MemCNN

A PyTorch framework for developing memory-efficient invertible neural networks.

• Free software: MIT license (please cite our work if you use it)
• Documentation: https://memcnn.readthedocs.io.
• Installation: https://memcnn.readthedocs.io/en/latest/installation.html

Features

• Enable memory savings during training by wrapping arbitrary invertible PyTorch functions with the InvertibleModuleWrapper class.
• Simple toggling of memory saving by setting the keep_input property of the InvertibleModuleWrapper.
• Turn arbitrary non-linear PyTorch functions into invertible versions using the AdditiveCoupling or the AffineCoupling classes.
• Training and evaluation code for reproducing RevNet experiments using MemCNN.
• CI tests for Python v3.7 and torch v1.0, v1.1, v1.4 and v1.7 with good code coverage.

Examples

Creating an AdditiveCoupling with memory savings

import torch
import torch.nn as nn
import memcnn


# define a new torch Module with a sequence of operations: Relu o BatchNorm2d o Conv2d
class ExampleOperation(nn.Module):
    def __init__(self, channels):
        super(ExampleOperation, self).__init__()
        self.seq = nn.Sequential(
                                    nn.Conv2d(in_channels=channels, out_channels=channels,
                                              kernel_size=(3, 3), padding=1),
                                    nn.BatchNorm2d(num_features=channels),
                                    nn.ReLU(inplace=True)
                                )

    def forward(self, x):
        return self.seq(x)


# generate some random input data (batch_size, num_channels, y_elements, x_elements)
X = torch.rand(2, 10, 8, 8)

# application of the operation(s) the normal way
model_normal = ExampleOperation(channels=10)
model_normal.eval()

Y = model_normal(X)

# turn the ExampleOperation invertible using an additive coupling
invertible_module = memcnn.AdditiveCoupling(
    Fm=ExampleOperation(channels=10 // 2),
    Gm=ExampleOperation(channels=10 // 2)
)

# test that it is actually a valid invertible module (has a valid inverse method)
assert memcnn.is_invertible_module(invertible_module, test_input_shape=X.shape)

# wrap our invertible_module using the InvertibleModuleWrapper and benefit from memory savings during training
invertible_module_wrapper = memcnn.InvertibleModuleWrapper(fn=invertible_module, keep_input=True, keep_input_inverse=True)

# by default the module is set to training, the following sets this to evaluation
# note that this is required to pass input tensors to the model with requires_grad=False (inference only)
invertible_module_wrapper.eval()

# test that the wrapped module is also a valid invertible module
assert memcnn.is_invertible_module(invertible_module_wrapper, test_input_shape=X.shape)

# compute the forward pass using the wrapper
Y2 = invertible_module_wrapper.forward(X)

# the input (X) can be approximated (X2) by applying the inverse method of the wrapper on Y2
X2 = invertible_module_wrapper.inverse(Y2)

# test that the input and approximation are similar
assert torch.allclose(X, X2, atol=1e-06)

Run PyTorch Experiments

After installing MemCNN run:

python -m memcnn.train [MODEL] [DATASET] [--fresh] [--no-cuda]

• Available values for DATASET are cifar10 and cifar100.
• Available values for MODEL are resnet32, resnet110, resnet164, revnet38, revnet110, revnet164
• Use the --fresh flag to remove earlier experiment results.
• Use the --no-cuda flag to train on the CPU rather than the GPU through CUDA.

Datasets are automatically downloaded if they are not available.

When using Python 3.* replace the python directive with the appropriate Python 3 directive. For example when using the MemCNN docker image use python3.6.

When MemCNN was installed using pip or from sources you might need to setup a configuration file before running this command. Read the corresponding section about how to do this here: https://memcnn.readthedocs.io/en/latest/installation.html

Results

TensorFlow results were obtained from the reversible residual network running the code from their GitHub.

The PyTorch results listed were recomputed on June 11th 2018, and differ from the results in the ICLR paper. The Tensorflow results are still the same.

Prediction accuracy

	Cifar-10		Cifar-100
Model	Tensorflow	PyTorch	Tensorflow	PyTorch
resnet-32	92.74	92.86	69.10	69.81
resnet-110	93.99	93.55	73.30	72.40
resnet-164	94.57	94.80	76.79	76.47
revnet-38	93.14	92.80	71.17	69.90
revnet-110	94.02	94.10	74.00	73.30
revnet-164	94.56	94.90	76.39	76.90

Training time (hours : minutes)

	Cifar-10		Cifar-100
Model	Tensorflow	PyTorch	Tensorflow	PyTorch
resnet-32	2:04	1:51	1:58	1:51
resnet-110	4:11	2:51	6:44	2:39
resnet-164	11:05	4:59	10:59	3:45
revnet-38	2:17	2:09	2:20	2:16
revnet-110	6:59	3:42	7:03	3:50
revnet-164	13:09	7:21	13:12	7:17

Memory consumption of model training in PyTorch

Layers		Parameters		Parameters (MB)		Activations (MB)
ResNet	RevNet	ResNet	RevNet	ResNet	RevNet	ResNet	RevNet
32	38	466906	573994	1.9	2.3	238.6	85.6
110	110	1730714	1854890	6.8	7.3	810.7	85.7
164	164	1704154	1983786	6.8	7.9	2452.8	432.7

The ResNet model is the conventional Residual Network implementation in PyTorch, while the RevNet model uses the memcnn.InvertibleModuleWrapper to achieve memory savings.

Works using MemCNN

• MemCNN: a Framework for Developing Memory Efficient Deep Invertible Networks by Sil C. van de Leemput et al.
• Reversible GANs for Memory-efficient Image-to-Image Translation by Tycho van der Ouderaa et al.
• Chest CT Super-resolution and Domain-adaptation using Memory-efficient 3D Reversible GANs by Tycho van der Ouderaa et al.
• iUNets: Fully invertible U-Nets with Learnable Up- and Downsampling by Christian Etmann et al.

Citation

Sil C. van de Leemput, Jonas Teuwen, Bram van Ginneken, and Rashindra Manniesing. MemCNN: A Python/PyTorch package for creating memory-efficient invertible neural networks. Journal of Open Source Software, 4, 1576, http://dx.doi.org/10.21105/joss.01576, 2019.

If you use our code, please cite:

@article{vandeLeemput2019MemCNN,
  journal = {Journal of Open Source Software},
  doi = {10.21105/joss.01576},
  issn = {2475-9066},
  number = {39},
  publisher = {The Open Journal},
  title = {MemCNN: A Python/PyTorch package for creating memory-efficient invertible neural networks},
  url = {http://dx.doi.org/10.21105/joss.01576},
  volume = {4},
  author = {Sil C. {van de} Leemput and Jonas Teuwen and Bram {van} Ginneken and Rashindra Manniesing},
  pages = {1576},
  date = {2019-07-30},
  year = {2019},
  month = {7},
  day = {30},
}