How do I load the CelebA dataset on Google Colab, using torch vision, without running out of memory?
I am following a tutorial on DCGAN. Whenever I try to load the CelebA dataset, torchvision uses up all my run-time's memory(12GB) and the runtime crashes. Am looking for ways on how I can load and apply transformations to the dataset without hogging my run-time's resources.
To Reproduce
Here is the part of the code that is causing issues.
# Root directory for the dataset
data_root = 'data/celeba'
# Spatial size of training images, images are resized to this size.
image_size = 64

celeba_data = datasets.CelebA(data_root,
                              download=True,
                              transform=transforms.Compose([
                                  transforms.Resize(image_size),
                                  transforms.CenterCrop(image_size),
                                  transforms.ToTensor(),
                                  transforms.Normalize(mean=[0.5, 0.5, 0.5],
                                                       std=[0.5, 0.5, 0.5])
                              ]))

The full notebook can be found here
Environment

PyTorch version: 1.7.1+cu101

Is debug build: False

CUDA used to build PyTorch: 10.1

ROCM used to build PyTorch: N/A

OS: Ubuntu 18.04.5 LTS (x86_64)

GCC version: (Ubuntu 7.5.0-3ubuntu1~18.04) 7.5.0

Clang version: 6.0.0-1ubuntu2 (tags/RELEASE_600/final)

CMake version: version 3.12.0

Python version: 3.6 (64-bit runtime)

Is CUDA available: True

CUDA runtime version: 10.1.243

GPU models and configuration: GPU 0: Tesla T4

Nvidia driver version: 418.67

cuDNN version: /usr/lib/x86_64-linux-gnu/libcudnn.so.7.6.5

HIP runtime version: N/A

MIOpen runtime version: N/A


Versions of relevant libraries:

[pip3] numpy==1.19.4
[pip3] torch==1.7.1+cu101
[pip3] torchaudio==0.7.2
pip3] torchsummary==1.5.1
[pip3] torchtext==0.3.1
[pip3] torchvision==0.8.2+cu101
[conda] Could not collect

Additional Context
Some of the things I have tried are:

Downloading and loading the dataset on seperate lines. e.g:

# Download the dataset only
datasets.CelebA(data_root, download=True)
# Load the dataset here
celeba_data = datasets.CelebA(data_root, download=False, transforms=...)


Using the ImageFolder dataset class instead of the CelebA class. e.g:

# Download the dataset only
datasets.CelebA(data_root, download=True)
# Load the dataset using the ImageFolder class
celeba_data = datasets.ImageFolder(data_root, transforms=...)

The memory problem is still persistent in either of the cases.

I did not manage to find a solution to the memory problem. However, I came up with a workaround, custom dataset. Here is my implementation:
import os
import zipfile 
import gdown
import torch
from natsort import natsorted
from PIL import Image
from torch.utils.data import Dataset
from torchvision import transforms

## Setup
# Number of gpus available
ngpu = 1
device = torch.device('cuda:0' if (
    torch.cuda.is_available() and ngpu &gt; 0) else 'cpu')

## Fetch data from Google Drive 
# Root directory for the dataset
data_root = 'data/celeba'
# Path to folder with the dataset
dataset_folder = f'{data_root}/img_align_celeba'
# URL for the CelebA dataset
url = 'https://drive.google.com/uc?id=1cNIac61PSA_LqDFYFUeyaQYekYPc75NH'
# Path to download the dataset to
download_path = f'{data_root}/img_align_celeba.zip'

# Create required directories 
if not os.path.exists(data_root):
  os.makedirs(data_root)
  os.makedirs(dataset_folder)

# Download the dataset from google drive
gdown.download(url, download_path, quiet=False)

# Unzip the downloaded file 
with zipfile.ZipFile(download_path, 'r') as ziphandler:
  ziphandler.extractall(dataset_folder)

## Create a custom Dataset class
class CelebADataset(Dataset):
  def __init__(self, root_dir, transform=None):
    &quot;&quot;&quot;
    Args:
      root_dir (string): Directory with all the images
      transform (callable, optional): transform to be applied to each image sample
    &quot;&quot;&quot;
    # Read names of images in the root directory
    image_names = os.listdir(root_dir)

    self.root_dir = root_dir
    self.transform = transform 
    self.image_names = natsorted(image_names)

  def __len__(self): 
    return len(self.image_names)

  def __getitem__(self, idx):
    # Get the path to the image 
    img_path = os.path.join(self.root_dir, self.image_names[idx])
    # Load image and convert it to RGB
    img = Image.open(img_path).convert('RGB')
    # Apply transformations to the image
    if self.transform:
      img = self.transform(img)

    return img

## Load the dataset 
# Path to directory with all the images
img_folder = f'{dataset_folder}/img_align_celeba'
# Spatial size of training images, images are resized to this size.
image_size = 64
# Transformations to be applied to each individual image sample
transform=transforms.Compose([
    transforms.Resize(image_size),
    transforms.CenterCrop(image_size),
    transforms.ToTensor(),
    transforms.Normalize(mean=[0.5, 0.5, 0.5],
                          std=[0.5, 0.5, 0.5])
])
# Load the dataset from file and apply transformations
celeba_dataset = CelebADataset(img_folder, transform)

## Create a dataloader 
# Batch size during training
batch_size = 128
# Number of workers for the dataloader
num_workers = 0 if device.type == 'cuda' else 2
# Whether to put fetched data tensors to pinned memory
pin_memory = True if device.type == 'cuda' else False

celeba_dataloader = torch.utils.data.DataLoader(celeba_dataset,
                                                batch_size=batch_size,
                                                num_workers=num_workers,
                                                pin_memory=pin_memory,
                                                shuffle=True)

This implementation is memory efficient and works for my use case, even during training the memory used averages around(4GB). I would however, appreciate further intuition as to what might be causing the memory problems.
