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3
README.md
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@ -220,8 +220,7 @@ and [Pruned stateless RNN-T: Conformer encoder + Embedding decoder + k2 pruned R
### Aidatatang_200zh ### Aidatatang_200zh
We provide one model for this recipe: [Pruned stateless RNN-T: Conformer encoder + Embedding decoder + k2 pruned RNN-T loss][Aidatatang_200zh We provide one model for this recipe: [Pruned stateless RNN-T: Conformer encoder + Embedding decoder + k2 pruned RNN-T loss][Aidatatang_200zh_pruned_transducer_stateless2].
_pruned_transducer_stateless2].
#### Pruned stateless RNN-T: Conformer encoder + Embedding decoder + k2 pruned RNN-T loss #### Pruned stateless RNN-T: Conformer encoder + Embedding decoder + k2 pruned RNN-T loss

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egs/aidatatang_200zh/ASR/README.md
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@ -1,5 +1,4 @@
Note: This recipe is trained with the codes from this PR https://github.com/k2-fsa/icefall/pull/355 Note: This recipe is trained with the codes from this PR https://github.com/k2-fsa/icefall/pull/375
And the SpecAugment codes from this PR https://github.com/lhotse-speech/lhotse/pull/604.
# Pre-trained Transducer-Stateless2 models for the Aidatatang_200zh dataset with icefall. # Pre-trained Transducer-Stateless2 models for the Aidatatang_200zh dataset with icefall.
The model was trained on full [Aidatatang_200zh](https://www.openslr.org/62) with the scripts in [icefall](https://github.com/k2-fsa/icefall) based on the latest version k2. The model was trained on full [Aidatatang_200zh](https://www.openslr.org/62) with the scripts in [icefall](https://github.com/k2-fsa/icefall) based on the latest version k2.
## Training procedure ## Training procedure
@ -35,5 +34,5 @@ The WERs are
| | dev | test | comment | | | dev | test | comment |
|------------------------------------|------------|------------|------------------------------------------| |------------------------------------|------------|------------|------------------------------------------|
| greedy search | 5.53 | 6.59 | --epoch 29, --avg 19, --max-duration 100 | | greedy search | 5.53 | 6.59 | --epoch 29, --avg 19, --max-duration 100 |
| modified beam search (beam size 4) | 5.28 | 6.32 | --epoch 29, --avg 19, --max-duration 100 | | modified beam search (beam size 4) | 5.27 | 6.33 | --epoch 29, --avg 19, --max-duration 100 |
| fast beam search (set as default) | 5.29 | 6.33 | --epoch 29, --avg 19, --max-duration 1500| | fast beam search (set as default) | 5.30 | 6.34 | --epoch 29, --avg 19, --max-duration 1500|

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egs/aidatatang_200zh/ASR/RESULTS.md
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@ -4,7 +4,7 @@
#### 2022-05-16 #### 2022-05-16
Using the codes from this PR https://github.com/k2-fsa/icefall/pull/355. Using the codes from this PR https://github.com/k2-fsa/icefall/pull/375.
The WERs are The WERs are

6
egs/aidatatang_200zh/ASR/local/compute_fbank_aidatatang_200zh.py
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@ -17,7 +17,7 @@
""" """
This file computes fbank features of the aishell dataset. This file computes fbank features of the aidatatang_200zh dataset.
It looks for manifests in the directory data/manifests. It looks for manifests in the directory data/manifests.
The generated fbank features are saved in data/fbank. The generated fbank features are saved in data/fbank.
