ch14_part1.py

# coding: utf-8


import sys
from python_environment_check import check_packages
import torch
import numpy as np
import scipy.signal
from torchvision.io import read_image
import torch.nn as nn
import torchvision 
from torchvision import transforms 
from torch.utils.data import Subset
from torch.utils.data import DataLoader
import matplotlib.pyplot as plt
import os

# # Machine Learning with PyTorch and Scikit-Learn  
# # -- Code Examples

# ## Package version checks

# Add folder to path in order to load from the check_packages.py script:



sys.path.insert(0, '..')


# Check recommended package versions:





d = {
    'numpy': '1.21.2',
    'scipy': '1.7.0',
    'matplotlib': '3.4.3',
    'torch': '1.8.0',
    'torchvision': '0.9.0'
}
check_packages(d)


# # Chapter 14: Classifying Images with Deep Convolutional Neural Networks (Part 1/2)

# **Outline**
# 
# - [The building blocks of CNNs](#The-building-blocks-of-CNNs)
#   - [Understanding CNNs and feature hierarchies](#Understanding-CNNs-and-feature-hierarchies)
#   - [Performing discrete convolutions](#Performing-discrete-convolutions)
#     - [Discrete convolutions in one dimension](#Discrete-convolutions-in-one-dimension)
#     - [Padding inputs to control the size of the output feature maps](#Padding-inputs-to-control-the-size-of-the-output-feature-maps)
#     - [Determining the size of the convolution output](#Determining-the-size-of-the-convolution-output)
#     - [Performing a discrete convolution in 2D](#Performing-a-discrete-convolution-in-2D)
#   - [Subsampling layers](#Subsampling-layers)
# - [Putting everything together -- implementing a CNN](#Putting-everything-together----implementing-a-CNN)
#   - [Working with multiple input or color channels](#Working-with-multiple-input-or-color-channels)
#   - [Regularizing an NN with L2 regularization and dropout](#Regularizing-an-NN-with-L2-regularization-and-dropout)
#   - [Loss functions for classification](#Loss-functions-for-classification)
# - [Implementing a deep CNN using PyTorch](#Implementing-a-deep-CNN-using-PyTorch)
#   - [The multilayer CNN architecture](#The-multilayer-CNN-architecture)
#   - [Loading and preprocessing the data](#Loading-and-preprocessing-the-data)
#   - [Implementing a CNN using the torch.nn module](#Implementing-a-CNN-using-the-torch.nn-module)
#     - [Configuring CNN layers in PyTorch](#Configuring-CNN-layers-in-PyTorch)
#     - [Constructing a CNN in PyTorch](#Constructing-a-CNN-in-PyTorch)





# ##  The building blocks of convolutional neural networks
# 
# ### Understanding CNNs and feature hierarchies





# 
# 
# ### Performing discrete convolutions
# 
# ### Discrete convolutions in one dimension
# 
# 









# ### Padding inputs to control the size of the output feature maps
# 
# 





# ### Determining the size of the convolution output




print('PyTorch version:', torch.__version__)
print('NumPy version: ', np.__version__)




def conv1d(x, w, p=0, s=1):
    w_rot = np.array(w[::-1])
    x_padded = np.array(x)
    if p > 0:
        zero_pad = np.zeros(shape=p)
        x_padded = np.concatenate(
            [zero_pad, x_padded, zero_pad])
    res = []
    for i in range(0, int((len(x_padded) - len(w_rot))) + 1, s):
        res.append(np.sum(
            x_padded[i:i+w_rot.shape[0]] * w_rot))
    return np.array(res)


## Testing:
x = [1, 3, 2, 4, 5, 6, 1, 3]
w = [1, 0, 3, 1, 2]

print('Conv1d Implementation:',
      conv1d(x, w, p=2, s=1))

print('Numpy Results:',
      np.convolve(x, w, mode='same')) 


# ### Performing a discrete convolution in 2D

















def conv2d(X, W, p=(0, 0), s=(1, 1)):
    W_rot = np.array(W)[::-1,::-1]
    X_orig = np.array(X)
    n1 = X_orig.shape[0] + 2*p[0]
    n2 = X_orig.shape[1] + 2*p[1]
    X_padded = np.zeros(shape=(n1, n2))
    X_padded[p[0]:p[0]+X_orig.shape[0],
    p[1]:p[1]+X_orig.shape[1]] = X_orig

    res = []
    for i in range(0, int((X_padded.shape[0] - 
                           W_rot.shape[0])/s[0])+1, s[0]):
        res.append([])
        for j in range(0, int((X_padded.shape[1] - 
                               W_rot.shape[1])/s[1])+1, s[1]):
            X_sub = X_padded[i:i+W_rot.shape[0],
                             j:j+W_rot.shape[1]]
            res[-1].append(np.sum(X_sub * W_rot))
    return(np.array(res))

