Traing a CNN using Prelu activation function

I’m trying to train the model using prelu activation function, but I get the following error

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
/usr/local/lib/python3.7/dist-packages/tensorflow/python/ops/array_ops.py in zeros(shape, dtype, name)
   2965         shape = constant_op._tensor_shape_tensor_conversion_function(
-> 2966             tensor_shape.TensorShape(shape))
   2967       except (TypeError, ValueError):

31 frames
ValueError: Cannot convert a partially known TensorShape to a Tensor: (None, None, 64)

During handling of the above exception, another exception occurred:

ValueError                                Traceback (most recent call last)
/usr/local/lib/python3.7/dist-packages/tensorflow/python/framework/constant_op.py in convert_to_eager_tensor(value, ctx, dtype)
     96       dtype = dtypes.as_dtype(dtype).as_datatype_enum
     97   ctx.ensure_initialized()
---> 98   return ops.EagerTensor(value, ctx.device_name, dtype)
     99 
    100 

ValueError: Attempt to convert a value (None) with an unsupported type (<class 'NoneType'>) to a Tensor.

I’m using the below-mentioned code, kindly let me know how do I correct it.

from tensorflow.keras.applications import MobileNet
from tensorflow.keras.layers import (Conv2D, MaxPooling2D, 
                                     GlobalAveragePooling2D, Dropout, Dense)
from tensorflow.keras import Model
from tensorflow import keras

CLASSES = 2
#model.compile()

# setup model
base_model = MobileNet(weights='imagenet', include_top=False)
input = (224, 224, 3)
x = base_model.output
x = Conv2D(64, (3,3), padding='same', activation = keras.layers.PReLU(alpha_initializer='zeros', alpha_regularizer=None, alpha_constraint=None, shared_axes=None), strides= (2,2), name='layer1')(x)
x = MaxPooling2D(pool_size=(2,2))(x)

x = Conv2D(128, (3,3), padding='same', activation = keras.layers.PReLU(alpha_initializer='zeros', alpha_regularizer=None, alpha_constraint=None, shared_axes=None), name='layer2')(x)

x = GlobalAveragePooling2D(name='avg_pool')(x)

x = Dropout(0.4)(x)
predictions = Dense(CLASSES, activation=tf.keras.activations.sigmoid)(x)
model = Model(inputs=base_model.input, outputs=predictions)
 
# transfer learning
for layer in base_model.layers:
 layer.trainable = False
 
model.compile(optimizer='rmsprop',loss='categorical_crossentropy',metrics=['accuracy'])

Answer

Your tensor input is wrong. You need to set it up like this way

input_s = layers.Input((224, 224, 3))
base_model = keras.applications.MobileNet(weights='imagenet', 
                                 include_top=False, input_tensor=input_s)
...

Full working code

from tensorflow.keras.applications import MobileNet
from tensorflow.keras.layers import (Conv2D, MaxPooling2D, 
                                     GlobalAveragePooling2D, Dropout, Dense)
from tensorflow.keras import Model
from tensorflow import keras
from tensorflow.keras import layers
import tensorflow as tf 

CLASSES = 2
# setup model
input_s = layers.Input((224, 224, 3))
base_model = keras.applications.MobileNet(weights='imagenet', 
                      include_top=False, input_tensor=input_s)
x = layers.Conv2D(64, (3,3), padding='same', 
                  activation = keras.layers.PReLU(
                      alpha_initializer='zeros', 
                      alpha_regularizer=None,
                       alpha_constraint=None, 
                       shared_axes=None), 
                  strides= (2,2), name='layer1')(base_model.output)
x = layers.MaxPooling2D(pool_size=(2,2))(x)
x = layers.Conv2D(128, (3,3), padding='same', 
                  activation = keras.layers.PReLU(alpha_initializer='zeros', 
                                                  alpha_regularizer=None, 
                                                  alpha_constraint=None, 
                                                  shared_axes=None), name='layer2')(x)

x = layers.GlobalAveragePooling2D(name='avg_pool')(x)
x = layers.Dropout(0.4)(x)

predictions = layers.Dense(CLASSES, 
                      activation=tf.keras.activations.sigmoid)(x)
model = tf.keras.Model(inputs=base_model.input, outputs=predictions)

# transfer learning
for layer in base_model.layers:
 layer.trainable = False

model.compile(optimizer='rmsprop',
              loss='categorical_crossentropy',
              metrics=['accuracy'])