MNIST dataset overfitting - pytorch

I am working with the MNIST dataset and I have created the following network. I want to overfit the training data and I think I am doing that here. My training loss is lower than my validation loss. This is the code that I have come up with. Please look at it and let me know if I am overfitting the training data, if I am not then how do I go about it?
class NN(nn.Module):
def __init__(self):
super().__init__()
self.layers = nn.Sequential(
nn.Flatten(),
nn.Linear(784,4096),
nn.ReLU(),
nn.Linear(4096,2048),
nn.ReLU(),
nn.Linear(2048,1024),
nn.ReLU(),
nn.Linear(1024,512),
nn.ReLU(),
nn.Linear(512,256),
nn.ReLU(),
nn.Linear(256,128),
nn.ReLU(),
nn.Linear(128,64),
nn.ReLU(),
nn.Linear(64,32),
nn.ReLU(),
nn.Linear(32,16),
nn.ReLU(),
nn.Linear(16,10))
def forward(self,x):
return self.layers(x)
def accuracy_and_loss(model, loss_function, dataloader):
total_correct = 0
total_loss = 0
total_examples = 0
n_batches = 0
with torch.no_grad():
for data in testloader:
images, labels = data
outputs = model(images)
batch_loss = loss_function(outputs,labels)
n_batches += 1
total_loss += batch_loss.item()
_, predicted = torch.max(outputs, dim=1)
total_examples += labels.size(0)
total_correct += (predicted == labels).sum().item()
accuracy = total_correct / total_examples
mean_loss = total_loss / n_batches
return (accuracy, mean_loss)
def define_and_train(model,dataset_training, dataset_test):
trainloader = torch.utils.data.DataLoader( small_trainset, batch_size=500, shuffle=True)
testloader = torch.utils.data.DataLoader( dataset_test, batch_size=500, shuffle=True)
values = [1e-8,1e-7,1e-6,1e-5]
model = NN()
for params in values:
optimizer = torch.optim.Adam(model.parameters(), lr=0.001, weight_decay = 1e-7)
train_acc = []
val_acc = []
train_loss = []
val_loss = []
for epoch in range(100):
total_loss = 0
total_correct = 0
total_examples = 0
n_mini_batches = 0
for i,mini_batch in enumerate(trainloader,0):
images,labels = mini_batch
optimizer.zero_grad()
outputs = model(images)
loss = loss_function(outputs,labels)
loss.backward()
optimizer.step()
n_mini_batches += 1
total_loss += loss.item()
_, predicted = torch.max(outputs, dim=1)
total_examples += labels.size(0)
total_correct += (predicted == labels).sum().item()
epoch_training_accuracy = total_correct / total_examples
epoch_training_loss = total_loss / n_mini_batches
epoch_val_accuracy, epoch_val_loss = accuracy_and_loss( model, loss_function, testloader )
print('Params %f Epoch %d loss: %.3f acc: %.3f val_loss: %.3f val_acc: %.3f'
%(params, epoch+1, epoch_training_loss, epoch_training_accuracy, epoch_val_loss, epoch_val_accuracy))
train_loss.append( epoch_training_loss )
train_acc.append( epoch_training_accuracy )
val_loss.append( epoch_val_loss )
val_acc.append( epoch_val_accuracy )
history = { 'train_loss': train_loss,
'train_acc': train_acc,
'val_loss': val_loss,
'val_acc': val_acc }
return ( history, model )
history1, net1 = define_and_train(model,dataset_training,dataset_test)
I am trying to overfit the training data so that later i can apply regularization and then reduce the overfitting which will give me a better understanding of the process

Although I won't attempt to provide a rigorous definition, the term "overfit" typically means that the training loss continues to decrease whereas the validation loss stays stagnant at a position higher than the training loss, or continues to increase with more iterations.
Therefore, it is difficult to know whether your network is overfitting solely based on your code alone. Since dense, fully-connected networks tend to overfit easily in the absence of dropout layers or other regularizers, my hunch would be that your network is indeed overfitting according to your intention. However, we would have to see your tensorboard logs or loss plot to determine whether the model is overfitting.
If you want to overfit your network to the dataset, I suggest that you construct a much larger model with more hidden layers. Overfitting occurs when the dataset is "too easy" for the model and it starts to remember the training set itself without learning generalizable patterns that can be applied to the validation set.

