reset()
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@ -54,14 +55,23 @@ class CTCPrefixBeamSearch:
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assert len(ctc_probs.shape) == 2
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assert len(ctc_probs.shape) == 2
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# cur_hyps: (prefix, (blank_ending_score, none_blank_ending_score))
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# cur_hyps: (prefix, (blank_ending_score, none_blank_ending_score))
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# blank_ending_score and none_blank_ending_score in ln domain
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# 0. blank_ending_score,
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# 1. none_blank_ending_score,
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# 2. viterbi_blank ending,
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# 3. viterbi_non_blank,
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# 4. current_token_prob,
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# 5. times_viterbi_blank,
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# 6. times_titerbi_non_blank
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if self.cur_hyps is None:
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if self.cur_hyps is None:
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self.cur_hyps = [(tuple(), (0.0, -float('inf')))]
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self.cur_hyps = [(tuple(), (0.0, -float('inf'), 0.0, 0.0,
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-float('inf'), [], []))]
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# self.cur_hyps = [(tuple(), (0.0, -float('inf')))]
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# 2. CTC beam search step by step
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# 2. CTC beam search step by step
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for t in range(0, maxlen):
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for t in range(0, maxlen):
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logp = ctc_probs[t] # (vocab_size,)
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logp = ctc_probs[t] # (vocab_size,)
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# key: prefix, value (pb, pnb), default value(-inf, -inf)
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# next_hyps = defaultdict(lambda: (-float('inf'), -float('inf')))
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next_hyps = defaultdict(lambda: (-float('inf'), -float('inf')))
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next_hyps = defaultdict(
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lambda: (-float('inf'), -float('inf'), -float('inf'), -float('inf'), -float('inf'), [], []))
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# 2.1 First beam prune: select topk best
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# 2.1 First beam prune: select topk best
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# do token passing process
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# do token passing process
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@ -69,36 +79,83 @@ class CTCPrefixBeamSearch:
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for s in top_k_index:
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for s in top_k_index:
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s = s.item()
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s = s.item()
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ps = logp[s].item()
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ps = logp[s].item()
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for prefix, (pb, pnb) in self.cur_hyps:
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for prefix, (pb, pnb, v_b_s, v_nb_s, cur_token_prob, times_s,
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times_ns) in self.cur_hyps:
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last = prefix[-1] if len(prefix) > 0 else None
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last = prefix[-1] if len(prefix) > 0 else None
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if s == blank_id: # blank
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if s == blank_id: # blank
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n_pb, n_pnb = next_hyps[prefix]
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n_pb, n_pnb, n_v_s, n_v_ns, n_cur_token_prob, n_times_s, n_times_ns = next_hyps[
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prefix]
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n_pb = log_add([n_pb, pb + ps, pnb + ps])
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n_pb = log_add([n_pb, pb + ps, pnb + ps])
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next_hyps[prefix] = (n_pb, n_pnb)
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pre_times = times_s if v_b_s > v_nb_s else times_ns
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n_times_s = copy.deepcopy(pre_times)
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viterbi_score = v_b_s if v_b_s > v_nb_s else v_nb_s
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n_v_s = viterbi_score + ps
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next_hyps[prefix] = (n_pb, n_pnb, n_v_s, n_v_ns,
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n_cur_token_prob, n_times_s,
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n_times_ns)
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elif s == last:
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elif s == last:
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# Update *ss -> *s;
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# Update *ss -> *s;
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n_pb, n_pnb = next_hyps[prefix]
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# case1: *a + a => *a
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n_pb, n_pnb, n_v_s, n_v_ns, n_cur_token_prob, n_times_s, n_times_ns = next_hyps[
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prefix]
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n_pnb = log_add([n_pnb, pnb + ps])
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n_pnb = log_add([n_pnb, pnb + ps])
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next_hyps[prefix] = (n_pb, n_pnb)
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if n_v_ns < v_nb_s + ps:
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n_v_ns = v_nb_s + ps
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if n_cur_token_prob < ps:
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n_cur_token_prob = ps
