mirror of
https://github.com/huggingface/transformers.git
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432 lines
19 KiB
Python
432 lines
19 KiB
Python
import os
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import math
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from tensorboardX import SummaryWriter
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from tqdm import trange, tqdm
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import numpy as np
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import torch
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import torch.nn as nn
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import torch.nn.functional as F
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from pytorch_transformers import AdamW, WarmupLinearSchedule
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from utils import logger
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from dataset import Dataset
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class Distiller:
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def __init__(self,
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params: dict,
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dataloader: Dataset,
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token_probs: torch.tensor,
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student: nn.Module,
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teacher: nn.Module):
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logger.info('Initializing Distiller')
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self.params = params
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self.dump_path = params.dump_path
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self.multi_gpu = params.multi_gpu
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self.fp16 = params.fp16
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self.student = student
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self.teacher = teacher
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self.dataloader = dataloader
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if self.params.n_gpu > 1:
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self.dataloader.split()
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self.get_iterator(seed=params.seed)
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self.temperature = params.temperature
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assert self.temperature > 0.
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self.alpha_ce = params.alpha_ce
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self.alpha_mlm = params.alpha_mlm
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self.alpha_mse = params.alpha_mse
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assert self.alpha_ce >= 0.
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assert self.alpha_mlm >= 0.
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assert self.alpha_mse >= 0.
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assert self.alpha_ce + self.alpha_mlm + self.alpha_mse > 0.
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self.mlm_mask_prop = params.mlm_mask_prop
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assert 0.0 <= self.mlm_mask_prop <= 1.0
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assert params.word_mask + params.word_keep + params.word_rand == 1.0
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self.pred_probs = torch.FloatTensor([params.word_mask, params.word_keep, params.word_rand])
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self.pred_probs = self.pred_probs.to(f'cuda:{params.local_rank}') if params.n_gpu > 0 else self.pred_probs
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self.token_probs = token_probs.to(f'cuda:{params.local_rank}') if params.n_gpu > 0 else token_probs
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if self.fp16:
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self.pred_probs = self.pred_probs.half()
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self.token_probs = self.token_probs.half()
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self.epoch = 0
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self.n_iter = 0
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self.n_total_iter = 0
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self.n_sequences_epoch = 0
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self.total_loss_epoch = 0
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self.last_loss = 0
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self.last_loss_ce = 0
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self.last_loss_mlm = 0
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self.last_loss_mse = 0
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self.ce_loss_fct = nn.KLDivLoss(reduction='batchmean')
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self.mlm_loss_fct = nn.CrossEntropyLoss(ignore_index=-1)
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self.mse_loss_fct = nn.MSELoss(reduction='sum')
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logger.info('--- Initializing model optimizer')
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assert params.gradient_accumulation_steps >= 1
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self.num_steps_epoch = int(len(self.dataloader) / params.batch_size) + 1
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num_train_optimization_steps = int(self.num_steps_epoch / params.gradient_accumulation_steps * params.n_epoch) + 1
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warmup_steps = math.ceil(num_train_optimization_steps * params.warmup_prop)
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no_decay = ['bias', 'LayerNorm.weight']
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optimizer_grouped_parameters = [
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{'params': [p for n, p in student.named_parameters() if not any(nd in n for nd in no_decay) and p.requires_grad], 'weight_decay': params.weight_decay},
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{'params': [p for n, p in student.named_parameters() if any(nd in n for nd in no_decay) and p.requires_grad], 'weight_decay': 0.0}
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]
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logger.info("------ Number of trainable parameters (student): %i" % sum([p.numel() for p in self.student.parameters() if p.requires_grad]))
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logger.info("------ Number of parameters (student): %i" % sum([p.numel() for p in self.student.parameters()]))
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self.optimizer = AdamW(optimizer_grouped_parameters,
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lr=params.learning_rate,
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eps=params.adam_epsilon,
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betas=(0.9, 0.98))
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self.scheduler = WarmupLinearSchedule(self.optimizer,
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warmup_steps=warmup_steps,
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t_total=num_train_optimization_steps)
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if self.fp16:
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try:
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from apex import amp
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except ImportError:
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raise ImportError("Please install apex from https://www.github.com/nvidia/apex to use fp16 training.")
