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A PyTorch framework for developing memory efficient deep invertible networks.

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


  • 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.


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),

    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)

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)

# 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:

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