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n_times_ns = copy.deepcopy(times_ns)
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n_times_ns[
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-1] = self.abs_time_step # 注意,这里要重新使用绝对时间
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next_hyps[prefix] = (n_pb, n_pnb, n_v_s, n_v_ns,
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n_cur_token_prob, n_times_s,
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n_times_ns)
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# Update *s-s -> *ss, - is for blank
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# Update *s-s -> *ss, - is for blank
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# Case 2: *aε + a => *aa
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n_prefix = prefix + (s, )
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n_prefix = prefix + (s, )
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n_pb, n_pnb = next_hyps[n_prefix]
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n_pb, n_pnb, n_v_s, n_v_ns, n_cur_token_prob, n_times_s, n_times_ns = next_hyps[
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n_prefix]
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if n_v_ns < v_b_s + ps:
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n_v_ns = v_b_s + ps
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n_cur_token_prob = ps
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n_times_ns = copy.deepcopy(times_s)
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n_times_ns.append(self.abs_time_step)
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n_pnb = log_add([n_pnb, pb + ps])
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n_pnb = log_add([n_pnb, pb + ps])
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next_hyps[n_prefix] = (n_pb, n_pnb)
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next_hyps[n_prefix] = (n_pb, n_pnb, n_v_s, n_v_ns,
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n_cur_token_prob, n_times_s,
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n_times_ns)
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else:
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else:
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# Case 3: *a + b => *ab, *aε + b => *ab
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n_prefix = prefix + (s, )
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n_prefix = prefix + (s, )
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n_pb, n_pnb = next_hyps[n_prefix]
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n_pb, n_pnb, n_v_s, n_v_ns, n_cur_token_prob, n_times_s, n_times_ns = next_hyps[
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n_prefix]
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viterbi_score = v_b_s if v_b_s > v_nb_s else v_nb_s
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pre_times = times_s if v_b_s > v_nb_s else times_ns
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if n_v_ns < viterbi_score + ps:
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n_v_ns = viterbi_score + ps
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n_cur_token_prob = ps
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n_times_ns = copy.deepcopy(pre_times)
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n_times_ns.append(self.abs_time_step)
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n_pnb = log_add([n_pnb, pb + ps, pnb + ps])
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n_pnb = log_add([n_pnb, pb + ps, pnb + ps])
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next_hyps[n_prefix] = (n_pb, n_pnb)
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next_hyps[n_prefix] = (n_pb, n_pnb, n_v_s, n_v_ns,
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n_cur_token_prob, n_times_s,
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n_times_ns)
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# 2.2 Second beam prune
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# 2.2 Second beam prune
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next_hyps = sorted(
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next_hyps = sorted(
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next_hyps.items(),
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next_hyps.items(),
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key=lambda x: log_add(list(x[1])),
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key=lambda x: log_add([x[1][0], x[1][1]]),
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reverse=True)
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reverse=True)
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self.cur_hyps = next_hyps[:beam_size]
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self.cur_hyps = next_hyps[:beam_size]
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self.hyps = [(y[0], log_add([y[1][0], y[1][1]])) for y in self.cur_hyps]
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# 2.3 update the absolute time step
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self.abs_time_step += 1
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self.hyps = [(y[0], log_add([y[1][0], y[1][1]]), y[1][2], y[1][3],
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y[1][4], y[1][5], y[1][6]) for y in self.cur_hyps]
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logger.info("ctc prefix search success")
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logger.info("ctc prefix search success")
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return self.hyps
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return self.hyps
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@ -123,6 +180,7 @@ class CTCPrefixBeamSearch:
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"""
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"""
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self.cur_hyps = None
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self.cur_hyps = None
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self.hyps = None
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self.hyps = None
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self.abs_time_step = 0
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def finalize_search(self):
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def finalize_search(self):
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"""do nothing in ctc_prefix_beam_search
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"""do nothing in ctc_prefix_beam_search
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