X = [[1, 3, 2, 4], [5, 6, 1, 3], [1, 2, 0, 2], [3, 4, 3, 2]]
W = [[1, 0, 3], [1, 2, 1], [0, 1, 1]]

print('Conv2d Implementation:\n',
    conv2d(X, W, p=(1, 1), s=(1, 1)))


print('SciPy Results:\n',
    scipy.signal.convolve2d(X, W, mode='same'))


# ## Subsampling layers





# ## Putting everything together – implementing a CNN
# 
# ### Working with multiple input or color channels
# 
# 





# **TIP: Reading an image file**



 
img = read_image('example-image.png') 
 
print('Image shape:', img.shape)
print('Number of channels:', img.shape[0])
print('Image data type:', img.dtype)
print(img[:, 100:102, 100:102])


# ## Regularizing a neural network with L2 regularization and dropout
# 
# 







loss_func = nn.BCELoss()
loss = loss_func(torch.tensor([0.9]), torch.tensor([1.0]))
l2_lambda = 0.001

conv_layer = nn.Conv2d(in_channels=3, out_channels=5, kernel_size=5)
l2_penalty = l2_lambda * sum([(p**2).sum() for p in conv_layer.parameters()])
loss_with_penalty = loss + l2_penalty

linear_layer = nn.Linear(10, 16)
l2_penalty = l2_lambda * sum([(p**2).sum() for p in linear_layer.parameters()])
loss_with_penalty = loss + l2_penalty


# ## Loss Functions for Classification
# 
#  * **`nn.BCELoss()`**
#    * `from_logits=False` 
#    * `from_logits=True`
# 
#  * **`nn.CrossEntropyLoss()`**
#    * `from_logits=False`
#    * `from_logits=True`
# 







####### Binary Cross-entropy
logits = torch.tensor([0.8])
probas = torch.sigmoid(logits)
target = torch.tensor([1.0])

bce_loss_fn = nn.BCELoss()
bce_logits_loss_fn = nn.BCEWithLogitsLoss()

print(f'BCE (w Probas): {bce_loss_fn(probas, target):.4f}')
print(f'BCE (w Logits): {bce_logits_loss_fn(logits, target):.4f}')

 
####### Categorical Cross-entropy
logits = torch.tensor([[1.5, 0.8, 2.1]])
probas = torch.softmax(logits, dim=1)
target = torch.tensor([2])

cce_loss_fn = nn.NLLLoss()
cce_logits_loss_fn = nn.CrossEntropyLoss()

print(f'CCE (w Probas): {cce_logits_loss_fn(logits, target):.4f}')
print(f'CCE (w Logits): {cce_loss_fn(torch.log(probas), target):.4f}')


# ## Implementing a deep convolutional neural network using PyTorch
# 
# ### The multilayer CNN architecture





# ### Loading and preprocessing the data



image_path = './'
transform = transforms.Compose([transforms.ToTensor()])

mnist_dataset = torchvision.datasets.MNIST(root=image_path, 
                                           train=True, 
                                           transform=transform, 
                                           download=False)

mnist_valid_dataset = Subset(mnist_dataset, torch.arange(10000)) 
mnist_train_dataset = Subset(mnist_dataset, torch.arange(10000, len(mnist_dataset)))
mnist_test_dataset = torchvision.datasets.MNIST(root=image_path, 
                                           train=False, 
                                           transform=transform, 
                                           download=False)




batch_size = 64
torch.manual_seed(1)
train_dl = DataLoader(mnist_train_dataset, batch_size, shuffle=True)
valid_dl = DataLoader(mnist_valid_dataset, batch_size, shuffle=False)


# ### Implementing a CNN using the torch.nn module
# 
# #### Configuring CNN layers in PyTorch
# 
#  * **Conv2d:** `torch.nn.Conv2d`
#    * `out_channels`
#    * `kernel_size`
#    * `stride`
#    * `padding`
#    
#    
#  * **MaxPool2d:** `torch.nn.MaxPool2d`
#    * `kernel_size`
#    * `stride`
#    * `padding`
#    
#    
#  * **Dropout** `torch.nn.Dropout`
#    * `p`

