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model_vq_vae.py
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model_vq_vae.py
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#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""Common PyTorch model training structure.
Author: Meng Cao
"""
import os
import torch
import torch.nn as nn
# import torch.optim as optim
# import numpy as np
from torch.utils.tensorboard import SummaryWriter
from torch.optim import AdamW, Adam
from torch.optim.lr_scheduler import ExponentialLR
from tqdm import tqdm
# from apex import amp
from transformers import WarmupLinearSchedule
from autoencoder_vq_vae import EmbeddingLayer, Encoder, Decoder, LinearSoftmax, EncoderDecoder, VectorQuantizer
class Model:
"""This class implements all model training and evluation methods.
"""
def __init__(self, args):
"""Initialize the model.
"""
self.args = args
self.logger = args.logger
# initialize model
self.model = self._build_model()
self.model.to(args.device)
# create optimizer and criterion
self.optimizer = self._get_optimizer(self.model.parameters())
self.scheduler = self._get_scheduler(self.optimizer)
self.criterion = self._get_criterion(pad_idx=args.pad_idx)
# Amp: Automatic Mixed Precision
if self.args.fp16:
self.model, self.optimizer = amp.initialize(self.model,
self.optimizer,
opt_level=args.fp16_opt_level)
self.logger.info("- Automatic Mixed Precision (AMP) is used.")
else:
self.logger.info("- NO Automatic Mixed Precision (AMP) available :/")
# multi-gpu training (should be after apex fp16 initialization)
if args.n_gpu > 1:
self.logger.info("- Let's use {} GPUs !".format(torch.cuda.device_count()))
self.model = nn.DataParallel(self.model)
else:
self.logger.info("- Train the model on single GPU :/")
# tensorboard
if args.write_summary:
self.writer = SummaryWriter(self.args.summary_path)
def _build_model(self):
"""Build auto-encoder model.
"""
embed = EmbeddingLayer(self.args.d_model,
self.args.vocab_size,
dropout=self.args.dropout)
encoder = Encoder(self.args.d_model,
self.args.N,
self.args.head_num,
self.args.d_ff,
self.args.hidden_size,
dropout=self.args.dropout)
decoder = Decoder(self.args.d_model,
self.args.N,
self.args.head_num,
self.args.d_ff,
self.args.hidden_size,
dropout=self.args.dropout)
linear_softmax = LinearSoftmax(self.args.d_model, self.args.vocab_size)
vectro_quantizer = VectorQuantizer(self.args.hidden_size,
self.args.num_embeddings,
self.args.commitment_cost)
model = EncoderDecoder(embed, encoder, decoder, linear_softmax, vectro_quantizer)
return model
def _initialize_params(self, model):
"""Initialize model parameters.
"""
for p in model.parameters():
if p.dim() > 1:
nn.init.xavier_uniform(p)
def _get_optimizer(self, optimizer_grouped_parameters):
"""Get optimizer for model training.
"""
if self.args.optimizer == 'adamw':
optimizer = AdamW(optimizer_grouped_parameters,
lr=self.args.learning_rate,
eps=self.args.adam_epsilon)
elif self.args.optimizer == 'adam':
optimizer = Adam(optimizer_grouped_parameters,
lr=self.args.learning_rate,
eps=self.args.adam_epsilon)
else:
raise Exception("Unknown optimizer type!")
return optimizer
def _get_scheduler(self, optimizer):
"""Get scheduler for adjusting learning rate.
"""
if self.args.scheduler == 'warmup':
scheduler = WarmupLinearSchedule(optimizer,
warmup_steps=self.args.warmup_steps,
t_total=self.args.num_epochs)
elif self.args.scheduler == 'exponential':
scheduler = ExponentialLR(optimizer, 0.95)
return scheduler
def _get_criterion(self, pad_idx=None):
"""Implement loss function.
"""
if self.args.ignore_pad_idx and pad_idx is not None:
return nn.NLLLoss(ignore_index=pad_idx)
else:
self.logger.info("- WARNNING: no pad-index ignored during training!")
return nn.NLLLoss()
def load_weights(self, path):
"""Load pre-trained weights.
"""
self.model.load_state_dict(torch.load(path))
def save_model(self, save_dir):
"""Save the model.
"""
if not os.path.exists(save_dir):
os.makedirs(save_dir)
model_path = os.path.join(save_dir + 'checkpoint.pth.tar')
torch.save(self.model.state_dict(), model_path)
def _build_mask(self, inputs, pad_idx=0):
"""Build mask for input sequence.
Args:
inputs: [batch_size, seq_len]
"""
en_mask = torch.ones_like(inputs, dtype=inputs.dtype, device=self.args.device)
en_mask.masked_fill_(inputs == pad_idx, 0)
return en_mask
def loss_batch(self, inputs, labels, optimizer=None, step=None):
"""Compute loss and update model weights on a batch of data.