@ -42,7 +42,7 @@ torch.set_num_threads(1)
torch.set_num_interop_threads(1) torch.set_num_interop_threads(1)
def compute_fbank_aishell(num_mel_bins: int = 80): def compute_fbank_aidatatang_200zh(num_mel_bins: int = 80):
src_dir = Path("data/manifests/aidatatang_200zh") src_dir = Path("data/manifests/aidatatang_200zh")
output_dir = Path("data/fbank") output_dir = Path("data/fbank")
num_jobs = min(15, os.cpu_count()) num_jobs = min(15, os.cpu_count())
@ -106,4 +106,4 @@ if __name__ == "__main__":
logging.basicConfig(format=formatter, level=logging.INFO) logging.basicConfig(format=formatter, level=logging.INFO)
args = get_args() args = get_args()
compute_fbank_aishell(num_mel_bins=args.num_mel_bins) compute_fbank_aidatatang_200zh(num_mel_bins=args.num_mel_bins)

4
egs/aidatatang_200zh/ASR/pruned_transducer_stateless2/asr_datamodule.py
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@ -354,8 +354,6 @@ class Aidatatang_200zhAsrDataModule:
valid_sampler = DynamicBucketingSampler( valid_sampler = DynamicBucketingSampler(
cuts_valid, cuts_valid,
max_duration=self.args.max_duration, max_duration=self.args.max_duration,
rank=0,
world_size=1,
shuffle=False, shuffle=False,
) )
logging.info("About to create dev dataloader") logging.info("About to create dev dataloader")
@ -386,8 +384,6 @@ class Aidatatang_200zhAsrDataModule:
sampler = DynamicBucketingSampler( sampler = DynamicBucketingSampler(
cuts, cuts,
max_duration=self.args.max_duration, max_duration=self.args.max_duration,
rank=0,
world_size=1,
shuffle=False, shuffle=False,
) )
from lhotse.dataset.iterable_dataset import IterableDatasetWrapper from lhotse.dataset.iterable_dataset import IterableDatasetWrapper

955
egs/aidatatang_200zh/ASR/pruned_transducer_stateless2/beam_search.py
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@ -1,955 +0,0 @@
# Copyright 2021 Xiaomi Corp. (authors: Fangjun Kuang)
#
# See ../../../../LICENSE for clarification regarding multiple authors
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import warnings
from dataclasses import dataclass
from typing import Dict, List, Optional
import k2
import torch
from model import Transducer
from icefall.decode import Nbest, one_best_decoding
from icefall.utils import get_texts
def fast_beam_search_one_best(
model: Transducer,
decoding_graph: k2.Fsa,
encoder_out: torch.Tensor,
encoder_out_lens: torch.Tensor,
beam: float,
max_states: int,
max_contexts: int,
) -> List[List[int]]:
"""It limits the maximum number of symbols per frame to 1.
A lattice is first obtained using modified beam search, and then
the shortest path within the lattice is used as the final output.
Args:
model:
An instance of `Transducer`.
decoding_graph:
Decoding graph used for decoding, may be a TrivialGraph or a HLG.
encoder_out:
A tensor of shape (N, T, C) from the encoder.
encoder_out_lens:
A tensor of shape (N,) containing the number of frames in `encoder_out`
before padding.
beam:
Beam value, similar to the beam used in Kaldi..
max_states:
Max states per stream per frame.
max_contexts:
Max contexts pre stream per frame.
Returns:
Return the decoded result.
"""
lattice = fast_beam_search(
model=model,
decoding_graph=decoding_graph,
encoder_out=encoder_out,
encoder_out_lens=encoder_out_lens,
beam=beam,
max_states=max_states,
max_contexts=max_contexts,
)
best_path = one_best_decoding(lattice)
hyps = get_texts(best_path)
return hyps
def fast_beam_search_nbest_oracle(
model: Transducer,
decoding_graph: k2.Fsa,
encoder_out: torch.Tensor,
encoder_out_lens: torch.Tensor,
beam: float,
max_states: int,
max_contexts: int,
num_paths: int,
ref_texts: List[List[int]],
use_double_scores: bool = True,
nbest_scale: float = 0.5,
) -> List[List[int]]:
"""It limits the maximum number of symbols per frame to 1.
A lattice is first obtained using modified beam search, and then
we select `num_paths` linear paths from the lattice. The path
that has the minimum edit distance with the given reference transcript
is used as the output.
This is the best result we can achieve for any nbest based rescoring
methods.
Args:
model:
An instance of `Transducer`.
decoding_graph:
Decoding graph used for decoding, may be a TrivialGraph or a HLG.
encoder_out:
A tensor of shape (N, T, C) from the encoder.
encoder_out_lens:
A tensor of shape (N,) containing the number of frames in `encoder_out`
before padding.
beam:
Beam value, similar to the beam used in Kaldi..
max_states:
Max states per stream per frame.
max_contexts:
Max contexts pre stream per frame.
num_paths:
Number of paths to extract from the decoded lattice.
ref_texts:
A list-of-list of integers containing the reference transcripts.