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logger.info(f"Using fp16 training: {self.params.fp16_opt_level} level")
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self.student, self.optimizer = amp.initialize(self.student,
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self.optimizer,
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opt_level=self.params.fp16_opt_level)
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self.teacher = self.teacher.half()
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if self.multi_gpu:
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if self.fp16:
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from apex.parallel import DistributedDataParallel
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logger.info("Using apex.parallel.DistributedDataParallel for distributed training.")
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self.student = DistributedDataParallel(self.student)
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else:
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from torch.nn.parallel import DistributedDataParallel
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logger.info("Using nn.parallel.DistributedDataParallel for distributed training.")
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self.student = DistributedDataParallel(self.student,
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device_ids=[params.local_rank],
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output_device=params.local_rank)
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self.is_master = params.is_master
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if self.is_master:
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logger.info('--- Initializing Tensorboard')
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self.tensorboard = SummaryWriter(log_dir=os.path.join(self.dump_path, 'log', 'train'))
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self.tensorboard.add_text(tag='config', text_string=str(self.params), global_step=0)
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def get_iterator(self,
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seed: int = None):
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"""
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Initialize the data iterator.
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Each process has its own data iterator (iterating on his own random portion of the dataset).
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Input:
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------
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seed: `int` - The random seed.
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"""
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logger.info('--- Initializing Data Iterator')
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self.data_iterator = self.dataloader.get_iterator(seed=seed)
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def get_batch(self):
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"""
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Call the data iterator to output a new batch.
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If the data iterator went through the whole dataset, create a new iterator.
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"""
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assert hasattr(self, 'data_iterator')
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try:
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x = next(self.data_iterator)
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except StopIteration:
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logger.warning('--- Went through the whole dataset. Creating new data iterator.')
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self.data_iterator = self.dataloader.get_iterator()
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x = next(self.data_iterator)
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return x
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def prepare_batch(self,
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batch):
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"""
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Prepare the batch: from the token_ids and the lenghts, compute the attention mask and the masked label for MLM.
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Input:
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------
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batch: `Tuple`
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token_ids: `torch.tensor(bs, seq_length)` - The token ids for each of the sequence. It is padded.
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lengths: `torch.tensor(bs)` - The lengths of each of the sequences in the batch.
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Output:
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-------
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token_ids: `torch.tensor(bs, seq_length)` - The token ids after the modifications for MLM.
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attn_mask: `torch.tensor(bs, seq_length)` - The attention mask for the self-attention.
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mlm_labels: `torch.tensor(bs, seq_length)` - The masked languge modeling labels. There is a -1 where there is nothing to predict.
