Is there any way to access layers in tensorflow_hub.KerasLayer object?

问题

I am trying to use a pre-trained model from tensorflow hub into my object detection model. I wrapped a model from hub as a KerasLayer object following the official instruction. Then I realized that I cannot access the layers in this pre-trained model. But I need to use outputs from some specific layers to build my model. Is there any way to access layers in tensorflow_hub.KerasLayer object?

回答1:

For one to be able to do that easily, the creator of the pretrained model would have needed to make that output ready to be accessed. E.g. by having an extra function or an extra signature that outputs the activation you want to use.

回答2:

There is an undocumented way to get intermediate layers out of some TF2 SavedModels exported from TF-Slim, such as https://tfhub.dev/google/imagenet/inception_v1/feature_vector/4: passing return_endpoints=True to the SavedModel's __call__ function changes the output to a dict.

NOTE: This interface is subject to change or removal, and has known issues.

model = tfhub.KerasLayer('https://tfhub.dev/google/imagenet/inception_v1/feature_vector/4', trainable=False, arguments=dict(return_endpoints=True))
input = tf.keras.layers.Input((224, 224, 3))
outputs = model(input)
for k, v in sorted(outputs.items()):
  print(k, v.shape)

Output for this example:

InceptionV1/Conv2d_1a_7x7 (None, 112, 112, 64)
InceptionV1/Conv2d_2b_1x1 (None, 56, 56, 64)
InceptionV1/Conv2d_2c_3x3 (None, 56, 56, 192)
InceptionV1/MaxPool_2a_3x3 (None, 56, 56, 64)
InceptionV1/MaxPool_3a_3x3 (None, 28, 28, 192)
InceptionV1/MaxPool_4a_3x3 (None, 14, 14, 480)
InceptionV1/MaxPool_5a_2x2 (None, 7, 7, 832)
InceptionV1/Mixed_3b (None, 28, 28, 256)
InceptionV1/Mixed_3c (None, 28, 28, 480)
InceptionV1/Mixed_4b (None, 14, 14, 512)
InceptionV1/Mixed_4c (None, 14, 14, 512)
InceptionV1/Mixed_4d (None, 14, 14, 512)
InceptionV1/Mixed_4e (None, 14, 14, 528)
InceptionV1/Mixed_4f (None, 14, 14, 832)
InceptionV1/Mixed_5b (None, 7, 7, 832)
InceptionV1/Mixed_5c (None, 7, 7, 1024)
InceptionV1/global_pool (None, 1, 1, 1024)
default (None, 1024)

Issues to be aware of:

• Undocumented, subject to change or removal, not available consistently.
• __call__ computes all outputs (and applies all update ops during training) irrespective of the ones being used later on.

Source: https://github.com/tensorflow/hub/issues/453

来源：https://stackoverflow.com/questions/61996588/is-there-any-way-to-access-layers-in-tensorflow-hub-keraslayer-object