I am trying to implement Custom version of PRElu activation function in tensorflow.
The custom thing about this activation is the knee of the relu is smoothed. I got the equation from this link:
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 stack oveflow post :
https://datascience.stackexchange.com/questions/58884/how-to-create-custom-activation-functions-in-keras-tensorflow
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 dont understand this error. Dose anyone know how to implement this function as custom activation function with trainable parameters alpha and u.
Need Help!
>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)