If the decoding_graph is a trivial_graph, the integer ID is the
BPE token ID.
use_double_scores:
True to use double precision for computation. False to use
single precision.
nbest_scale:
It's the scale applied to the lattice.scores. A smaller value
yields more unique paths.
Returns:
Return the decoded result.
"""
lattice = fast_beam_search(
model=model,
decoding_graph=decoding_graph,
encoder_out=encoder_out,
encoder_out_lens=encoder_out_lens,
beam=beam,
max_states=max_states,
max_contexts=max_contexts,
)
nbest = Nbest.from_lattice(
lattice=lattice,
num_paths=num_paths,
use_double_scores=use_double_scores,
nbest_scale=nbest_scale,
)
hyps = nbest.build_levenshtein_graphs()
refs = k2.levenshtein_graph(ref_texts, device=hyps.device)
levenshtein_alignment = k2.levenshtein_alignment(
refs=refs,
hyps=hyps,
hyp_to_ref_map=nbest.shape.row_ids(1),
sorted_match_ref=True,
)
tot_scores = levenshtein_alignment.get_tot_scores(
use_double_scores=False, log_semiring=False
)
ragged_tot_scores = k2.RaggedTensor(nbest.shape, tot_scores)
max_indexes = ragged_tot_scores.argmax()
best_path = k2.index_fsa(nbest.fsa, max_indexes)
hyps = get_texts(best_path)
return hyps
def fast_beam_search(
model: Transducer,
decoding_graph: k2.Fsa,
encoder_out: torch.Tensor,
encoder_out_lens: torch.Tensor,
beam: float,
max_states: int,
max_contexts: int,
) -> k2.Fsa:
"""It limits the maximum number of symbols per frame to 1.
Args:
model:
An instance of `Transducer`.
decoding_graph:
Decoding graph used for decoding, may be a TrivialGraph or a HLG.
encoder_out:
A tensor of shape (N, T, C) from the encoder.
encoder_out_lens:
A tensor of shape (N,) containing the number of frames in `encoder_out`
before padding.
beam:
Beam value, similar to the beam used in Kaldi..
max_states:
Max states per stream per frame.
max_contexts:
Max contexts pre stream per frame.
Returns:
Return an FsaVec with axes [utt][state][arc] containing the decoded
lattice. Note: When the input graph is a TrivialGraph, the returned
lattice is actually an acceptor.
"""
assert encoder_out.ndim == 3
context_size = model.decoder.context_size
vocab_size = model.decoder.vocab_size
B, T, C = encoder_out.shape
config = k2.RnntDecodingConfig(
vocab_size=vocab_size,
decoder_history_len=context_size,
beam=beam,
max_contexts=max_contexts,
max_states=max_states,
)
individual_streams = []
for i in range(B):
individual_streams.append(k2.RnntDecodingStream(decoding_graph))
decoding_streams = k2.RnntDecodingStreams(individual_streams, config)
encoder_out = model.joiner.encoder_proj(encoder_out)
for t in range(T):
# shape is a RaggedShape of shape (B, context)
# contexts is a Tensor of shape (shape.NumElements(), context_size)
shape, contexts = decoding_streams.get_contexts()
# `nn.Embedding()` in torch below v1.7.1 supports only torch.int64
contexts = contexts.to(torch.int64)
# decoder_out is of shape (shape.NumElements(), 1, decoder_out_dim)
decoder_out = model.decoder(contexts, need_pad=False)
decoder_out = model.joiner.decoder_proj(decoder_out)
# current_encoder_out is of shape
# (shape.NumElements(), 1, joiner_dim)
# fmt: off
current_encoder_out = torch.index_select(
encoder_out[:, t:t + 1, :], 0, shape.row_ids(1).to(torch.int64)
)
# fmt: on
logits = model.joiner(
current_encoder_out.unsqueeze(2),
decoder_out.unsqueeze(1),
project_input=False,
)
logits = logits.squeeze(1).squeeze(1)
log_probs = logits.log_softmax(dim=-1)
decoding_streams.advance(log_probs)
decoding_streams.terminate_and_flush_to_streams()
lattice = decoding_streams.format_output(encoder_out_lens.tolist())
return lattice
def greedy_search(
model: Transducer, encoder_out: torch.Tensor, max_sym_per_frame: int
) -> List[int]:
"""Greedy search for a single utterance.