Related

Unable to assign all tensors to the GPU

I am trying to predict the outcome of a football fixture (using backpropagation) across 3 classes: home team wins, draw or away team wins; they are encoded as 0, 1, and 2, respectively.
Features: home_team, away_team, home_score, away_score, home_adv, match_imp
Target: outcome_final
Training, validation and test tensors:
X_train: torch.Size([25365, 554])
y_train: torch.Size([25365])
X_test: torch.Size([5436, 554])
y_test: torch.Size([5436])
X_val: torch.Size([5436, 554])
y_val: torch.Size([5436])
Network architecture:
Net(
(fc1): Linear(in_features=555, out_features=100, bias=True)
(fc2): Linear(in_features=100, out_features=3, bias=True)
(dropout): Dropout(p=0.2, inplace=False)
)
Weights and biases are generated at first:
fc1.weight: torch.Size([100, 554])
fc1.bias: torch.Size([100])
fc2.weight: torch.Size([3, 100])
fc2.bias: torch.Size([3])
ReLU activation function is used for the hidden layer, and Softmax activation function is used for the output layer.
The following code returns the error below.
# Creating the class for the neural network
class Net(nn.Module):
def __init__(self):
super(Net, self).__init__()
self.fc1 = nn.Linear(554, 100)
self.fc2 = nn.Linear(100, 3)
self.dropout = nn.Dropout(p = 0.2)
def forward(self, x):
x = F.relu(self.fc1(x))
x = self.dropout(x)
x = F.softmax(self.fc2(x), dim = 1)
return x
# Initializing model
model = Net().to(device)
X_train.to(device)
y_train.to(device)
X_val.to(device)
y_val.to(device)
# Initializing weights and biases
model.fc1.weight.data.normal_(0, 0.01)
model.fc1.bias.data.normal_(0, 0.01)
model.fc2.weight.data.normal_(0, 0.01)
model.fc2.bias.data.normal_(0, 0.01)
# TRAIN the model
def train_model(model, X_train, y_train, X_val, y_val, epochs = 10, learning_rate = 0.003):
# Loss function and optimizer
criterion = nn.CrossEntropyLoss()
optimizer = optim.Adam(model.parameters(), lr = learning_rate)
# Losses and accuracies
train_losses = []
val_losses = []
train_accs = []
val_accs = []
# Training happens here
for epoch in range(epochs):
# Shuffling data
permutation = torch.randperm(X_train.size()[0]).to(device)
X_train = X_train[permutation]
y_train = y_train[permutation]
# Creating batches
batch_size = 5
n_batches = X_train.size()[0] // batch_size
for i in range(n_batches):
# Zeroing gradients
optimizer.zero_grad()
# Forward pass
output = model(X_train[i * batch_size : (i + 1) * batch_size])
loss = criterion(output, y_train[i * batch_size : (i + 1) * batch_size].long())
# Backward pass
loss.backward()
# Updating weights and biases
optimizer.step()
# Sending to CPU
model.to('cpu')
# Training loss and accuracy
train_loss = criterion(model(X_train), y_train.long())
train_losses.append(train_loss)
train_acc = accuracy_score(y_train, torch.argmax(model(X_train), dim = 1))
train_accs.append(train_acc)
print('Epoch: ', epoch + 1, 'Training Loss: ', train_loss, 'Training Accuracy: ', train_acc)
# Validation loss and accuracy
val_loss = criterion(model(X_val), y_val.long())
val_losses.append(val_loss)
val_acc = accuracy_score(y_val, torch.argmax(model(X_val), dim = 1))
val_accs.append(val_acc)
print('Epoch: ', epoch + 1, 'Validation Loss: ', val_loss, 'Validation Accuracy: ', val_acc)
# Sending back to GPU
model.to(device)
X_train.to(device)
y_train.to(device)
X_val.to(device)
y_val.to(device)
return train_losses, val_losses, train_accs, val_accs
# Let's train the model
model = Net().to(device)
train_losses, val_losses, train_accs, val_accs = train_model(model, X_train, y_train, X_val, y_val)
ERROR:
RuntimeError: Expected all tensors to be on the same device, but found at least two devices, cpu and cuda:0! (when checking argument for argument mat1 in method wrapper_addmm)
I have tried ensuring all training and validation sets are converted as tensors and sent to the GPU. Yet, I am still getting this error.
Am I missing something here? Thanks in advance.

