Issue
I am trying to implement a custom version of the PElu activation function in tensorflow. The custom thing about this activation is the knee of the relu is smoothed. I got the equation from this paper.
Here is the code:
from keras import backend as K
import tensorflow as tf
def SMU_LeakyPRElu(x, alpha=2.5,u=1.0):
return ((1+alpha)*x)+((1-alpha)*x)*(tf.math.erf(u*(1-alpha)*x))
from keras.layers import Layer
class SMU_LeakyPRElu(Layer):
def __init__(self, alpha=2.5, u=1.0, trainable=False, **kwargs):
super(SMU_LeakyPRElu, self).__init__(**kwargs)
self.supports_masking = True
self.alpha = alpha
self.u = u
self.trainable = trainable
def build(self, input_shape):
self.alpha_factor = K.variable(self.alpha,
dtype=K.floatx(),
name='alpha_factor')
self.u_factor = K.variable(self.u,
dtype=K.floatx(),
name='u_factor')
if self.trainable:
self._trainable_weights.append(self.alpha_factor)
self._trainable_weights.append(self.u_factor)
super(SMU_LeakyPRElu, self).build(input_shape)
def call(self, inputs, mask=None):
return SMU_LeakyPRElu(inputs, self.alpha_factor,self.u_factor)
def get_config(self):
config = {'alpha': self.get_weights()[0] if self.trainable else self.alpha,
'u' : self.get_weights()[1] if self.trainable else self.u,
'trainable': self.trainable}
base_config = super(SMU_LeakyPRElu, self).get_config()
return dict(list(base_config.items()) + list(config.items()))
def compute_output_shape(self, input_shape):
return input_shape
x = tf.random.normal((1,10,4))
print(x)
input_shape = (1,10,4)
input_layer = tf.keras.layers.Input(shape=input_shape[1:], name="input_layer")
layer_1 = tf.keras.layers.Conv1D(2, 1,padding = 'valid', input_shape=input_shape[:1])(input_layer)
layer_2 = SMU_LeakyPRElu(alpha=2.5,u=1.0,trainable=True)(layer_1)
model = tf.keras.models.Model(input_layer, layer_2, name="model")
model.compile(optimizer=tf.keras.optimizers.Adam(learning_rate=0.0005), loss="categorical_crossentropy", run_eagerly=True)
print(model.summary())
result = model.predict(x)
print(result)
print(result.shape)
I implemented this code using a example from this post at Data Science SE.
Error:
tf.Tensor(
[[[ 1.0467066 -1.1833347 1.5384735 2.078511 ]
[-1.6025988 -0.30846047 0.8019808 0.3113866 ]
[ 0.58313304 -0.90643036 -0.3926888 -0.6210553 ]
[ 0.16505387 -0.5930619 0.6983522 -0.12211661]
[ 0.06077941 -0.11117186 -1.2540722 -0.32234746]
[ 0.41838828 0.7090619 0.30999053 0.10459523]
[ 0.35603598 -0.2695868 -0.17901018 -0.09100233]
[ 1.2746769 0.8311447 0.02825974 -0.48021472]
[-1.536545 -0.24765234 -0.36437735 -1.1891246 ]
[ 0.7531206 -0.56109476 -0.65761757 0.19102335]]], shape=(1, 10, 4), dtype=float32)
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-50-c9d490dfd533> in <module>
5 input_layer = tf.keras.layers.Input(shape=input_shape[1:], name="input_layer")
6 layer_1 = tf.keras.layers.Conv1D(2, 1,padding = 'valid', input_shape=input_shape[:1])(input_layer)
----> 7 layer_2 = SMU_LeakyPRElu(alpha=2.5,u=1.0,trainable=True)(layer_1)
8
9 model = tf.keras.models.Model(input_layer, layer_2, name="model")
1 frames
/usr/local/lib/python3.7/dist-packages/tensorflow/python/framework/type_spec.py in type_spec_from_value(value)
888 3, "Failed to convert %r to tensor: %s" % (type(value).__name__, e))
889
--> 890 raise TypeError(f"Could not build a TypeSpec for {value} of "
891 f"unsupported type {type(value)}.")