Args:
model:
An instance of `Transducer`.
encoder_out:
A tensor of shape (N, T, C) from the encoder. Support only N==1 for now.
max_sym_per_frame:
Maximum number of symbols per frame. If it is set to 0, the WER
would be 100%.
Returns:
Return the decoded result.
"""
assert encoder_out.ndim == 3
# support only batch_size == 1 for now
assert encoder_out.size(0) == 1, encoder_out.size(0)
blank_id = model.decoder.blank_id
context_size = model.decoder.context_size
unk_id = getattr(model, "unk_id", blank_id)
device = next(model.parameters()).device
decoder_input = torch.tensor(
[blank_id] * context_size, device=device, dtype=torch.int64
).reshape(1, context_size)
decoder_out = model.decoder(decoder_input, need_pad=False)
decoder_out = model.joiner.decoder_proj(decoder_out)
encoder_out = model.joiner.encoder_proj(encoder_out)
T = encoder_out.size(1)
t = 0
hyp = [blank_id] * context_size
# Maximum symbols per utterance.
max_sym_per_utt = 1000
# symbols per frame
sym_per_frame = 0
# symbols per utterance decoded so far
sym_per_utt = 0
while t < T and sym_per_utt < max_sym_per_utt:
if sym_per_frame >= max_sym_per_frame:
sym_per_frame = 0
t += 1
continue
# fmt: off
current_encoder_out = encoder_out[:, t:t+1, :].unsqueeze(2)
# fmt: on
logits = model.joiner(
current_encoder_out, decoder_out.unsqueeze(1), project_input=False
)
# logits is (1, 1, 1, vocab_size)
y = logits.argmax().item()
if y not in (blank_id, unk_id):
hyp.append(y)
decoder_input = torch.tensor(
[hyp[-context_size:]], device=device
).reshape(1, context_size)
decoder_out = model.decoder(decoder_input, need_pad=False)
decoder_out = model.joiner.decoder_proj(decoder_out)
sym_per_utt += 1
sym_per_frame += 1
else:
sym_per_frame = 0
t += 1
hyp = hyp[context_size:] # remove blanks
return hyp
def greedy_search_batch(
model: Transducer,
encoder_out: torch.Tensor,
encoder_out_lens: torch.Tensor,
) -> List[List[int]]:
"""Greedy search in batch mode. It hardcodes --max-sym-per-frame=1.
Args:
model:
The transducer model.
encoder_out:
Output from the encoder. Its shape is (N, T, C), where N >= 1.
encoder_out_lens:
A 1-D tensor of shape (N,), containing number of valid frames in
encoder_out before padding.
Returns:
Return a list-of-list of token IDs containing the decoded results.
len(ans) equals to encoder_out.size(0).
"""
assert encoder_out.ndim == 3
assert encoder_out.size(0) >= 1, encoder_out.size(0)
packed_encoder_out = torch.nn.utils.rnn.pack_padded_sequence(
input=encoder_out,
lengths=encoder_out_lens.cpu(),
batch_first=True,
enforce_sorted=False,
)
device = next(model.parameters()).device
blank_id = model.decoder.blank_id
unk_id = getattr(model, "unk_id", blank_id)
context_size = model.decoder.context_size
batch_size_list = packed_encoder_out.batch_sizes.tolist()
N = encoder_out.size(0)
assert torch.all(encoder_out_lens > 0), encoder_out_lens
assert N == batch_size_list[0], (N, batch_size_list)
hyps = [[blank_id] * context_size for _ in range(N)]
decoder_input = torch.tensor(
hyps,
device=device,
dtype=torch.int64,
) # (N, context_size)
decoder_out = model.decoder(decoder_input, need_pad=False)
decoder_out = model.joiner.decoder_proj(decoder_out)
# decoder_out: (N, 1, decoder_out_dim)
encoder_out = model.joiner.encoder_proj(packed_encoder_out.data)
offset = 0
for batch_size in batch_size_list:
start = offset
end = offset + batch_size
current_encoder_out = encoder_out.data[start:end]
current_encoder_out = current_encoder_out.unsqueeze(1).unsqueeze(1)
# current_encoder_out's shape: (batch_size, 1, 1, encoder_out_dim)
offset = end
decoder_out = decoder_out[:batch_size]
logits = model.joiner(
current_encoder_out, decoder_out.unsqueeze(1), project_input=False
)
# logits'shape (batch_size, 1, 1, vocab_size)
logits = logits.squeeze(1).squeeze(1) # (batch_size, vocab_size)
assert logits.ndim == 2, logits.shape
y = logits.argmax(dim=1).tolist()
emitted = False
for i, v in enumerate(y):
if v not in (blank_id, unk_id):
hyps[i].append(v)
emitted = True
if emitted:
# update decoder output
decoder_input = [h[-context_size:] for h in hyps[:batch_size]]
decoder_input = torch.tensor(
decoder_input,
device=device,
dtype=torch.int64,
)
decoder_out = model.decoder(decoder_input, need_pad=False)
decoder_out = model.joiner.decoder_proj(decoder_out)
sorted_ans = [h[context_size:] for h in hyps]
ans = []
unsorted_indices = packed_encoder_out.unsorted_indices.tolist()
for i in range(N):
ans.append(sorted_ans[unsorted_indices[i]])
return ans
@dataclass
class Hypothesis:
