chasep255 chasep255 - 6 months ago 33
Python Question

Keras error with merge layer

I am trying to build a model to colorize images. I am using the LAB color space. The input to the model is the L channel and the model is to be trained to predict the A and B channels. I want to run the L channel through a few convolutions and then split it off into two other models which independently calculate the A and B channels. At the end I want to merge them back together to get the output.

model = Sequential()
model.add(InputLayer((1, H, W)))

model.add(Convolution2D(64, 5, 5, border_mode = 'same', activation = 'relu'))
model.add(Convolution2D(64, 5, 5, border_mode = 'same', activation = 'relu'))
last = Convolution2D(64, 5, 5, border_mode = 'same', activation = 'relu')
model.add(last)

a_model = Sequential()
a_model.add(last)
a_model.add(Convolution2D(64, 5, 5, border_mode = 'same', activation = 'relu'))
a_model.add(Convolution2D(64, 5, 5, border_mode = 'same', activation = 'relu'))
a_model.add(Convolution2D(1, 3, 3, border_mode = 'same', activation = 'sigmoid'))

b_model = Sequential()
b_model.add(last)
b_model.add(Convolution2D(64, 5, 5, border_mode = 'same', activation = 'relu'))
b_model.add(Convolution2D(64, 5, 5, border_mode = 'same', activation = 'relu'))
b_model.add(Convolution2D(1, 3, 3, border_mode = 'same', activation = 'sigmoid'))

model.add(Merge((a_model, b_model), mode = 'concat'))


I get the following error when I try to create the Merge layer.

Using Theano backend.
Using gpu device 0: GeForce GTX TITAN (CNMeM is disabled, cuDNN 5004)
Traceback (most recent call last):
File "/home/chase/workspace/Colorizer/colorizer2.py", line 79, in <module>
model.add(Merge((a_model, b_model), mode = 'concat'))
File "/usr/local/lib/python3.5/dist-packages/keras/engine/topology.py", line 1118, in __init__
self.add_inbound_node(layers, node_indices, tensor_indices)
File "/usr/local/lib/python3.5/dist-packages/keras/engine/topology.py", line 524, in add_inbound_node
assert len(node_indices) == len(inbound_layers)
AssertionError


I want the outut of the model to be (2, H, W) where H and W are the image height and width.

Answer

The Sequential model doesn't allow you to create forks in the network. Use the functional API (new in Keras 1.0) instead. You can follow this tutorial.