import os
from abc import ABCMeta, abstractmethod
from pathlib import Path
import numpy as np
import torch
import torch.nn as nn
import torch.nn.functional as F
from sklearn.metrics import accuracy_score, f1_score
from torch.nn.utils.rnn import pad_sequence
from tqdm import tqdm
import quapy as qp
from quapy.data import LabelledCollection
from quapy.util import EarlyStop
class NeuralClassifierTrainer:
"""
Trains a neural network for text classification.
:param net: an instance of `TextClassifierNet` implementing the forward pass
:param lr: learning rate (default 1e-3)
:param weight_decay: weight decay (default 0)
:param patience: number of epochs that do not show any improvement in validation
to wait before applying early stop (default 10)
:param epochs: maximum number of training epochs (default 200)
:param batch_size: batch size for training (default 64)
:param batch_size_test: batch size for test (default 512)
:param padding_length: maximum number of tokens to consider in a document (default 300)
:param device: specify 'cpu' (default) or 'cuda' for enabling gpu
:param checkpointpath: where to store the parameters of the best model found so far
according to the evaluation in the held-out validation split (default '../checkpoint/classifier_net.dat')
"""
def __init__(self,
net: 'TextClassifierNet',
lr=1e-3,
weight_decay=0,
patience=10,
epochs=200,
batch_size=64,
batch_size_test=512,
padding_length=300,
device='cuda',
checkpointpath='../checkpoint/classifier_net.dat'):
super().__init__()
assert isinstance(net, TextClassifierNet), f'net is not an instance of {TextClassifierNet.__name__}'
self.net = net.to(device)
self.vocab_size = self.net.vocabulary_size
self.trainer_hyperparams={
'lr': lr,
'weight_decay': weight_decay,
'patience': patience,
'epochs': epochs,
'batch_size': batch_size,
'batch_size_test': batch_size_test,
'padding_length': padding_length,
'device': torch.device(device)
}
self.learner_hyperparams = self.net.get_params()
self.checkpointpath = checkpointpath
print(f'[NeuralNetwork running on {device}]')
os.makedirs(Path(checkpointpath).parent, exist_ok=True)
def reset_net_params(self, vocab_size, n_classes):
"""Reinitialize the network parameters
:param vocab_size: the size of the vocabulary
:param n_classes: the number of target classes
"""
self.net = self.net.__class__(vocab_size, n_classes, **self.learner_hyperparams)
self.net = self.net.to(self.trainer_hyperparams['device'])
self.net.xavier_uniform()
def get_params(self):
"""Get hyper-parameters for this estimator
:return: a dictionary with parameter names mapped to their values
"""
return {**self.net.get_params(), **self.trainer_hyperparams}
def set_params(self, **params):
"""Set the parameters of this trainer and the learner it is training.
In this current version, parameter names for the trainer and learner should
be disjoint.