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"""
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token_ids, lengths = batch
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token_ids, lengths = self.round_batch(x=token_ids, lengths=lengths)
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assert token_ids.size(0) == lengths.size(0)
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attn_mask = (torch.arange(token_ids.size(1), dtype=torch.long, device=lengths.device) < lengths[:, None])
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bs, max_seq_len = token_ids.size()
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mlm_labels = token_ids.new(token_ids.size()).copy_(token_ids)
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x_prob = self.token_probs[token_ids.flatten()]
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n_tgt = math.ceil(self.mlm_mask_prop * lengths.sum().item())
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tgt_ids = torch.multinomial(x_prob / x_prob.sum(), n_tgt, replacement=False)
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pred_mask = torch.zeros(bs * max_seq_len, dtype=torch.uint8, device=token_ids.device)
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pred_mask[tgt_ids] = 1
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pred_mask = pred_mask.view(bs, max_seq_len)
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pred_mask[token_ids == self.params.special_tok_ids['pad_token']] = 0
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# mask a number of words == 0 [8] (faster with fp16)
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if self.fp16:
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n1 = pred_mask.sum().item()
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if n1 > 8:
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pred_mask = pred_mask.view(-1)
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n2 = max(n1 % 8, 8 * (n1 // 8))
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if n2 != n1:
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pred_mask[torch.nonzero(pred_mask).view(-1)[:n1-n2]] = 0
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pred_mask = pred_mask.view(bs, max_seq_len)
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assert pred_mask.sum().item() % 8 == 0, pred_mask.sum().item()
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_token_ids_real = token_ids[pred_mask]
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_token_ids_rand = _token_ids_real.clone().random_(self.params.vocab_size)
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_token_ids_mask = _token_ids_real.clone().fill_(self.params.special_tok_ids['mask_token'])
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probs = torch.multinomial(self.pred_probs, len(_token_ids_real), replacement=True)
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_token_ids = _token_ids_mask * (probs == 0).long() + _token_ids_real * (probs == 1).long() + _token_ids_rand * (probs == 2).long()
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token_ids = token_ids.masked_scatter(pred_mask, _token_ids)
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mlm_labels[1-pred_mask] = -1
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return token_ids, attn_mask, mlm_labels
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def round_batch(self,
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x: torch.tensor,
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lengths: torch.tensor):
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"""
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For float16 only.
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Sub-sample sentences in a batch, and add padding, so that each dimension is a multiple of 8.
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Input:
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------
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x: `torch.tensor(bs, seq_length)` - The token ids.
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lengths: `torch.tensor(bs, seq_length)` - The lengths of each of the sequence in the batch.
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Output:
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-------
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x: `torch.tensor(new_bs, new_seq_length)` - The updated token ids.
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lengths: `torch.tensor(new_bs, new_seq_length)` - The updated lengths.
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"""
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if not self.fp16 or len(lengths) < 8:
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return x, lengths
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# number of sentences == 0 [8]
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bs1 = len(lengths)
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bs2 = 8 * (bs1 // 8)
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assert bs2 > 0 and bs2 % 8 == 0
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if bs1 != bs2:
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idx = torch.randperm(bs1)[:bs2]
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lengths = lengths[idx]
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slen = lengths.max().item()
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x = x[idx, :slen]
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else:
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idx = None
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# sequence length == 0 [8]
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ml1 = x.size(1)
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if ml1 % 8 != 0:
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pad = 8 - (ml1 % 8)
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ml2 = ml1 + pad
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pad_id = self.params.special_tok_ids['pad_token']
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padding_tensor = torch.zeros(bs2, pad, dtype=torch.long, device=x.device).fill_(pad_id)
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x = torch.cat([x, padding_tensor], 1)
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assert x.size() == (bs2, ml2)
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assert x.size(0) % 8 == 0
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assert x.size(1) % 8 == 0
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return x, lengths
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def train(self):
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"""
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The real training loop.
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"""
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if self.is_master: logger.info('Starting training')
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self.student.train()
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self.teacher.eval()
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for _ in range(self.params.n_epoch):
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if self.is_master: logger.info(f'--- Starting epoch {self.epoch}/{self.params.n_epoch-1}')
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iter_bar = trange(self.num_steps_epoch, desc="-Iter", disable=self.params.local_rank not in [-1, 0])
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for __ in range(self.num_steps_epoch):
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batch = self.get_batch()
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if self.params.n_gpu > 0:
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batch = tuple(t.to(f'cuda:{self.params.local_rank}') for t in batch)
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token_ids, attn_mask, mlm_labels = self.prepare_batch(batch=batch)
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self.step(input_ids=token_ids, attention_mask=attn_mask, mlm_labels=mlm_labels)
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iter_bar.update()
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iter_bar.set_postfix({'Last_loss': f'{self.last_loss:.2f}',
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'Avg_cum_loss': f'{self.total_loss_epoch/self.n_iter:.2f}'})
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iter_bar.close()
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if self.is_master: logger.info(f'--- Ending epoch {self.epoch}/{self.params.n_epoch-1}')
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self.end_epoch()
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if self.is_master: logger.info('Training is finished')
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def step(self,
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input_ids: torch.tensor,
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attention_mask: torch.tensor,
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mlm_labels: torch.tensor):
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"""
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One optimization step: forward of student AND teacher, backward on the loss (for gradient accumulation),
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and possibly a parameter update (depending on the gradient accumulation).