Args:
inputs: [batch_size, seq_len]
labels: [batch_size, seq_len]
Returns:
loss: float
log_probs: [batch_size, seq_len, vocab_size]
"""
mask = self._build_mask(inputs, self.args.pad_idx)
log_probs, vq_vae_loss = self.model(inputs, mask) # outputs: [N, S, vocab_size]
loss = self.criterion(log_probs.transpose(1, 2), labels) + vq_vae_loss.mean()
if self.args.n_gpu > 1:
loss = loss.mean() # mean() to average on multi-gpu parallel training
if self.args.gradient_accumulation_steps > 1:
loss = loss / self.args.gradient_accumulation_steps
if optimizer is not None:
loss.backward() # compute gradients
if (step + 1) % self.args.gradient_accumulation_steps == 0:
nn.utils.clip_grad_norm_(self.model.parameters(),
self.args.max_grad_norm)
optimizer.step() # update model parameters
optimizer.zero_grad() # clean all gradients
return loss.item(), log_probs.detach()
def train_epoch(self, train_dataloader, optimizer, epoch):
"""Train the model for one single epoch.
"""
self.model.train()
epoch_iterator = tqdm(train_dataloader, desc="Iteration")
train_loss = 0.0
for i, batch in enumerate(epoch_iterator):
batch = {k: v.to(self.args.device) for k, v in batch.items()}
batch_loss, _ = self.loss_batch(batch['target'],
batch['target'],
optimizer=optimizer,
step=i)
train_loss += batch_loss
if self.writer:
self.writer.add_scalar('batch_loss',
batch_loss,
epoch * len(train_dataloader) + i + 1)
# compute the average loss
epoch_loss = train_loss / len(train_dataloader)
# update scheduler
self.scheduler.step()
return epoch_loss
def evaluate(self, eval_dataloader, print_report=False):
"""Evaluate the model, return average loss and accuracy.
"""
self.model.eval()
epoch_iterator = tqdm(eval_dataloader, desc="Iteration")
with torch.no_grad():
eval_loss, eval_corrects = 0., 0.
for i, batch in enumerate(epoch_iterator):
batch = {k: v.to(self.args.device) for k, v in batch.items()}
batch_loss, outputs = self.loss_batch(batch['target'],
batch['target'])
_, preds = torch.max(outputs, -1) # preds: [batch_size, seq_len]
if i in range(3):
print("- Example #{}: ".format(i+1))
print("- {}".format(preds[i][:batch['length'][i]].tolist()))
print("- {}".format(batch['target'][i][:batch['length'][i]].tolist()))
eval_loss += batch_loss
batch_correct = 0.
for p, t, l in zip(preds, batch['target'], batch['length']):
batch_correct += torch.sum(p[:l] == t[:l]).item()
eval_corrects += batch_correct / torch.sum(batch['length']).item()
# update metrics
avg_loss = eval_loss / len(eval_dataloader)
avg_acc = eval_corrects / len(eval_dataloader)
return avg_loss, avg_acc
def fit(self, train_dataloader, eval_dataloader):
"""Model training.
"""
best_acc = 0.
num_epochs = self.args.num_epochs
for epoch in range(num_epochs):
self.logger.info('Epoch {}/{}'.format(epoch, num_epochs - 1))
# train
train_loss = self.train_epoch(train_dataloader, self.optimizer, epoch)
self.logger.info("Traing Loss: {}".format(train_loss))
# evaluation
eval_loss, eval_acc = self.evaluate(eval_dataloader, print_report=True)
self.logger.info("Evaluation:")
self.logger.info("- loss: {}".format(eval_loss))
self.logger.info("- acc: {}".format(eval_acc))
# monitor loss and accuracy
if self.writer:
self.writer.add_scalar('epoch_loss', train_loss, epoch)
self.writer.add_scalar('eval_loss', eval_loss, epoch)
self.writer.add_scalar('eval_acc', eval_acc, epoch)
self.writer.add_scalar('lr', self.scheduler.get_lr()[0], epoch)
# save the best model
if eval_acc >= best_acc:
best_acc = eval_acc
self.logger.info("New best score!")
self.save_model(self.args.save_dir)
self.logger.info("- model is saved at: {}".format(self.args.save_dir))
def predict(self, inputs):
"""Model inference.
Args:
inputs: [batch_size, seq_len]
outputs: [batch_size, seq_len]
"""
self.model.eval()
with torch.no_grad():
mask = self._build_mask(inputs, self.args.pad_idx)
log_probs, _ = self.model(inputs, mask) # outputs: [batch_size, seq_len, vocab_size]
_, preds = torch.max(log_probs, -1) # preds: [batch_size, seq_len]
return preds