PyTorch text classification model not improving

I am training a simple LSTM model for binary text classification. Here is the model class:
class LSTM(nn.Module):
def __init__(self, vocabulary_size, embeddings_size, num_classes):
super(LSTM, self).__init__()
self.vocabulary_size = vocabulary_size
self.embeddings_size = embeddings_size
self.embedding = nn.Embedding(num_embeddings=vocabulary_size,
embedding_dim=embeddings_size,
padding_idx=0)
self.lstm = nn.LSTM(input_size=embeddings_size,
hidden_size=128,
num_layers=1,
batch_first=True)
self.fc = nn.Linear(in_features=128,
out_features=num_classes)
def forward(self, x):
out = self.embedding(x)
out, _ = self.lstm(out)
out = out[:, -1]
out = self.fc(out)
out = torch.sigmoid(out)
return out
I am using BCELoss and Adam optimizer created with the following code:
criterion = nn.BCELoss()
optimizer = Adam(model.parameters(), lr=learning_rate)
This is the training loop that I am using:
train_steps = len(train_data_loader)
for epoch in range(epochs):
train_loss = 0
model.train()
for i, (sequences, labels) in enumerate(train_data_loader):
optimizer.zero_grad()
sequences = sequences.to(device)
labels = labels.to(device)
outputs = model(sequences)
loss = criterion(outputs, labels)
train_loss += loss.item()
loss.backward()
optimizer.step()
print(f'Epoch {epoch+1}/{epochs}, Train Loss: {train_loss / train_steps:.4f}')
I have experimented with different datasets, number of epochs, learning rate, batch size. However, the model does not seem to learn - the loss is always around 0.7 and only the 0 class is predicted.
Does anyone know what the issue could be?

Bigger batch size improves training by too much

I am writing a classifier that takes a surname and predicts a language it belongs to. I found that small batch sizes (256 and less) perform poorly compared to big batch sizes (2048 and more). Could someone give me some insight on why this is happening and how to fix it? Thank you.
Training code:
def indices_to_packed(names, input_size):
names = [F.one_hot(item, input_size).float() for item in names]
names_packed = pack_sequence(names, enforce_sorted=False)
return names_packed
def infer(model, data, labels, lengths, device):
data_packed = indices_to_packed(data, model.rnn.input_size)
data_packed, labels, lengths = data_packed.to(device), labels.to(device), lengths.to(device)
preds = model(data_packed, lengths)
loss = loss_fn(preds, labels)
return loss, preds
results = {}
epochs = 100
for BATCH_SIZE in [4096, 2048, 256]:
train_loader = data.DataLoader(train_data, BATCH_SIZE, sampler=train_sampler, collate_fn=partial(my_collate, input_size=input_size, output_size=output_size))
val_loader = data.DataLoader(val_data, BATCH_SIZE, sampler=val_sampler, collate_fn=partial(my_collate, input_size=input_size, output_size=output_size))
model = LSTM(input_size, HIDDEN_SIZE, NUM_LAYERS, DROPOUT, output_size)
optimizer = torch.optim.Adam(model.parameters())
model.to(device)
train_losses = []
val_losses = []
cur_losses = {}
duration = 0
for epoch in range(epochs):
start = time.time()
train_loss = 0
model.train()
# Using PackedSequence
for names, langs, lengths in train_loader:
optimizer.zero_grad()
loss, _ = infer(model, names, langs, lengths, device)
loss.backward()
optimizer.step()
train_loss += loss
train_loss /= len(train_data)
train_losses.append(train_loss.cpu().detach().numpy())
model.eval()
val_loss = 0
with torch.no_grad():
for names, langs, lengths in val_loader:
loss, _ = infer(model, names, langs, lengths, device)
val_loss += loss
val_loss /= len(val_data)
val_losses.append(val_loss.cpu().detach().numpy())
cur_duration = time.time() - start
duration += cur_duration
log_line = (f"BATCH_SIZE: {BATCH_SIZE} epoch: {epoch} train loss: "
f"{train_loss:.5f} val loss: {val_loss:.5f}")
print(log_line)
cur_losses["train_losses"] = train_losses
cur_losses["val_losses"] = val_losses
results[BATCH_SIZE] = {"losses" : cur_losses, "duration" : duration, "model": model}
Model:
class LSTM(nn.Module):
def __init__(self, input_size, hidden_size, num_layers, dropout, output_size):
super().__init__()
self.rnn = nn.LSTM(input_size, hidden_size, num_layers, dropout=DROPOUT)
self.linear = nn.Linear(hidden_size, output_size)
self.softmax = nn.LogSoftmax(dim=1)
def forward(self, x, lengths):
lstm_out, _ = self.rnn(x)
# https://discuss.pytorch.org/t/get-each-sequences-last-item-from-packed-sequence/41118/7
sum_batch_sizes = torch.cat((
torch.zeros(2, dtype=torch.int64),
torch.cumsum(lstm_out.batch_sizes, 0)
))
sorted_lengths = lengths[lstm_out.sorted_indices]
last_seq_idxs = sum_batch_sizes[sorted_lengths] + torch.arange(lengths.size(0))
last_seq_items = lstm_out.data[last_seq_idxs]
lstm_last_out = last_seq_items[lstm_out.unsorted_indices]
linear_out = self.linear(lstm_last_out)
softmax_out = self.softmax(linear_out)
return softmax_out
Losses with different batch sizes:
It looks like there issue is how the loss is calculated.
train_loss += loss line accumulates the loss. When batch size is higher, there will be fewer steps to do. The code normalizes this by dividing by the length of train data, train_loss /= len(train_data), but should probably take into account the batch size: train_loss /= (len(train_data) / BATCH_SIZE).
The same for validation loss, but the effect is different probably because of smaller data size compared to training data.