# The predicted tokens so far.
# Newly predicted tokens are appended to `ys`.
ys: List[int]
# The log prob of ys.
# It contains only one entry.
log_prob: torch.Tensor
@property
def key(self) -> str:
"""Return a string representation of self.ys"""
return "_".join(map(str, self.ys))
class HypothesisList(object):
def __init__(self, data: Optional[Dict[str, Hypothesis]] = None) -> None:
"""
Args:
data:
A dict of Hypotheses. Its key is its `value.key`.
"""
if data is None:
self._data = {}
else:
self._data = data
@property
def data(self) -> Dict[str, Hypothesis]:
return self._data
def add(self, hyp: Hypothesis) -> None:
"""Add a Hypothesis to `self`.
If `hyp` already exists in `self`, its probability is updated using
`log-sum-exp` with the existed one.
Args:
hyp:
The hypothesis to be added.
"""
key = hyp.key
if key in self:
old_hyp = self._data[key] # shallow copy
torch.logaddexp(
old_hyp.log_prob, hyp.log_prob, out=old_hyp.log_prob
)
else:
self._data[key] = hyp
def get_most_probable(self, length_norm: bool = False) -> Hypothesis:
"""Get the most probable hypothesis, i.e., the one with
the largest `log_prob`.
Args:
length_norm:
If True, the `log_prob` of a hypothesis is normalized by the
number of tokens in it.
Returns:
Return the hypothesis that has the largest `log_prob`.
"""
if length_norm:
return max(
self._data.values(), key=lambda hyp: hyp.log_prob / len(hyp.ys)
)
else:
return max(self._data.values(), key=lambda hyp: hyp.log_prob)
def remove(self, hyp: Hypothesis) -> None:
"""Remove a given hypothesis.
Caution:
`self` is modified **in-place**.
Args:
hyp:
The hypothesis to be removed from `self`.
Note: It must be contained in `self`. Otherwise,
an exception is raised.
"""
key = hyp.key
assert key in self, f"{key} does not exist"
del self._data[key]
def filter(self, threshold: torch.Tensor) -> "HypothesisList":
"""Remove all Hypotheses whose log_prob is less than threshold.
Caution:
`self` is not modified. Instead, a new HypothesisList is returned.
Returns:
Return a new HypothesisList containing all hypotheses from `self`
with `log_prob` being greater than the given `threshold`.
"""
ans = HypothesisList()
for _, hyp in self._data.items():
if hyp.log_prob > threshold:
ans.add(hyp) # shallow copy
return ans
def topk(self, k: int) -> "HypothesisList":
"""Return the top-k hypothesis."""
hyps = list(self._data.items())
hyps = sorted(hyps, key=lambda h: h[1].log_prob, reverse=True)[:k]
ans = HypothesisList(dict(hyps))
return ans
def __contains__(self, key: str):
return key in self._data
def __iter__(self):
return iter(self._data.values())
def __len__(self) -> int:
return len(self._data)
def __str__(self) -> str:
s = []
for key in self:
s.append(key)
return ", ".join(s)
def _get_hyps_shape(hyps: List[HypothesisList]) -> k2.RaggedShape:
"""Return a ragged shape with axes [utt][num_hyps].
Args:
hyps:
len(hyps) == batch_size. It contains the current hypothesis for
each utterance in the batch.
Returns:
Return a ragged shape with 2 axes [utt][num_hyps]. Note that
the shape is on CPU.
