How to convert Keras h5 to PyTorch pth format?

Question

I have trained a feature extractor in Keras and saved the weights as a h5 file. Now I want to load the same weights into the same model created and initialized in PyTorch for performance comparisons. Is there any way I can convert the h5 file to pth file so I can load that into the PyTorch model?

Answer 1

You must be careful with the versions from TF and PyTorch (as some commands may be different).

Basically you must:

1 - Know your layer and activation structure on Keras:

You can get the layer information with:

model_keras.summary()

If you can't get info about activation functions, try:

for layer in model_keras.layers:
    print(layer.output)

2 - Build a model on PyTorch that has the same layer structure (and activation) as on Keras

3 - The recently created PyTorch model (let's say model_pyt) has different weights and biases from your model on Keras, so you must copy those weights and biases from the Keras model to PyTorch model:

BE CAREFUL HERE, PYTORCH WEIGHTS ARE TRANSPOSED IN RELATION TO KERAS WEIGHTS

Then, for example, copying a weight would be like:

model_pyt.layer1.weight.data = torch.tensor(model_keras.layers[0].get_weights()[0].T)

And for the bias:

model_pyt.layer1.bias.data = torch.tensor(model_keras.layers[0].get_weights()[1])

repeat that for all layers.

Then, your PyTorch model has the same architecture and weights as the Keras model and might behave in the same way.