Almost non-existent training accuracy and low test accuracy

I am really new to Machine Learning and I am not so well versed in coding in general. However there is need to look through the customers feedback at our store, that average quite a lot each year, yet we cannot tell % of positive, negative and neutral.
Currently I am trying to train a Bert Model to do simple multi labeled sentiment analysis. The input is our store's customers feedback. The customers feedback is not always so clearly defined since customers do tend to tell long and long about their experience and their sentiment is not always so clear. However we managed to get positive, negative and neutral, each set 2247 samples.
But when I try to train it the training accuracy is around 0.4% which is super low. Validation score is around 60%. F1-score is around 60% for each of the label. I wonder what can be done to improve this training accuracy. I have been stuck for a while. Please take a look at my codes and help me out with this.
I have tried changing learning rate (tried all learning rate Bert suggested and 1e-5),changing Max LEN, changing amount of EPOCH, changing drop out rate (0.1, 0.2, 0.3, 0.4, 0.5), but so far nothing yielded results.
#read dataset
df = pd.read_csv("data.csv",header=None, names=['content', 'sentiment'], sep='\;', lineterminator='\r',encoding = "ISO-8859-1",engine="python")
from sklearn.utils import shuffle
df = shuffle(df)
df['sentiment'] = df['sentiment'].replace(to_replace = [-1, 0, 1], value = [0, 1, 2])
df.head()
#Load pretrained FinBert model and get bert tokenizer from it
PRE_TRAINED_MODEL_NAME = 'TurkuNLP/bert-base-finnish-cased-v1'
tokenizer = BertTokenizer.from_pretrained(PRE_TRAINED_MODEL_NAME)
#Choose sequence Length
token_lens = []
for txt in df.content:
tokens = tokenizer.encode(txt, max_length=512)
token_lens.append(len(tokens))
sns.distplot(token_lens)
plt.xlim([0, 256]);
plt.xlabel('Token count');
MAX_LEN = 260
#Make a PyTorch dataset
class FIDataset(Dataset):
def __init__(self, texts, targets, tokenizer, max_len):
self.texts = texts
self.targets = targets
self.tokenizer = tokenizer
self.max_len = max_len
def __len__(self):
return len(self.texts)
def __getitem__(self, item):
text = str(self.texts[item])
target = self.targets[item]
encoding = self.tokenizer.encode_plus(
text,
add_special_tokens=True,
max_length=self.max_len,
return_token_type_ids=False,
pad_to_max_length=True,
return_attention_mask=True,
return_tensors='pt',
)
return {
'text': text,
'input_ids': encoding['input_ids'].flatten(),
'attention_mask': encoding['attention_mask'].flatten(),
'targets': torch.tensor(target, dtype=torch.long)
}
#split test and train
df_train, df_test = train_test_split(
df,
test_size=0.1,
random_state=RANDOM_SEED
)
df_val, df_test = train_test_split(
df_test,
test_size=0.5,
random_state=RANDOM_SEED
)
df_train.shape, df_val.shape, df_test.shape
#data loader function
def create_data_loader(df, tokenizer, max_len, batch_size):
ds = FIDataset(
texts=df.content.to_numpy(),
targets=df.sentiment.to_numpy(),
tokenizer=tokenizer,
max_len=max_len
)
return DataLoader(
ds,
batch_size=batch_size,
num_workers=4
)
#Load data into train, test, val
BATCH_SIZE = 16
train_data_loader = create_data_loader(df_train, tokenizer, MAX_LEN, BATCH_SIZE)
val_data_loader = create_data_loader(df_val, tokenizer, MAX_LEN, BATCH_SIZE)
test_data_loader = create_data_loader(df_test, tokenizer, MAX_LEN, BATCH_SIZE)
# Sentiment Classifier based on Bert model just loaded
class SentimentClassifier(nn.Module):
def __init__(self, n_classes):