:param params: a `**kwargs` dictionary with the parameters
"""
trainer_hyperparams = self.trainer_hyperparams
learner_hyperparams = self.net.get_params()
for key, val in params.items():
if key in trainer_hyperparams and key in learner_hyperparams:
raise ValueError(f'the use of parameter {key} is ambiguous since it can refer to '
f'a parameters of the Trainer or the learner {self.net.__name__}')
elif key not in trainer_hyperparams and key not in learner_hyperparams:
raise ValueError(f'parameter {key} is not valid')
if key in trainer_hyperparams:
trainer_hyperparams[key] = val
else:
learner_hyperparams[key] = val
self.trainer_hyperparams = trainer_hyperparams
self.learner_hyperparams = learner_hyperparams
@property
def device(self):
""" Gets the device in which the network is allocated
:return: device
"""
return next(self.net.parameters()).device
def _train_epoch(self, data, status, pbar, epoch):
self.net.train()
criterion = torch.nn.CrossEntropyLoss()
losses, predictions, true_labels = [], [], []
for xi, yi in data:
self.optim.zero_grad()
logits = self.net.forward(xi)
loss = criterion(logits, yi)
loss.backward()
self.optim.step()
losses.append(loss.item())
preds = torch.softmax(logits, dim=-1).detach().cpu().numpy().argmax(axis=-1)
status["loss"] = np.mean(losses)
predictions.extend(preds.tolist())
true_labels.extend(yi.detach().cpu().numpy().tolist())
status["acc"] = accuracy_score(true_labels, predictions)
status["f1"] = f1_score(true_labels, predictions, average='macro')
self.__update_progress_bar(pbar, epoch)
def _test_epoch(self, data, status, pbar, epoch):
self.net.eval()
criterion = torch.nn.CrossEntropyLoss()
losses, predictions, true_labels = [], [], []
with torch.no_grad():
for xi, yi in data:
logits = self.net.forward(xi)
loss = criterion(logits, yi)
losses.append(loss.item())
preds = torch.softmax(logits, dim=-1).detach().cpu().numpy().argmax(axis=-1)
predictions.extend(preds.tolist())
true_labels.extend(yi.detach().cpu().numpy().tolist())
status["loss"] = np.mean(losses)
status["acc"] = accuracy_score(true_labels, predictions)
status["f1"] = f1_score(true_labels, predictions, average='macro')
self.__update_progress_bar(pbar, epoch)
def __update_progress_bar(self, pbar, epoch):
pbar.set_description(f'[{self.net.__class__.__name__}] training epoch={epoch} '
f'tr-loss={self.status["tr"]["loss"]:.5f} '
f'tr-acc={100 * self.status["tr"]["acc"]:.2f}% '
f'tr-macroF1={100 * self.status["tr"]["f1"]:.2f}% '
f'patience={self.early_stop.patience}/{self.early_stop.PATIENCE_LIMIT} '
f'val-loss={self.status["va"]["loss"]:.5f} '
f'val-acc={100 * self.status["va"]["acc"]:.2f}% '
f'macroF1={100 * self.status["va"]["f1"]:.2f}%')
def fit(self, instances, labels, val_split=0.3):
"""
Fits the model according to the given training data.
:param instances: list of lists of indexed tokens
:param labels: array-like of shape `(n_samples, n_classes)` with the class labels
:param val_split: proportion of training documents to be taken as the validation set (default 0.3)
:return:
"""
train, val = LabelledCollection(instances, labels).split_stratified(1-val_split)
self.classes_ = train.classes_
opt = self.trainer_hyperparams
checkpoint = self.checkpointpath
self.reset_net_params(self.vocab_size, train.n_classes)
train_generator = TorchDataset(train.instances, train.labels).asDataloader(
opt['batch_size'], shuffle=True, pad_length=opt['padding_length'], device=opt['device'])
valid_generator = TorchDataset(val.instances, val.labels).asDataloader(
opt['batch_size_test'], shuffle=False, pad_length=opt['padding_length'], device=opt['device'])
self.status = {'tr': {'loss': -1, 'acc': -1, 'f1': -1},
'va': {'loss': -1, 'acc': -1, 'f1': -1}}
self.optim = torch.optim.Adam(self.net.parameters(), lr=opt['lr'], weight_decay=opt['weight_decay'])
self.early_stop = EarlyStop(opt['patience'], lower_is_better=False)
with tqdm(range(1, opt['epochs'] + 1)) as pbar:
for epoch in pbar:
self._train_epoch(train_generator, self.status['tr'], pbar, epoch)
self._test_epoch(valid_generator, self.status['va'], pbar, epoch)
self.early_stop(self.status['va']['f1'], epoch)
if self.early_stop.IMPROVED:
torch.save(self.net.state_dict(), checkpoint)
elif self.early_stop.STOP:
print(f'training ended by patience exhasted; loading best model parameters in {checkpoint} '
f'for epoch {self.early_stop.best_epoch}')
self.net.load_state_dict(torch.load(checkpoint))
break
print('performing one training pass over the validation set...')