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Input:
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------
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input_ids: `torch.tensor(bs, seq_length)` - The token ids.
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attention_mask: `torch.tensor(bs, seq_length)` - The attention mask for self attention.
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mlm_labels: `torch.tensor(bs, seq_length)` - The masked language modeling labels.
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"""
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s_logits = self.student(input_ids=input_ids, attention_mask=attention_mask)[0] # (bs, seq_length, voc_size)
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with torch.no_grad():
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t_logits = self.teacher(input_ids=input_ids, attention_mask=attention_mask)[0] # (bs, seq_length, voc_size)
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assert s_logits.size() == t_logits.size()
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#https://github.com/peterliht/knowledge-distillation-pytorch/blob/master/model/net.py#L100
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#https://github.com/peterliht/knowledge-distillation-pytorch/issues/2
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if self.params.restrict_ce_to_mask:
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mask = (mlm_labels>-1).unsqueeze(-1).expand_as(s_logits) # (bs, seq_lenth, voc_size)
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else:
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mask = attention_mask.unsqueeze(-1).expand_as(s_logits) # (bs, seq_lenth, voc_size)
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s_logits_slct = torch.masked_select(s_logits, mask) # (bs * seq_length * voc_size) modulo the 1s in mask
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s_logits_slct = s_logits_slct.view(-1, s_logits.size(-1)) # (bs * seq_length, voc_size) modulo the 1s in mask
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t_logits_slct = torch.masked_select(t_logits, mask) # (bs * seq_length * voc_size) modulo the 1s in mask
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t_logits_slct = t_logits_slct.view(-1, s_logits.size(-1)) # (bs * seq_length, voc_size) modulo the 1s in mask
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assert t_logits_slct.size() == s_logits_slct.size()
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loss_ce = self.ce_loss_fct(F.log_softmax(s_logits_slct/self.temperature, dim=-1),
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F.softmax(t_logits_slct/self.temperature, dim=-1)) * (self.temperature)**2
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loss = self.alpha_ce*loss_ce
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if self.alpha_mlm > 0.:
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loss_mlm = self.mlm_loss_fct(s_logits.view(-1, s_logits.size(-1)), mlm_labels.view(-1))
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loss += self.alpha_mlm * loss_mlm
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if self.alpha_mse > 0.:
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loss_mse = self.mse_loss_fct(s_logits_slct, t_logits_slct)/s_logits_slct.size(0) # Reproducing batchmean reduction
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loss += self.alpha_mse * loss_mse
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self.total_loss_epoch += loss.item()
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self.last_loss = loss.item()
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self.last_loss_ce = loss_ce.item()
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if self.alpha_mlm > 0.:
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self.last_loss_mlm = loss_mlm.item()
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if self.alpha_mse > 0.:
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self.last_loss_mse = loss_mse.item()
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self.optimize(loss)
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self.n_sequences_epoch += input_ids.size(0)
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def optimize(self,
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loss):
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"""
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Normalization on the loss (gradient accumulation or distributed training), followed by
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backward pass on the loss, possibly followed by a parameter update (depending on the gradient accumulation).
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Also update the metrics for tensorboard.