super(SentimentClassifier, self).__init__()
self.bert = BertModel.from_pretrained(PRE_TRAINED_MODEL_NAME)
self.drop = nn.Dropout(p=0.1)
self.out = nn.Linear(self.bert.config.hidden_size, n_classes)
def forward(self, input_ids, attention_mask):
returned = self.bert(
input_ids=input_ids,
attention_mask=attention_mask
)
pooled_output = returned["pooler_output"]
output = self.drop(pooled_output)
return self.out(output)
#Create a Classifier instance and move to GPU
model = SentimentClassifier(3)
model = model.to(device)
#Optimize with AdamW
EPOCHS = 5
optimizer = AdamW(model.parameters(), lr= 2e-5, correct_bias=False)
total_steps = len(train_data_loader) * EPOCHS
scheduler = get_linear_schedule_with_warmup(
optimizer,
num_warmup_steps=0,
num_training_steps=total_steps
)
loss_fn = nn.CrossEntropyLoss().to(device)
#Train each Epoch function
def train_epoch(
model,
data_loader,
loss_fn,
optimizer,
device,
scheduler,
n_examples
):
model = model.train()
losses = []
correct_predictions = 0
for d in data_loader:
input_ids = d["input_ids"].to(device)
attention_mask = d["attention_mask"].to(device)
targets = d["targets"].to(device)
outputs = model(
input_ids=input_ids,
attention_mask=attention_mask
)
_, preds = torch.max(outputs, dim=1)
loss = loss_fn(outputs, targets)
correct_predictions += torch.sum(preds == targets)
losses.append(loss.item())
loss.backward()
nn.utils.clip_grad_norm_(model.parameters(), max_norm=1.0)
optimizer.step()
scheduler.step()
optimizer.zero_grad()
return correct_predictions.double() / n_examples, np.mean(losses)
#Eval model function
def eval_model(model, data_loader, loss_fn, device, n_examples):
model = model.eval()
losses = []
correct_predictions = 0
with torch.no_grad():
torch.cuda.empty_cache()
for d in data_loader:
input_ids = d["input_ids"].to(device)
attention_mask = d["attention_mask"].to(device)
targets = d["targets"].to(device)
outputs = model(
input_ids=input_ids,
attention_mask=attention_mask
)
_, preds = torch.max(outputs, dim=1)
loss = loss_fn(outputs, targets)
correct_predictions += torch.sum(preds == targets)
losses.append(loss.item())
return correct_predictions.double() / n_examples, np.mean(losses)
#training loop through each epochs
import torch
torch.cuda.empty_cache()
history = defaultdict(list)
best_accuracy = 0
if __name__ == '__main__':
for epoch in range(EPOCHS):
print(f'Epoch {epoch + 1}/{EPOCHS}')
print('-' * 10)
train_acc, train_loss = train_epoch(
model,
train_data_loader,
loss_fn,
optimizer,
device,
scheduler,
len(df_train)
)
print(f'Train loss {train_loss} accuracy {train_acc}')
val_acc, val_loss = eval_model(
model,
val_data_loader,
loss_fn,
device,
len(df_val)
)
print(f'Val loss {val_loss} accuracy {val_acc}')
print()
history['train_acc'].append(train_acc)
history['train_loss'].append(train_loss)
history['val_acc'].append(val_acc)
history['val_loss'].append(val_loss)
if val_acc > best_accuracy:
torch.save(model.state_dict(), 'best_model_state.bin')
best_accuracy = val_acc
-- Edit: I have printed out preds and targets as well as train and val accuracy
Here _, preds = torch.max(outputs, dim=1), you probably want argmax, not max?
Print out preds and targets to better see what's going on.
Edit after preds and targets printed out. For epochs 4 and 5, preds matches targets exactly, so train accuracy should be 1. I think the issue is that the accuracy is divided by n_examples, which is a number of examples in the whole train dataset, while it should be divided by the number of examples in the epoch.

how to add BatchNormalization with SWA:stochastic weights average?