self._train_epoch(valid_generator, self.status['tr'], pbar, epoch=0)
print('[done]')
return self
def predict(self, instances):
"""
Predicts labels for the instances
:param instances: list of lists of indexed tokens
:return: a `numpy` array of length `n` containing the label predictions, where `n` is the number of
instances in `X`
"""
return np.argmax(self.predict_proba(instances), axis=-1)
def predict_proba(self, instances):
"""
Predicts posterior probabilities for the instances
:param X: array-like of shape `(n_samples, n_features)` instances to classify
:return: array-like of shape `(n_samples, n_classes)` with the posterior probabilities
"""
self.net.eval()
opt = self.trainer_hyperparams
with torch.no_grad():
posteriors = []
for xi in TorchDataset(instances).asDataloader(
opt['batch_size_test'], shuffle=False, pad_length=opt['padding_length'], device=opt['device']):
posteriors.append(self.net.predict_proba(xi))
return np.concatenate(posteriors)
def transform(self, instances):
"""
Returns the embeddings of the instances
:param instances: list of lists of indexed tokens
:return: array-like of shape `(n_samples, embed_size)` with the embedded instances,
where `embed_size` is defined by the classification network
"""
self.net.eval()
embeddings = []
opt = self.trainer_hyperparams
with torch.no_grad():
for xi in TorchDataset(instances).asDataloader(
opt['batch_size_test'], shuffle=False, pad_length=opt['padding_length'], device=opt['device']):
embeddings.append(self.net.document_embedding(xi).detach().cpu().numpy())
return np.concatenate(embeddings)
class TorchDataset(torch.utils.data.Dataset):
"""
Transforms labelled instances into a Torch's :class:`torch.utils.data.DataLoader` object
:param instances: list of lists of indexed tokens
:param labels: array-like of shape `(n_samples, n_classes)` with the class labels
"""
def __init__(self, instances, labels=None):
self.instances = instances
self.labels = labels
def __len__(self):
return len(self.instances)
def __getitem__(self, index):
return {'doc': self.instances[index], 'label': self.labels[index] if self.labels is not None else None}
def asDataloader(self, batch_size, shuffle, pad_length, device):
"""
Converts the labelled collection into a Torch DataLoader with dynamic padding for
the batch
:param batch_size: batch size
:param shuffle: whether or not to shuffle instances
:param pad_length: the maximum length for the list of tokens (dynamic padding is
applied, meaning that if the longest document in the batch is shorter than
`pad_length`, then the batch is padded up to its length, and not to `pad_length`.
:param device: whether to allocate tensors in cpu or in cuda
:return: a :class:`torch.utils.data.DataLoader` object
"""
def collate(batch):
data = [torch.LongTensor(item['doc'][:pad_length]) for item in batch]
data = pad_sequence(data, batch_first=True, padding_value=qp.environ['PAD_INDEX']).to(device)
targets = [item['label'] for item in batch]
if targets[0] is None:
return data
else:
targets = torch.as_tensor(targets, dtype=torch.long).to(device)
return [data, targets]
torchDataset = TorchDataset(self.instances, self.labels)
return torch.utils.data.DataLoader(torchDataset, batch_size=batch_size, shuffle=shuffle, collate_fn=collate)
class TextClassifierNet(torch.nn.Module, metaclass=ABCMeta):
"""
Abstract Text classifier (`torch.nn.Module`)
"""
@abstractmethod
def document_embedding(self, x):
"""Embeds documents (i.e., performs the forward pass up to the
next-to-last layer).
:param x: a batch of instances, typically generated by a torch's `DataLoader`
instance (see :class:`quapy.classification.neural.TorchDataset`)
:return: a torch tensor of shape `(n_samples, n_dimensions)`, where
`n_samples` is the number of documents, and `n_dimensions` is the
dimensionality of the embedding
"""
...
def forward(self, x):
"""Performs the forward pass.