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"""
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# Check for NaN
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if (loss != loss).data.any():
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logger.error('NaN detected')
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exit()
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if self.multi_gpu:
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loss = loss.mean()
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if self.params.gradient_accumulation_steps > 1:
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loss = loss / self.params.gradient_accumulation_steps
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if self.fp16:
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from apex import amp
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with amp.scale_loss(loss, self.optimizer) as scaled_loss:
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scaled_loss.backward()
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else:
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loss.backward()
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self.iter()
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if self.n_iter % self.params.gradient_accumulation_steps == 0:
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if self.fp16:
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torch.nn.utils.clip_grad_norm_(amp.master_params(self.optimizer), self.params.max_grad_norm)
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else:
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torch.nn.utils.clip_grad_norm_(self.student.parameters(), self.params.max_grad_norm)
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self.scheduler.step()
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self.optimizer.step()
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self.optimizer.zero_grad()
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def iter(self):
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"""
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Update global counts, write to tensorboard and save checkpoint.
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"""
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self.n_iter += 1
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self.n_total_iter += 1
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if self.n_total_iter % self.params.log_interval == 0:
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self.log_tensorboard()
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if self.n_total_iter % self.params.checkpoint_interval == 0:
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self.save_checkpoint()
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def log_tensorboard(self):
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"""
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Log into tensorboard. Only by the master process.
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"""
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if not self.is_master:
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return
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for param_name, param in self.student.named_parameters():
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self.tensorboard.add_scalar(tag='parameter_mean/' + param_name, scalar_value=param.data.mean(), global_step=self.n_total_iter)
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self.tensorboard.add_scalar(tag='parameter_std/' + param_name, scalar_value=param.data.std(), global_step=self.n_total_iter)
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if param.grad is None:
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continue
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self.tensorboard.add_scalar(tag="grad_mean/" + param_name, scalar_value=param.grad.data.mean(),global_step=self.n_total_iter)
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self.tensorboard.add_scalar(tag="grad_std/" + param_name, scalar_value=param.grad.data.std(), global_step=self.n_total_iter)
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self.tensorboard.add_scalar(tag="losses/cum_avg_loss_epoch", scalar_value=self.total_loss_epoch/self.n_iter, global_step=self.n_total_iter)
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self.tensorboard.add_scalar(tag="losses/loss", scalar_value=self.last_loss, global_step=self.n_total_iter)
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self.tensorboard.add_scalar(tag="losses/loss_ce", scalar_value=self.last_loss_ce, global_step=self.n_total_iter)
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if self.alpha_mlm > 0.:
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self.tensorboard.add_scalar(tag="losses/loss_mlm", scalar_value=self.last_loss_mlm, global_step=self.n_total_iter)
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if self.alpha_mse > 0.:
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self.tensorboard.add_scalar(tag="losses/loss_mse", scalar_value=self.last_loss_mse, global_step=self.n_total_iter)
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self.tensorboard.add_scalar(tag="learning_rate/lr", scalar_value=self.scheduler.get_lr()[0], global_step=self.n_total_iter)
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def end_epoch(self):
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"""
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Finally arrived at the end of epoch (full pass on dataset).
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Do some tensorboard logging and checkpoint saving.
|
|
"""
|
|
logger.info(f'{self.n_sequences_epoch} sequences have been trained during this epoch.')
|
|
|
|
if self.is_master:
|
|
self.save_checkpoint(checkpoint_name=f'model_epoch_{self.epoch}.pth')
|
|
self.tensorboard.add_scalar(tag='epoch/loss', scalar_value=self.total_loss_epoch/self.n_iter, global_step=self.epoch)
|
|
|
|
self.epoch += 1
|
|
self.n_sequences_epoch = 0
|
|
self.n_iter = 0
|
|
self.total_loss_epoch = 0
|
|
|
|
def save_checkpoint(self,
|
|
checkpoint_name: str = 'checkpoint.pth'):
|
|
"""
|
|
Save the current state. Only by the master process.
|
|
"""
|
|
if not self.is_master:
|
|
return
|
|
mdl_to_save = self.student.module if hasattr(self.student, 'module') else self.student
|
|
mdl_to_save.config.save_pretrained(self.dump_path)
|
|
state_dict = mdl_to_save.state_dict()
|
|
torch.save(state_dict, os.path.join(self.dump_path, checkpoint_name))
|