I am a beginner in Deepleaning and Pytorch.
I don't understand how to use BatchNormalization in using SWA.
pytorch.org says in https://pytorch.org/blog/stochastic-weight-averaging-in-pytorch/:
Note that the SWA averages of the weights are never used to make
predictions during training, and so the batch normalization layers do
not have the activation statistics computed after you reset the
weights of your model with opt.swap_swa_sgd()
This means it's suitable for adding BatchNormalization layer after using SWA?
# it means, in my idea
#for example
opt = torchcontrib.optim.SWA(base_opt)
for i in range(100):
opt.zero_grad()
loss_fn(model(input), target).backward()
opt.step()
if i > 10 and i % 5 == 0:
opt.update_swa()
opt.swap_swa_sgd()
#save model once
torch.save(model,"swa_model.pt")
#model_load
saved_model=torch.load("swa_model.pt")
#it means adding BatchNormalization layer??
model2=saved_model
model2.add_module("Batch1",nn.BatchNorm1d(10))
# decay learning_rate more
learning_rate=0.005
optimizer = torch.optim.SGD(model2.parameters(), lr=learning_rate)
# train model again
for epoch in range(num_epochs):
loss = train(train_loader)
val_loss, val_acc = valid(test_loader)
I appreciate your replying.
following your advise,
I try to make example model adding optimizer.bn_update()
# add optimizer.bn_update() to model
criterion = nn.CrossEntropyLoss()
learning_rate=0.01
base_opt = torch.optim.SGD(model.parameters(), lr=0.1)
optimizer = SWA(base_opt, swa_start=10, swa_freq=5, swa_lr=0.05)
def train(train_loader):
#mode:train
model.train()
running_loss = 0
for batch_idx, (images, labels) in enumerate(train_loader):
optimizer.zero_grad()
outputs = model(images)
#loss
loss = criterion(outputs, labels)
running_loss += loss.item()
loss.backward()
optimizer.step()
optimizer.swap_swa_sgd()
train_loss = running_loss / len(train_loader)
return train_loss
def valid(test_loader):
model.eval()
running_loss = 0
correct = 0
total = 0
#torch.no_grad
with torch.no_grad():
for batch_idx, (images, labels) in enumerate(test_loader):
outputs = model(images)
loss = criterion(outputs, labels)
running_loss += loss.item()
_, predicted = torch.max(outputs, 1)
correct += (predicted == labels).sum().item()
total += labels.size(0)
val_loss = running_loss / len(test_loader)
val_acc = float(correct) / total
return val_loss, val_acc
num_epochs=30
loss_list = []
val_loss_list = []
val_acc_list = []
for epoch in range(num_epochs):
loss = train(train_loader)
val_loss, val_acc = valid(test_loader)
optimizer.bn_update(train_loader, model)
print('epoch %d, loss: %.4f val_loss: %.4f val_acc: %.4f'
% (epoch, loss, val_loss, val_acc))
# logging
loss_list.append(loss)
val_loss_list.append(val_loss)
val_acc_list.append(val_acc)
# optimizer.bn_updata()
optimizer.bn_update(train_loader, model)
# go on evaluating model,,,
What the documentation is telling you is that since SWA computes averages of weights but those weights aren't used for prediction during training the batch normalization layers won't see those weights. This means they haven't computed the respective statistics for them (as they were never able to) which is important because the weights are used during actual prediction (i.e. not during training).
This means, they assume you have batch normalization layers in your model and want to train it using SWA. This is (more or less) not straight-forward due to the reasons above.
One approach is given as follows:
To compute the activation statistics you can just make a forward pass on your training data using the SWA model once the training is finished.
Or you can use their helper class:
In the SWA class we provide a helper function opt.bn_update(train_loader, model). It updates the activation statistics for every batch normalization layer in the model by making a forward pass on the train_loader data loader. You only need to call this function once in the end of training.