892
TypeError: Could not build a TypeSpec for <__main__.SMU_LeakyPRElu object at 0x7fde698f7850> of unsupported type <class '__main__.SMU_LeakyPRElu'>.
I don’t understand this error. How should I implement this function as custom activation function with trainable parameters alpha and u.?
Solution
The problem is that you have named your activation function and the custom layer you created the same thing. I refactored your code for you.
Code:
import tensorflow as tf
from typing import Optional
from tensorflow.keras import Model
from tensorflow.keras.layers import Conv1D
from tensorflow.keras.layers import Input
from tensorflow.keras.layers import Layer
from tensorflow.keras.optimizers import Adam
class SMULeakyPReLU(Layer):
"""``SMULeakyPReLU``."""
def __init__(self,
alpha: float = 2.5,
u: float = 1.,
trainable: bool = False,
**kwargs):
super().__init__(**kwargs)
self.alpha = alpha
self.u = u
self.trainable = trainable
def build(self, input_shape: tf.TensorShape):
super().build(input_shape)
self.alpha_factor = tf.Variable(
self.alpha,
dtype=tf.float32,
trainable=self.trainable,
name="alpha_factor")
self.u_factor = tf.Variable(
self.u,
dtype=tf.float32,
name="u_factor")
def call(self,
inputs: tf.Tensor,
mask: Optional[tf.Tensor] = None
) -> tf.Tensor:
fst = (1. + self.alpha_factor) * inputs
snd = (1. - self.alpha_factor) * inputs
trd = tf.math.erf(self.u_factor * (1. - self.alpha_factor) * inputs)
return fst * snd * trd
def get_config(self):
config = {
"alpha": self.get_weights()[0] if self.trainable else self.alpha,
"u": self.get_weights()[1] if self.trainable else self.u,
"trainable": self.trainable
}
base_config = super().get_config()
return dict(list(base_config.items()) + list(config.items()))
Test
# fake data
x = tf.random.normal((1, 10, 4))
# create network
input_layer = Input(shape=x.shape[1:], name="input_layer")
layer_1 = Conv1D(2, 1, padding="valid")(input_layer)
layer_2 = SMULeakyPReLU(alpha=2.5, u=1.0, trainable=True)(layer_1)
# create model
model = Model(input_layer, layer_2, name="model")
# compile model and summary
model.compile(
optimizer=Adam(learning_rate=5e-4),
loss="categorical_crossentropy",
run_eagerly=True)
print(model.summary())
# forward pass
result = model.predict(x)
print(result)
print(result.shape)
# Model: "model"
# _________________________________________________________________
# Layer (type) Output Shape Param #
# =================================================================
# input_layer (InputLayer) [(None, 10, 4)] 0
#
# conv1d_1 (Conv1D) (None, 10, 2) 10
#
# smu_leaky_p_re_lu_1 (SMULea (None, 10, 2) 2
# kyPReLU)
#
# =================================================================
# Total params: 12
# Trainable params: 12
# Non-trainable params: 0
# _________________________________________________________________
# None
# 1/1 [==============================] - 0s 13ms/step
# [[[-1.6503611e+01 -3.5051659e+01]
# [ 4.0098205e-02 1.5923592e+00]
# [-1.4898951e+00 7.5487376e-05]
# [ 3.1900513e+01 2.8786476e+01]
# [ 1.9207695e+01 3.6511238e+01]
# [-6.8302655e-01 -4.7705490e-02]
# [ 9.6008554e-03 7.5611029e+00]
# [ 4.7136435e-01 2.5528276e+00]
# [ 2.6859209e-01 3.3496175e+00]
# [ 1.4372441e+01 3.4978668e+01]]]
# (1, 10, 2)
Answered By – o-90
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