# ### Constructing a CNN in PyTorch



model = nn.Sequential()
model.add_module('conv1', nn.Conv2d(in_channels=1, out_channels=32, kernel_size=5, padding=2))
model.add_module('relu1', nn.ReLU())        
model.add_module('pool1', nn.MaxPool2d(kernel_size=2))   
model.add_module('conv2', nn.Conv2d(in_channels=32, out_channels=64, kernel_size=5, padding=2))
model.add_module('relu2', nn.ReLU())        
model.add_module('pool2', nn.MaxPool2d(kernel_size=2))      

x = torch.ones((4, 1, 28, 28))
model(x).shape




model.add_module('flatten', nn.Flatten()) 

x = torch.ones((4, 1, 28, 28))
model(x).shape




model.add_module('fc1', nn.Linear(3136, 1024)) 
model.add_module('relu3', nn.ReLU()) 
model.add_module('dropout', nn.Dropout(p=0.5)) 

model.add_module('fc2', nn.Linear(1024, 10)) 
model.add_module('softmax', nn.Softmax(dim=1)) 
 




device = torch.device("cuda:0")
# device = torch.device("cpu")

model = model.to(device) 




loss_fn = nn.CrossEntropyLoss()
optimizer = torch.optim.Adam(model.parameters(), lr=0.001)

def train(model, num_epochs, train_dl, valid_dl):
    loss_hist_train = [0] * num_epochs
    accuracy_hist_train = [0] * num_epochs
    loss_hist_valid = [0] * num_epochs
    accuracy_hist_valid = [0] * num_epochs
    for epoch in range(num_epochs):
        model.train()
        for x_batch, y_batch in train_dl:
            x_batch = x_batch.to(device) 
            y_batch = y_batch.to(device) 
            pred = model(x_batch)
            loss = loss_fn(pred, y_batch)
            loss.backward()
            optimizer.step()
            optimizer.zero_grad()
            loss_hist_train[epoch] += loss.item()*y_batch.size(0)
            is_correct = (torch.argmax(pred, dim=1) == y_batch).float()
            accuracy_hist_train[epoch] += is_correct.sum().cpu()

        loss_hist_train[epoch] /= len(train_dl.dataset)
        accuracy_hist_train[epoch] /= len(train_dl.dataset)
        
        model.eval()
        with torch.no_grad():
            for x_batch, y_batch in valid_dl:
                x_batch = x_batch.to(device) 
                y_batch = y_batch.to(device) 
                pred = model(x_batch)
                loss = loss_fn(pred, y_batch)
                loss_hist_valid[epoch] += loss.item()*y_batch.size(0) 
                is_correct = (torch.argmax(pred, dim=1) == y_batch).float() 
                accuracy_hist_valid[epoch] += is_correct.sum().cpu()

        loss_hist_valid[epoch] /= len(valid_dl.dataset)
        accuracy_hist_valid[epoch] /= len(valid_dl.dataset)
        
        print(f'Epoch {epoch+1} accuracy: {accuracy_hist_train[epoch]:.4f} val_accuracy: {accuracy_hist_valid[epoch]:.4f}')
    return loss_hist_train, loss_hist_valid, accuracy_hist_train, accuracy_hist_valid

torch.manual_seed(1)
num_epochs = 20
hist = train(model, num_epochs, train_dl, valid_dl)




x_arr = np.arange(len(hist[0])) + 1

fig = plt.figure(figsize=(12, 4))
ax = fig.add_subplot(1, 2, 1)
ax.plot(x_arr, hist[0], '-o', label='Train loss')
ax.plot(x_arr, hist[1], '--<', label='Validation loss')
ax.set_xlabel('Epoch', size=15)
ax.set_ylabel('Loss', size=15)
ax.legend(fontsize=15)
ax = fig.add_subplot(1, 2, 2)
ax.plot(x_arr, hist[2], '-o', label='Train acc.')
ax.plot(x_arr, hist[3], '--<', label='Validation acc.')
ax.legend(fontsize=15)
ax.set_xlabel('Epoch', size=15)
ax.set_ylabel('Accuracy', size=15)

plt.show()




torch.cuda.synchronize()
model_cpu = model.cpu()
pred = model(mnist_test_dataset.data.unsqueeze(1) / 255.)
is_correct = (torch.argmax(pred, dim=1) == mnist_test_dataset.targets).float()
print(f'Test accuracy: {is_correct.mean():.4f}') 
 




fig = plt.figure(figsize=(12, 4))
for i in range(12):
    ax = fig.add_subplot(2, 6, i+1)
    ax.set_xticks([]); ax.set_yticks([])
    img = mnist_test_dataset[i][0][0, :, :]
    pred = model(img.unsqueeze(0).unsqueeze(1))
    y_pred = torch.argmax(pred)
    ax.imshow(img, cmap='gray_r')
    ax.text(0.9, 0.1, y_pred.item(), 
            size=15, color='blue',
            horizontalalignment='center',
            verticalalignment='center', 
            transform=ax.transAxes)
    
plt.show()





if not os.path.exists('models'):
    os.mkdir('models')

path = 'models/mnist-cnn.ph'
torch.save(model, path)
 


# ----
# 
# Readers may ignore the next cell.