"""
num_hyps = [len(h) for h in hyps]
# torch.cumsum() is inclusive sum, so we put a 0 at the beginning
# to get exclusive sum later.
num_hyps.insert(0, 0)
num_hyps = torch.tensor(num_hyps)
row_splits = torch.cumsum(num_hyps, dim=0, dtype=torch.int32)
ans = k2.ragged.create_ragged_shape2(
row_splits=row_splits, cached_tot_size=row_splits[-1].item()
)
return ans
def modified_beam_search(
model: Transducer,
encoder_out: torch.Tensor,
encoder_out_lens: torch.Tensor,
beam: int = 4,
) -> List[List[int]]:
"""Beam search in batch mode with --max-sym-per-frame=1 being hardcoded.
Args:
model:
The transducer model.
encoder_out:
Output from the encoder. Its shape is (N, T, C).
encoder_out_lens:
A 1-D tensor of shape (N,), containing number of valid frames in
encoder_out before padding.
beam:
Number of active paths during the beam search.
Returns:
Return a list-of-list of token IDs. ans[i] is the decoding results
for the i-th utterance.
"""
assert encoder_out.ndim == 3, encoder_out.shape
assert encoder_out.size(0) >= 1, encoder_out.size(0)
packed_encoder_out = torch.nn.utils.rnn.pack_padded_sequence(
input=encoder_out,
lengths=encoder_out_lens.cpu(),
batch_first=True,
enforce_sorted=False,
)
blank_id = model.decoder.blank_id
unk_id = getattr(model, "unk_id", blank_id)
context_size = model.decoder.context_size
device = next(model.parameters()).device
batch_size_list = packed_encoder_out.batch_sizes.tolist()
N = encoder_out.size(0)
assert torch.all(encoder_out_lens > 0), encoder_out_lens
assert N == batch_size_list[0], (N, batch_size_list)
B = [HypothesisList() for _ in range(N)]
for i in range(N):
B[i].add(
Hypothesis(
ys=[blank_id] * context_size,
log_prob=torch.zeros(1, dtype=torch.float32, device=device),
)
)
encoder_out = model.joiner.encoder_proj(packed_encoder_out.data)
offset = 0
finalized_B = []
for batch_size in batch_size_list:
start = offset
end = offset + batch_size
current_encoder_out = encoder_out.data[start:end]
current_encoder_out = current_encoder_out.unsqueeze(1).unsqueeze(1)
# current_encoder_out's shape is (batch_size, 1, 1, encoder_out_dim)
offset = end
finalized_B = B[batch_size:] + finalized_B
B = B[:batch_size]
hyps_shape = _get_hyps_shape(B).to(device)
A = [list(b) for b in B]
B = [HypothesisList() for _ in range(batch_size)]
ys_log_probs = torch.cat(
[hyp.log_prob.reshape(1, 1) for hyps in A for hyp in hyps]
) # (num_hyps, 1)
decoder_input = torch.tensor(
[hyp.ys[-context_size:] for hyps in A for hyp in hyps],
device=device,
dtype=torch.int64,
) # (num_hyps, context_size)
decoder_out = model.decoder(decoder_input, need_pad=False).unsqueeze(1)
decoder_out = model.joiner.decoder_proj(decoder_out)
