Keras provides two different ways to define the architecture of a neural network: the Sequential Model and the Functional API. Both of these methods can be used to create a Keras model, but they have some differences:
1. Sequential Model: The Sequential Model is a linear stack of layers, and it’s the simplest and most common way to build a neural network in Keras. You can add layers to the model one by one, and each layer will be connected to the previous layer automatically. It’s easy to use and understand, especially for beginners. Additionally, the Sequential model supports most of the common layers that are used in deep learning. However, it’s not suitable for building complex models since it’s not flexible enough.
Here’s an example of how to create a Sequential model in Keras:
from keras.models import Sequential
from keras.layers import Dense
model = Sequential()
model.add(Dense(units=64, activation='relu', input_dim=100))
model.add(Dense(units=10, activation='softmax'))2. Functional API: The Functional API allows you to define complex models that have multiple inputs, outputs, and layers that are not connected sequentially. It’s more flexible than the Sequential model, and it can handle more complex architectures such as multi-input and multi-output models. Moreover, the Functional API enables you to define shared layers or weight-sharing models, which can be useful in some situations. However, it can be more challenging to use and understand, especially for beginners.
Here’s an example of how to create a simple model using the Functional API in Keras:
from keras.layers import Input, Dense
from keras.models import Model
inputs = Input(shape=(100,))
x = Dense(units=64, activation='relu')(inputs)
predictions = Dense(units=10, activation='softmax')(x)
model = Model(inputs=inputs, outputs=predictions)In summary, the Sequential model is a basic and easy-to-use way of building a neural network in Keras, while the Functional API is a more flexible way of building complex models with multiple inputs and outputs. If your model has a straightforward architecture, the Sequential model is generally easier to use. However, if you need a more complex architecture with multiple inputs, outputs, or shared layers, the Functional API is the way to go.