from abc import ABC
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from abc import abstractmethod
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from typing import Tuple
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import torch
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from funasr.modules.scorers.scorer_interface import BatchScorerInterface
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from typing import Dict
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from typing import Optional
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from typing import Tuple
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import torch
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import torch.nn.functional as F
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from typeguard import check_argument_types
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from funasr.modules.nets_utils import make_pad_mask
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from funasr.torch_utils.device_funcs import force_gatherable
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from funasr.models.base_model import FunASRModel
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class AbsLM(torch.nn.Module, BatchScorerInterface, ABC):
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"""The abstract LM class
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To share the loss calculation way among different models,
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We uses delegate pattern here:
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The instance of this class should be passed to "LanguageModel"
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>>> from funasr.lm.abs_model import AbsLM
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>>> lm = AbsLM()
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>>> model = LanguageESPnetModel(lm=lm)
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This "model" is one of mediator objects for "Task" class.
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"""
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@abstractmethod
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def forward(
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self, input: torch.Tensor, hidden: torch.Tensor
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) -> Tuple[torch.Tensor, torch.Tensor]:
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raise NotImplementedError
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class LanguageModel(FunASRModel):
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def __init__(self, lm: AbsLM, vocab_size: int, ignore_id: int = 0):
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assert check_argument_types()
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super().__init__()
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self.lm = lm
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self.sos = 1
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self.eos = 2
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# ignore_id may be assumed as 0, shared with CTC-blank symbol for ASR.
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self.ignore_id = ignore_id
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def nll(
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self,
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text: torch.Tensor,
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text_lengths: torch.Tensor,
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max_length: Optional[int] = None,
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) -> Tuple[torch.Tensor, torch.Tensor]:
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"""Compute negative log likelihood(nll)
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Normally, this function is called in batchify_nll.
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Args:
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text: (Batch, Length)
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text_lengths: (Batch,)
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max_lengths: int
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"""
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batch_size = text.size(0)
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# For data parallel
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if max_length is None:
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text = text[:, : text_lengths.max()]
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else:
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text = text[:, :max_length]
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# 1. Create a sentence pair like '<sos> w1 w2 w3' and 'w1 w2 w3 <eos>'
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# text: (Batch, Length) -> x, y: (Batch, Length + 1)
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x = F.pad(text, [1, 0], "constant", self.sos)
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t = F.pad(text, [0, 1], "constant", self.ignore_id)
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for i, l in enumerate(text_lengths):
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t[i, l] = self.eos
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x_lengths = text_lengths + 1
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# 2. Forward Language model
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# x: (Batch, Length) -> y: (Batch, Length, NVocab)
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y, _ = self.lm(x, None)
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# 3. Calc negative log likelihood
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# nll: (BxL,)
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nll = F.cross_entropy(y.view(-1, y.shape[-1]), t.view(-1), reduction="none")
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# nll: (BxL,) -> (BxL,)
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if max_length is None:
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nll.masked_fill_(make_pad_mask(x_lengths).to(nll.device).view(-1), 0.0)
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else:
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nll.masked_fill_(
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make_pad_mask(x_lengths, maxlen=max_length + 1).to(nll.device).view(-1),
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0.0,
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)
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# nll: (BxL,) -> (B, L)
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nll = nll.view(batch_size, -1)
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return nll, x_lengths
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def batchify_nll(
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self, text: torch.Tensor, text_lengths: torch.Tensor, batch_size: int = 100
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) -> Tuple[torch.Tensor, torch.Tensor]:
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"""Compute negative log likelihood(nll) from transformer language model
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To avoid OOM, this fuction seperate the input into batches.
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Then call nll for each batch and combine and return results.
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Args:
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text: (Batch, Length)
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text_lengths: (Batch,)
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batch_size: int, samples each batch contain when computing nll,
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you may change this to avoid OOM or increase
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"""
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total_num = text.size(0)
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if total_num <= batch_size:
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nll, x_lengths = self.nll(text, text_lengths)
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else:
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nlls = []
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x_lengths = []
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max_length = text_lengths.max()
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start_idx = 0
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while True:
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end_idx = min(start_idx + batch_size, total_num)
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batch_text = text[start_idx:end_idx, :]
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batch_text_lengths = text_lengths[start_idx:end_idx]
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# batch_nll: [B * T]
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batch_nll, batch_x_lengths = self.nll(
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batch_text, batch_text_lengths, max_length=max_length
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)
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nlls.append(batch_nll)
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x_lengths.append(batch_x_lengths)
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start_idx = end_idx
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if start_idx == total_num:
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break
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nll = torch.cat(nlls)
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x_lengths = torch.cat(x_lengths)
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assert nll.size(0) == total_num
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assert x_lengths.size(0) == total_num
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return nll, x_lengths
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def forward(
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self, text: torch.Tensor, text_lengths: torch.Tensor
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) -> Tuple[torch.Tensor, Dict[str, torch.Tensor], torch.Tensor]:
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nll, y_lengths = self.nll(text, text_lengths)
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ntokens = y_lengths.sum()
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loss = nll.sum() / ntokens
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stats = dict(loss=loss.detach())
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# force_gatherable: to-device and to-tensor if scalar for DataParallel
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loss, stats, weight = force_gatherable((loss, stats, ntokens), loss.device)
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return loss, stats, weight
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def collect_feats(
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self, text: torch.Tensor, text_lengths: torch.Tensor
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) -> Dict[str, torch.Tensor]:
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return {}
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