How to give a constant input to keras
Solution 1
You can create a static input using the tensor argument as described by jdehesa, however the tensor should be a Keras (not tensorflow) variable. You can create this as follows:
from keras.layers import Input
from keras import backend as K
constants = [1,2,3]
k_constants = K.variable(constants)
fixed_input = Input(tensor=k_constants)
Solution 2
EDIT: Apparently the answer below does not work (nowadays anyway). See Creating constant value in Keras for a related answer.
Looking at the source (I haven't been able to find a reference in the docs), it looks like you can just use Input
and pass it a constant Theano/TensorFlow tensor.
from keras.layers import Input
import tensorflow as tf
fixed_input = Input(tensor=tf.constant([1, 2, 3, 4]))
This will "wrap" the tensor (actually more like "extend" it with metadata) so you can use it with any Keras layer.
Solution 3
Something to add: When you come to compile the model you need to give the constant input as an input otherwise the graph disconnects
#your input
inputs = Input(shape = (input_shape,))
# an array of ones
constants = [1] * input_shape
# make the array a variable
k_constants = K.variable(constants, name = "ones_variable")
# make the variable a tensor
ones_tensor = Input(tensor=k_constants, name = "ones_tensor")
# do some layers
inputs = (Some_Layers())(inputs)
# get the complementary of the outputs
output = Subtract()([ones_tensor,inputs])
model = Model([inputs, ones_tensor],output)
model.complie(some_params)
when you train you can just feed in the data you have, you don't need the constant layer anymore.
I have found that no matter what you try it's usually easier to just use a custom layer and take advantage of the power of numpy:
class Complementry(Layer):
def __init__(self, **kwargs):
super(Complementry, self).__init__(**kwargs)
def build(self, input_shape):
super(Complementry, self).build(input_shape) # Be sure to call this at the end
def call(self, x):
return 1-x # here use MyArray + x
Yakku
Updated on June 04, 2022Comments
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Yakku almost 2 years
My network has two time-series inputs. One of the input has a fixed vector repeating for every time step. Is there an elegant way to load this fixed vector into the model just once and use it for computation?
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Zach over 5 yearsHow would I make and fit a model using these constants? Do I also have to provide the constants at fit time?
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Zach over 5 yearsHow would I make and fit a model using these constants? Do I also have to provide the constants at fit time?
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azureai about 5 yearsFor an actual solution see stackoverflow.com/questions/46465813/…
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azureai about 5 yearsThis does not work. But you gave a working solution in another thread: stackoverflow.com/questions/46465813/…
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Edu over 4 years@azureai it works for me. It's actually described in the documentation as well