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# 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.
from pathlib import Path
from typing import List, Union
import k2
import sentencepiece as spm
import torch
class BpeCtcTrainingGraphCompiler(object):
def __init__(
self,
lang_dir: Path,
device: Union[str, torch.device] = "cpu",
sos_token: str = "<sos/eos>",
eos_token: str = "<sos/eos>",
) -> None:
"""
Args:
lang_dir:
This directory is expected to contain the following files:
- bpe.model
- words.txt
device:
It indicates CPU or CUDA.
sos_token:
The word piece that represents sos.
eos_token:
The word piece that represents eos.
"""
lang_dir = Path(lang_dir)
model_file = lang_dir / "bpe.model"
sp = spm.SentencePieceProcessor()
sp.load(str(model_file))
self.sp = sp
self.word_table = k2.SymbolTable.from_file(lang_dir / "words.txt")
self.device = device
self.sos_id = self.sp.piece_to_id(sos_token)
self.eos_id = self.sp.piece_to_id(eos_token)
assert self.sos_id != self.sp.unk_id()
assert self.eos_id != self.sp.unk_id()
def texts_to_ids(self, texts: List[str]) -> List[List[int]]:
"""Convert a list of texts to a list-of-list of piece IDs.
Args:
texts:
It is a list of strings. Each string consists of space(s)
separated words. An example containing two strings is given below:
['HELLO ICEFALL', 'HELLO k2']
Returns:
Return a list-of-list of piece IDs.
"""
return self.sp.encode(texts, out_type=int)
def compile(
self,
piece_ids: List[List[int]],
modified: bool = False,
) -> k2.Fsa:
"""Build a ctc graph from a list-of-list piece IDs.
Args:
piece_ids:
It is a list-of-list integer IDs.
modified:
See :func:`k2.ctc_graph` for its meaning.
Return:
Return an FsaVec, which is the result of composing a
CTC topology with linear FSAs constructed from the given
piece IDs.
"""
graph = k2.ctc_graph(piece_ids, modified=modified, device=self.device)
return graph
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