# decoder_out is of shape (num_hyps, 1, 1, joiner_dim)
# Note: For torch 1.7.1 and below, it requires a torch.int64 tensor
# as index, so we use `to(torch.int64)` below.
current_encoder_out = torch.index_select(
current_encoder_out,
dim=0,
index=hyps_shape.row_ids(1).to(torch.int64),
) # (num_hyps, 1, 1, encoder_out_dim)
logits = model.joiner(
current_encoder_out,
decoder_out,
project_input=False,
) # (num_hyps, 1, 1, vocab_size)
logits = logits.squeeze(1).squeeze(1) # (num_hyps, vocab_size)
log_probs = logits.log_softmax(dim=-1) # (num_hyps, vocab_size)
log_probs.add_(ys_log_probs)
vocab_size = log_probs.size(-1)
log_probs = log_probs.reshape(-1)
row_splits = hyps_shape.row_splits(1) * vocab_size
log_probs_shape = k2.ragged.create_ragged_shape2(
row_splits=row_splits, cached_tot_size=log_probs.numel()
)
ragged_log_probs = k2.RaggedTensor(
shape=log_probs_shape, value=log_probs
)
for i in range(batch_size):
topk_log_probs, topk_indexes = ragged_log_probs[i].topk(beam)
with warnings.catch_warnings():
warnings.simplefilter("ignore")
topk_hyp_indexes = (topk_indexes // vocab_size).tolist()
topk_token_indexes = (topk_indexes % vocab_size).tolist()
for k in range(len(topk_hyp_indexes)):
hyp_idx = topk_hyp_indexes[k]
hyp = A[i][hyp_idx]
new_ys = hyp.ys[:]
new_token = topk_token_indexes[k]
if new_token not in (blank_id, unk_id):
new_ys.append(new_token)
new_log_prob = topk_log_probs[k]
new_hyp = Hypothesis(ys=new_ys, log_prob=new_log_prob)
B[i].add(new_hyp)
B = B + finalized_B
best_hyps = [b.get_most_probable(length_norm=False) for b in B]
sorted_ans = [h.ys[context_size:] for h in best_hyps]
ans = []
unsorted_indices = packed_encoder_out.unsorted_indices.tolist()
for i in range(N):
ans.append(sorted_ans[unsorted_indices[i]])
return ans
def _deprecated_modified_beam_search(
model: Transducer,
encoder_out: torch.Tensor,
beam: int = 4,
) -> List[int]:
"""It limits the maximum number of symbols per frame to 1.
It decodes only one utterance at a time. We keep it only for reference.
The function :func:`modified_beam_search` should be preferred as it
supports batch decoding.
Args:
model:
An instance of `Transducer`.
encoder_out:
A tensor of shape (N, T, C) from the encoder. Support only N==1 for now.
beam:
Beam size.
Returns:
Return the decoded result.
"""
assert encoder_out.ndim == 3
# support only batch_size == 1 for now
assert encoder_out.size(0) == 1, encoder_out.size(0)
blank_id = model.decoder.blank_id
unk_id = getattr(model, "unk_id", blank_id)
context_size = model.decoder.context_size
device = next(model.parameters()).device
T = encoder_out.size(1)
B = HypothesisList()
B.add(
Hypothesis(
ys=[blank_id] * context_size,
log_prob=torch.zeros(1, dtype=torch.float32, device=device),
)
)
encoder_out = model.joiner.encoder_proj(encoder_out)
for t in range(T):
# fmt: off
current_encoder_out = encoder_out[:, t:t+1, :].unsqueeze(2)
# current_encoder_out is of shape (1, 1, 1, encoder_out_dim)
# fmt: on
A = list(B)
B = HypothesisList()
ys_log_probs = torch.cat([hyp.log_prob.reshape(1, 1) for hyp in A])
# ys_log_probs is of shape (num_hyps, 1)
decoder_input = torch.tensor(
[hyp.ys[-context_size:] for hyp in A],
device=device,
dtype=torch.int64,
)
# decoder_input is of shape (num_hyps, context_size)
decoder_out = model.decoder(decoder_input, need_pad=False).unsqueeze(1)
decoder_out = model.joiner.decoder_proj(decoder_out)
# decoder_output is of shape (num_hyps, 1, 1, joiner_dim)
current_encoder_out = current_encoder_out.expand(
decoder_out.size(0), 1, 1, -1
) # (num_hyps, 1, 1, encoder_out_dim)
logits = model.joiner(
current_encoder_out,
decoder_out,
project_input=False,
)
# logits is of shape (num_hyps, 1, 1, vocab_size)
logits = logits.squeeze(1).squeeze(1)
# now logits is of shape (num_hyps, vocab_size)
log_probs = logits.log_softmax(dim=-1)
log_probs.add_(ys_log_probs)
log_probs = log_probs.reshape(-1)
topk_log_probs, topk_indexes = log_probs.topk(beam)
# topk_hyp_indexes are indexes into `A`
topk_hyp_indexes = topk_indexes // logits.size(-1)
topk_token_indexes = topk_indexes % logits.size(-1)
with warnings.catch_warnings():
warnings.simplefilter("ignore")
topk_hyp_indexes = topk_hyp_indexes.tolist()
topk_token_indexes = topk_token_indexes.tolist()
for i in range(len(topk_hyp_indexes)):
hyp = A[topk_hyp_indexes[i]]
new_ys = hyp.ys[:]
new_token = topk_token_indexes[i]
if new_token not in (blank_id, unk_id):
new_ys.append(new_token)
new_log_prob = topk_log_probs[i]
new_hyp = Hypothesis(ys=new_ys, log_prob=new_log_prob)
B.add(new_hyp)
best_hyp = B.get_most_probable(length_norm=True)
ys = best_hyp.ys[context_size:] # [context_size:] to remove blanks
return ys
def beam_search(
model: Transducer,
encoder_out: torch.Tensor,
beam: int = 4,
) -> List[int]:
"""
It implements Algorithm 1 in https://arxiv.org/pdf/1211.3711.pdf
espnet/nets/beam_search_transducer.py#L247 is used as a reference.