:param x: a batch of instances, typically generated by a torch's `DataLoader`
instance (see :class:`quapy.classification.neural.TorchDataset`)
:return: a tensor of shape `(n_instances, n_classes)` with the decision scores
for each of the instances and classes
"""
doc_embedded = self.document_embedding(x)
return self.output(doc_embedded)
def dimensions(self):
"""Gets the number of dimensions of the embedding space
:return: integer
"""
return self.dim
def predict_proba(self, x):
"""
Predicts posterior probabilities for the instances in `x`
:param x: a torch tensor of indexed tokens with shape `(n_instances, pad_length)`
where `n_instances` is the number of instances in the batch, and `pad_length`
is length of the pad in the batch
:return: array-like of shape `(n_samples, n_classes)` with the posterior probabilities
"""
logits = self(x)
return torch.softmax(logits, dim=1).detach().cpu().numpy()
def xavier_uniform(self):
"""
Performs Xavier initialization of the network parameters
"""
for p in self.parameters():
if p.dim() > 1 and p.requires_grad:
torch.nn.init.xavier_uniform_(p)
@abstractmethod
def get_params(self):
"""
Get hyper-parameters for this estimator
:return: a dictionary with parameter names mapped to their values
"""
...
@property
def vocabulary_size(self):
"""
Return the size of the vocabulary
:return: integer
"""
...
class LSTMnet(TextClassifierNet):
"""
An implementation of :class:`quapy.classification.neural.TextClassifierNet` based on
Long Short Term Memory networks.
:param vocabulary_size: the size of the vocabulary
:param n_classes: number of target classes
:param embedding_size: the dimensionality of the word embeddings space (default 100)
:param hidden_size: the dimensionality of the hidden space (default 256)
:param repr_size: the dimensionality of the document embeddings space (default 100)
:param lstm_class_nlayers: number of LSTM layers (default 1)
:param drop_p: drop probability for dropout (default 0.5)
"""
def __init__(self, vocabulary_size, n_classes, embedding_size=100, hidden_size=256, repr_size=100, lstm_class_nlayers=1,
drop_p=0.5):
super().__init__()
self.vocabulary_size_ = vocabulary_size
self.n_classes = n_classes
self.hyperparams={
'embedding_size': embedding_size,
'hidden_size': hidden_size,
'repr_size': repr_size,
'lstm_class_nlayers': lstm_class_nlayers,
'drop_p': drop_p
}
self.word_embedding = torch.nn.Embedding(vocabulary_size, embedding_size)
self.lstm = torch.nn.LSTM(embedding_size, hidden_size, lstm_class_nlayers, dropout=drop_p, batch_first=True)
self.dropout = torch.nn.Dropout(drop_p)
self.dim = repr_size
self.doc_embedder = torch.nn.Linear(hidden_size, self.dim)
self.output = torch.nn.Linear(self.dim, n_classes)
def __init_hidden(self, set_size):
opt = self.hyperparams
var_hidden = torch.zeros(opt['lstm_class_nlayers'], set_size, opt['hidden_size'])
var_cell = torch.zeros(opt['lstm_class_nlayers'], set_size, opt['hidden_size'])
if next(self.lstm.parameters()).is_cuda:
var_hidden, var_cell = var_hidden.cuda(), var_cell.cuda()
return var_hidden, var_cell
def document_embedding(self, x):
"""Embeds documents (i.e., performs the forward pass up to the
next-to-last layer).
:param x: a batch of instances, typically generated by a torch's `DataLoader`
instance (see :class:`quapy.classification.neural.TorchDataset`)
:return: a torch tensor of shape `(n_samples, n_dimensions)`, where
`n_samples` is the number of documents, and `n_dimensions` is the
dimensionality of the embedding
"""
embedded = self.word_embedding(x)
rnn_output, rnn_hidden = self.lstm(embedded, self.__init_hidden(x.size()[0]))
abstracted = self.dropout(F.relu(rnn_hidden[0][-1]))
abstracted = self.doc_embedder(abstracted)
return abstracted
def get_params(self):
"""
Get hyper-parameters for this estimator
:return: a dictionary with parameter names mapped to their values
"""
return self.hyperparams
@property
def vocabulary_size(self):
"""
Return the size of the vocabulary
:return: integer
"""
return self.vocabulary_size_
class CNNnet(TextClassifierNet):
"""
An implementation of :class:`quapy.classification.neural.TextClassifierNet` based on
Convolutional Neural Networks.