In case you are using Pytorch's DataLoader class you can simply supply the model (after training) and the training loader to the bn_update function which updates all batch normalization statistics for you. You only need to call this function once in the end of training.
Steps to proceed:
Train your model that includes batch normalization layers using SWA
After your model has finished training, call opt.bn_update(train_loader, model) using your training data and providing your trained model
I tried to compare before and after using optimizer.bn_update() in Mnist Data.
as follows:
# using Mnist Data
X_train = X_train.reshape(60000, 784)
X_test = X_test.reshape(10000, 784)
X_train = X_train.astype('float32')
X_test = X_test.astype('float32')
X_train /= 255
X_test /= 255
# to compare Test Data Accuracy
X_train_=X_train[0:50000]
y_train_=y_train[0:50000]
# to validate for test data
X_train_ToCompare=X_train[50000:60000]
y_train_ToCompare=y_train[50000:60000]
print(X_train_.shape)
print(y_train_.shape)
print(X_train_ToCompare.shape)
print(y_train_ToCompare.shape)
#(50000, 784)
#(50000,)
#(10000, 784)
#(10000,)
# like keras,simple MLP model
from torch import nn
model = nn.Sequential()
model.add_module('fc1', nn.Linear(784, 1000))
model.add_module('relu1', nn.ReLU())
model.add_module('fc2', nn.Linear(1000, 1000))
model.add_module('relu2', nn.ReLU())
model.add_module('fc3', nn.Linear(1000, 10))
print(model)
# using GPU
model.cuda()
criterion = nn.CrossEntropyLoss()
learning_rate=0.01
base_opt = torch.optim.SGD(model.parameters(), lr=0.1)
optimizer = SWA(base_opt, swa_start=10, swa_freq=5, swa_lr=0.05)
def train(train_loader):
model.train()
running_loss = 0
for batch_idx, (images, labels) in enumerate(train_loader):
optimizer.zero_grad()
outputs = model(images)
loss = criterion(outputs, labels)
running_loss += loss.item()
loss.backward()
optimizer.step()
optimizer.swap_swa_sgd()
train_loss = running_loss / len(train_loader)
return train_loss
def valid(test_loader):
model.eval()
running_loss = 0
correct = 0
total = 0
with torch.no_grad():
for batch_idx, (images, labels) in enumerate(test_loader):
outputs = model(images)
loss = criterion(outputs, labels)
running_loss += loss.item()
_, predicted = torch.max(outputs, 1)
correct += (predicted == labels).sum().item()
total += labels.size(0)
val_loss = running_loss / len(test_loader)
val_acc = float(correct) / total
return val_loss, val_acc
num_epochs=30
loss_list = []
val_loss_list = []
val_acc_list = []
for epoch in range(num_epochs):
loss = train(train_loader)
val_loss, val_acc = valid(test_loader)
optimizer.bn_update(train_loader, model)
print('epoch %d, loss: %.4f val_loss: %.4f val_acc: %.4f'
% (epoch, loss, val_loss, val_acc))
# logging
loss_list.append(loss)
val_loss_list.append(val_loss)
val_acc_list.append(val_acc)
# output:
# epoch 0, loss: 0.7832 val_loss: 0.5381 val_acc: 0.8866
# ...
# epoch 29, loss: 0.0502 val_loss: 0.0758 val_acc: 0.9772
#evaluate model
# attempt to evaluate model before optimizer.bn_update()
# using X_train_toCompare for test data
model.eval()
predicted_list=[]
for i in range(len(X_train_ToCompare)):
temp_predicted=model(torch.cuda.FloatTensor(X_train_ToCompare[i]))
_,y_predicted=torch.max(temp_predicte,0)
predicted_list.append(int(y_predicted))
sum(predicted_list==y_train_ToCompare)
# test accuracy 9757/10000
#after using:optimizer.bn_update
model.train()
optimizer.bn_update(train_loader, model)
# evaluate model
model.eval()
predicted_list_afterBatchNorm=[]
for i in range(len(X_train_ToCompare)):
temp_predicted=model(torch.cuda.FloatTensor(X_train_ToCompare[i]))
_,y_predicted=torch.max(temp_predicted,0)
predicted_list_afterBatchNorm.append(int(y_predicted))
sum(predicted_list_withNorm==y_train_ToCompare)
# test accuracy 9778/10000
I don't know if this way is correct to validate...
Using optimizer.bn_update() method, I confirm test accuracy is improved ofen.
but some test accuracy is descended:I think this is because of
simple MLP model and learning epochs are not enough.
there is need to try test more.
thank you for reply.

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