Args:
model:
An instance of `Transducer`.
encoder_out:
A tensor of shape (N, T, C) from the encoder. Support only N==1 for now.
beam:
Beam size.
Returns:
Return the decoded result.
"""
assert encoder_out.ndim == 3
# support only batch_size == 1 for now
assert encoder_out.size(0) == 1, encoder_out.size(0)
blank_id = model.decoder.blank_id
unk_id = getattr(model, "unk_id", blank_id)
context_size = model.decoder.context_size
device = next(model.parameters()).device
decoder_input = torch.tensor(
[blank_id] * context_size,
device=device,
dtype=torch.int64,
).reshape(1, context_size)
decoder_out = model.decoder(decoder_input, need_pad=False)
decoder_out = model.joiner.decoder_proj(decoder_out)
encoder_out = model.joiner.encoder_proj(encoder_out)
T = encoder_out.size(1)
t = 0
B = HypothesisList()
B.add(Hypothesis(ys=[blank_id] * context_size, log_prob=0.0))
max_sym_per_utt = 20000
sym_per_utt = 0
decoder_cache: Dict[str, torch.Tensor] = {}
while t < T and sym_per_utt < max_sym_per_utt:
# fmt: off
current_encoder_out = encoder_out[:, t:t+1, :].unsqueeze(2)
# fmt: on
A = B
B = HypothesisList()
joint_cache: Dict[str, torch.Tensor] = {}
# TODO(fangjun): Implement prefix search to update the `log_prob`
# of hypotheses in A
while True:
y_star = A.get_most_probable()
A.remove(y_star)
cached_key = y_star.key
if cached_key not in decoder_cache:
decoder_input = torch.tensor(
[y_star.ys[-context_size:]],
device=device,
dtype=torch.int64,
).reshape(1, context_size)
decoder_out = model.decoder(decoder_input, need_pad=False)
decoder_out = model.joiner.decoder_proj(decoder_out)
decoder_cache[cached_key] = decoder_out
else:
decoder_out = decoder_cache[cached_key]
cached_key += f"-t-{t}"
if cached_key not in joint_cache:
logits = model.joiner(
current_encoder_out,
decoder_out.unsqueeze(1),
project_input=False,
)
# TODO(fangjun): Scale the blank posterior
log_prob = logits.log_softmax(dim=-1)
# log_prob is (1, 1, 1, vocab_size)
log_prob = log_prob.squeeze()
# Now log_prob is (vocab_size,)
joint_cache[cached_key] = log_prob
else:
log_prob = joint_cache[cached_key]
# First, process the blank symbol
skip_log_prob = log_prob[blank_id]
new_y_star_log_prob = y_star.log_prob + skip_log_prob
# ys[:] returns a copy of ys
B.add(Hypothesis(ys=y_star.ys[:], log_prob=new_y_star_log_prob))
# Second, process other non-blank labels
values, indices = log_prob.topk(beam + 1)
for i, v in zip(indices.tolist(), values.tolist()):
if i in (blank_id, unk_id):
continue
new_ys = y_star.ys + [i]
new_log_prob = y_star.log_prob + v
A.add(Hypothesis(ys=new_ys, log_prob=new_log_prob))
# Check whether B contains more than "beam" elements more probable
# than the most probable in A
A_most_probable = A.get_most_probable()
kept_B = B.filter(A_most_probable.log_prob)
if len(kept_B) >= beam:
B = kept_B.topk(beam)
break
t += 1
best_hyp = B.get_most_probable(length_norm=True)
ys = best_hyp.ys[context_size:] # [context_size:] to remove blanks
return ys

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../../../librispeech/ASR/pruned_transducer_stateless2/beam_search.py