:param vocabulary_size: the size of the vocabulary
:param n_classes: number of target classes
:param embedding_size: the dimensionality of the word embeddings space (default 100)
:param hidden_size: the dimensionality of the hidden space (default 256)
:param repr_size: the dimensionality of the document embeddings space (default 100)
:param kernel_heights: list of kernel lengths (default [3,5,7]), i.e., the number of
consecutive tokens that each kernel covers
:param stride: convolutional stride (default 1)
:param stride: convolutional pad (default 0)
:param drop_p: drop probability for dropout (default 0.5)
"""
def __init__(self, vocabulary_size, n_classes, embedding_size=100, hidden_size=256, repr_size=100,
kernel_heights=[3, 5, 7], stride=1, padding=0, drop_p=0.5):
super(CNNnet, self).__init__()
self.vocabulary_size_ = vocabulary_size
self.n_classes = n_classes
self.hyperparams={
'embedding_size': embedding_size,
'hidden_size': hidden_size,
'repr_size': repr_size,
'kernel_heights':kernel_heights,
'stride': stride,
'drop_p': drop_p
}
self.word_embedding = torch.nn.Embedding(vocabulary_size, embedding_size)
in_channels = 1
self.conv1 = nn.Conv2d(in_channels, hidden_size, (kernel_heights[0], embedding_size), stride, padding)
self.conv2 = nn.Conv2d(in_channels, hidden_size, (kernel_heights[1], embedding_size), stride, padding)
self.conv3 = nn.Conv2d(in_channels, hidden_size, (kernel_heights[2], embedding_size), stride, padding)
self.dropout = nn.Dropout(drop_p)
self.dim = repr_size
self.doc_embedder = torch.nn.Linear(len(kernel_heights) * hidden_size, self.dim)
self.output = nn.Linear(self.dim, n_classes)
def __conv_block(self, input, conv_layer):
conv_out = conv_layer(input) # conv_out.size() = (batch_size, out_channels, dim, 1)
activation = F.relu(conv_out.squeeze(3)) # activation.size() = (batch_size, out_channels, dim1)
max_out = F.max_pool1d(activation, activation.size()[2]).squeeze(2) # maxpool_out.size() = (batch_size, out_channels)
return max_out
def document_embedding(self, input):
"""Embeds documents (i.e., performs the forward pass up to the
next-to-last layer).
:param input: a batch of instances, typically generated by a torch's `DataLoader`
instance (see :class:`quapy.classification.neural.TorchDataset`)
:return: a torch tensor of shape `(n_samples, n_dimensions)`, where
`n_samples` is the number of documents, and `n_dimensions` is the
dimensionality of the embedding
"""
input = self.word_embedding(input)
input = input.unsqueeze(1) # input.size() = (batch_size, 1, num_seq, embedding_length)
max_out1 = self.__conv_block(input, self.conv1)
max_out2 = self.__conv_block(input, self.conv2)
max_out3 = self.__conv_block(input, self.conv3)
all_out = torch.cat((max_out1, max_out2, max_out3), 1) # all_out.size() = (batch_size, num_kernels*out_channels)
abstracted = self.dropout(F.relu(all_out)) # (batch_size, num_kernels*out_channels)
abstracted = self.doc_embedder(abstracted)
return abstracted
def get_params(self):
"""
Get hyper-parameters for this estimator
:return: a dictionary with parameter names mapped to their values
"""
return self.hyperparams
@property
def vocabulary_size(self):
"""
Return the size of the vocabulary
:return: integer
"""
return self.vocabulary_size_