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Autoencoders in Action

Explore autoencoders by training a neural network to compress and reconstruct MNIST images using PyTorch. Understand how the encoder reduces input dimensions while the decoder rebuilds images. Learn to evaluate reconstruction quality and the impact of different compression levels, gaining insights into dimensionality reduction and nonlinear data representation.

We’ll explore the fascinating world of autoencoders by applying them to the MNIST dataset. Autoencoders are powerful models that consist of an encoder and a decoder. The encoder compresses input images while the decoder reconstructs them. Our focus will be on image reconstruction.

Target: Using PyTorch, we’ll train an autoencoder model to reduce 784 input values to a lower-dimensional representation as low as possible.

By doing so, we aim to investigate whether this condensed representation preserves the same level of informativeness as the original features.

An example of image reconstruction
An example of image reconstruction

Loading and preprocessing the data

To begin, let’s import the necessary libraries for performing image-related tasks and implementing neural networks using PyTorch. We’ll use torch for tensorA tensor is a multi-dimensional array that can represent scalars, vectors, matrices, or higher-dimensional data. It’s the fundamental data structure in PyTorch for storing and processing inputs, weights, and outputs in deep learning. operations and network functionalities, torch.nn for building networks, torch.optim for optimization algorithms, torchvision for datasets and model architectures, and torchvision.transforms for image transformations.

Python 3.5
import torch
import torch.nn as nn
import torch.optim as optim
import torchvision
import torchvision.transforms as transforms

To load the MNIST dataset, we can utilize the torchvision.datasets.MNIST() function. This function allows us to load the dataset while specifying the root directory where the data will be stored. To load the training set, we set the parameter train=True, and for the testing set, we set train=False.

Once the dataset is loaded, we assign the MNIST image data to variables named x_train and x_test, and the corresponding labels to variables named y_train and y_test. To ensure compatibility with our model, we convert the image data to float type. Additionally, to normalize the pixel values ...

Python 3.5
# Load MNIST training and test datasets
mnist_train = torchvision.datasets.MNIST(root='./data', train=True, download=True, )
mnist_test = torchvision.datasets.MNIST(root='./data', train=False, download=True)
# Extract images and labels
x_train = mnist_train.data
y_train = mnist_train.targets
x_test = mnist_test.data
y_test = mnist_test.targets
# Normalize images to [0, 1]
x_train = x_train.float()/255.0
x_test = x_test.float()/255.0

As ...