/pytorch2keras

PyTorch to Keras model convertor

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pytorch2keras

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PyTorch to Keras model converter.

Installation

pip install pytorch2keras 

Important notice

To use the converter properly, please, make changes in your ~/.keras/keras.json:

...
"backend": "tensorflow",
"image_data_format": "channels_first",
...

PyTorch 0.4.1 and greater

There is the problem related to a new version:

To make it work, please, cast all your .view() parameters to int. For example:

class ResNet(torchvision.models.resnet.ResNet):
    def __init__(self, *args, **kwargs):
        super(ResNet, self).__init__(*args, **kwargs)

    def forward(self, x):
        x = self.conv1(x)
        x = self.bn1(x)
        x = self.relu(x)
        x = self.maxpool(x)

        x = self.layer1(x)
        x = self.layer2(x)
        x = self.layer3(x)
        x = self.layer4(x)

        x = self.avgpool(x)
        x = x.view(int(x.size(0)), -1)  #  << Here
        x = self.fc(x)
        return x

Tensorflow.js

For the proper conversion to a tensorflow.js format, please use the new flag names='short'.

Here is a short instruction how to get a tensorflow.js model:

  1. First of all, you have to convert your model to Keras with this converter:
k_model = pytorch_to_keras(model, input_var, [(10, 32, 32,)], verbose=True, names='short')  
  1. Now you have Keras model. You can save it as h5 file and then convert it with tensorflowjs_converter but it doesn't work sometimes. As alternative, you may get Tensorflow Graph and save it as a frozen model:
# Function below copied from here:
# https://stackoverflow.com/questions/45466020/how-to-export-keras-h5-to-tensorflow-pb 
def freeze_session(session, keep_var_names=None, output_names=None, clear_devices=True):
    """
    Freezes the state of a session into a pruned computation graph.

    Creates a new computation graph where variable nodes are replaced by
    constants taking their current value in the session. The new graph will be
    pruned so subgraphs that are not necessary to compute the requested
    outputs are removed.
    @param session The TensorFlow session to be frozen.
    @param keep_var_names A list of variable names that should not be frozen,
                          or None to freeze all the variables in the graph.
    @param output_names Names of the relevant graph outputs.
    @param clear_devices Remove the device directives from the graph for better portability.
    @return The frozen graph definition.
    """
    from tensorflow.python.framework.graph_util import convert_variables_to_constants
    graph = session.graph
    with graph.as_default():
        freeze_var_names = \
            list(set(v.op.name for v in tf.global_variables()).difference(keep_var_names or []))
        output_names = output_names or []
        output_names += [v.op.name for v in tf.global_variables()]
        input_graph_def = graph.as_graph_def()
        if clear_devices:
            for node in input_graph_def.node:
                node.device = ""
        frozen_graph = convert_variables_to_constants(session, input_graph_def,
                                                      output_names, freeze_var_names)
        return frozen_graph


from keras import backend as K
import tensorflow as tf
frozen_graph = freeze_session(K.get_session(),
                              output_names=[out.op.name for out in k_model.outputs])

tf.train.write_graph(frozen_graph, ".", "my_model.pb", as_text=False)
print([i for i in k_model.outputs])

  1. You will see the output layer name, so, now it's time to convert my_model.pb to tfjs model:
tensorflowjs_converter  \
    --input_format=tf_frozen_model \
    --output_node_names='TANHTObs/Tanh' \
    my_model.pb \
    model_tfjs
  1. Thats all!
const MODEL_URL = `model_tfjs/tensorflowjs_model.pb`;
const WEIGHTS_URL = `model_tfjs/weights_manifest.json`;
cont model = await tf.loadFrozenModel(MODEL_URL, WEIGHTS_URL);

How to use

It's the converter of PyTorch graph to a Keras (Tensorflow backend) model.

Firstly, we need to load (or create) a valid PyTorch model:

class TestConv2d(nn.Module):
    """
    Module for Conv2d testing
    """

    def __init__(self, inp=10, out=16, kernel_size=3):
        super(TestConv2d, self).__init__()
        self.conv2d = nn.Conv2d(inp, out, stride=1, kernel_size=kernel_size, bias=True)

    def forward(self, x):
        x = self.conv2d(x)
        return x

model = TestConv2d()

# load weights here
# model.load_state_dict(torch.load(path_to_weights.pth))

The next step - create a dummy variable with correct shape:

input_np = np.random.uniform(0, 1, (1, 10, 32, 32))
input_var = Variable(torch.FloatTensor(input_np))

We use the dummy-variable to trace the model (with jit.trace):

from converter import pytorch_to_keras
# we should specify shape of the input tensor
k_model = pytorch_to_keras(model, input_var, [(10, 32, 32,)], verbose=True)  

You can also set H and W dimensions to None to make your model shape-agnostic (e.g. fully convolutional netowrk):

from pytorch2keras.converter import pytorch_to_keras
# we should specify shape of the input tensor
k_model = pytorch_to_keras(model, input_var, [(10, None, None,)], verbose=True)  

That's all! If all the modules have converted properly, the Keras model will be stored in the k_model variable.

API

Here is the only method pytorch_to_keras from pytorch2keras module.

def pytorch_to_keras(
    model, args, input_shapes,
    change_ordering=False, training=False, verbose=False, names=False,
)

Options:

  • model -- a PyTorch module to convert;
  • args -- list of dummy variables with proper shapes;
  • input_shapes -- list with shape tuples;
  • change_ordering -- boolean, if enabled, the converter will try to change BCHW to BHWC
  • training -- boolean, switch model to training mode (never use it)
  • verbose -- boolean, verbose output
  • names -- choice from [keep, short, random]. The selector set the target layer naming policy.

Supported layers

  • Activations:

    • ReLU
    • LeakyReLU
    • SELU
    • Sigmoid
    • Softmax
    • Tanh
    • HardTanh
  • Constants

  • Convolutions:

    • Conv1d
    • Conv2d
    • ConvTrsnpose2d
  • Element-wise:

    • Add
    • Mul
    • Sub
    • Div
  • Embedding

  • Linear

  • Normalizations:

    • BatchNorm2d
    • InstanceNorm2d
    • Dropout
  • Poolings:

    • MaxPool2d
    • AvgPool2d
    • Global MaxPool2d (adaptive pooling to shape [1, 1])
    • Global AvgPool2d (adaptive pooling to shape [1, 1])
  • Not tested yet:

    • Upsampling
    • Padding
    • Reshape

Models converted with pytorch2keras

  • ResNet*
  • VGG*
  • PreResNet*
  • SqueezeNet (with ceil_mode=False)
  • SqueezeNext
  • DenseNet*
  • AlexNet
  • Inception
  • SeNet
  • Mobilenet v2
  • DiracNet
  • DARTS
  • DRNC
Model Top1 Top5 Params FLOPs Source weights Remarks
ResNet-10 37.09 15.55 5,418,792 892.62M osmr's repo Success
ResNet-12 35.86 14.46 5,492,776 1,124.23M osmr's repo Success
ResNet-14 32.85 12.41 5,788,200 1,355.64M osmr's repo Success
ResNet-16 30.68 11.10 6,968,872 1,586.95M osmr's repo Success
ResNet-18 x0.25 49.16 24.45 831,096 136.64M osmr's repo Success
ResNet-18 x0.5 36.54 14.96 3,055,880 485.22M osmr's repo Success
ResNet-18 x0.75 33.25 12.54 6,675,352 1,045.75M osmr's repo Success
ResNet-18 29.13 9.94 11,689,512 1,818.21M osmr's repo Success
ResNet-34 25.34 7.92 21,797,672 3,669.16M osmr's repo Success
ResNet-50 23.50 6.87 25,557,032 3,868.96M osmr's repo Success
ResNet-50b 22.92 6.44 25,557,032 4,100.70M osmr's repo Success
ResNet-101 21.66 5.99 44,549,160 7,586.30M osmr's repo Success
ResNet-101b 21.18 5.60 44,549,160 7,818.04M osmr's repo Success
ResNet-152 21.01 5.61 60,192,808 11,304.85M osmr's repo Success
ResNet-152b 20.54 5.37 60,192,808 11,536.58M osmr's repo Success
PreResNet-18 28.72 9.88 11,687,848 1,818.41M osmr's repo Success
PreResNet-34 25.88 8.11 21,796,008 3,669.36M osmr's repo Success
PreResNet-50 23.39 6.68 25,549,480 3,869.16M osmr's repo Success
PreResNet-50b 23.16 6.64 25,549,480 4,100.90M osmr's repo Success
PreResNet-101 21.45 5.75 44,541,608 7,586.50M osmr's repo Success
PreResNet-101b 21.73 5.88 44,541,608 7,818.24M osmr's repo Success
PreResNet-152 20.70 5.32 60,185,256 11,305.05M osmr's repo Success
PreResNet-152b 21.00 5.75 60,185,256 11,536.78M Gluon Model Zoo Success
PreResNet-200b 21.10 5.64 64,666,280 15,040.27M tornadomeet/ResNet Success
DenseNet-121 25.11 7.80 7,978,856 2,852.39M Gluon Model Zoo Success
DenseNet-161 22.40 6.18 28,681,000 7,761.25M Gluon Model Zoo Success
DenseNet-169 23.89 6.89 14,149,480 3,381.48M Gluon Model Zoo Success
DenseNet-201 22.71 6.36 20,013,928 4,318.75M Gluon Model Zoo Success
DarkNet Tiny 40.31 17.46 1,042,104 496.34M osmr's repo Success
DarkNet Ref 38.00 16.68 7,319,416 365.55M osmr's repo Success
SqueezeNet v1.0 40.97 18.96 1,248,424 828.30M osmr's repo Success
SqueezeNet v1.1 39.09 17.39 1,235,496 354.88M osmr's repo Success
MobileNet x0.25 45.78 22.18 470,072 42.30M osmr's repo Success
MobileNet x0.5 36.12 14.81 1,331,592 152.04M osmr's repo Success
MobileNet x0.75 32.71 12.28 2,585,560 329.22M Gluon Model Zoo Success
MobileNet x1.0 29.25 10.03 4,231,976 573.83M Gluon Model Zoo Success
FD-MobileNet x0.25 56.19 31.38 383,160 12.44M osmr's repo Success
FD-MobileNet x0.5 42.62 19.69 993,928 40.93M osmr's repo Success
FD-MobileNet x1.0 35.95 14.72 2,901,288 146.08M clavichord93/FD-MobileNet Success
MobileNetV2 x0.25 48.89 25.24 1,516,392 32.22M Gluon Model Zoo Success
MobileNetV2 x0.5 35.51 14.64 1,964,736 95.62M Gluon Model Zoo Success
MobileNetV2 x0.75 30.82 11.26 2,627,592 191.61M Gluon Model Zoo Success
MobileNetV2 x1.0 28.51 9.90 3,504,960 320.19M Gluon Model Zoo Success
InceptionV3 21.22 5.59 23,834,568 5,746.72M Gluon Model Zoo Success
DiracNetV2-18 31.47 11.70 11,511,784 1,798.43M szagoruyko/diracnets Success
DiracNetV2-34 28.75 9.93 21,616,232 3,649.37M szagoruyko/diracnets Success
DARTS 26.70 8.74 4,718,752 537.64M szagoruyko/diracnets Success

Usage

Look at the tests directory.

License

This software is covered by MIT License.