# What is TensorFlow

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## What is TensorFlow

TensorFlow is an open source Python library for complex numeric computation. It is a foundation library that can be used to create Machine Learning/Deep Learning neural network models, such as:

- Differentiable neural networks
- Deep network models that require gradient optimization

TensorFlow is an open source Python library for complex numeric computation. It is a foundation library that can be used to create Machine Learning/Deep Learning neural network models, such as:

- Differentiable neural networks
- Deep network models that require gradient optimization

TensorFlow’s low-level APIs can serve as the backend computational engine for a high level interface like Keras, which simplifies the definition and training of network models. For more information about Keras, refer to *What is a Keras Model**.*

**TensorFlow combines: **

**Symbolic Math**. Use of computers to calculate mathematical equations and expressions in symbolic form, eg.**x*y****Dataflow**. Disconnection of data components into data pipelines that execute concurrently.**Differentiable Programming**. Gradient based optimization involving differential functions.**Generalization**. In TensorFlow, a tensor is an abstraction over a multidimensional array. The essential meaning of a tensor as defined in tensor calculus is kept, but the formalism and details of tensor calculus are dropped.

**TensorFlow sacrifices user-friendless for power: **

- Efficient computation of mathematical expressions containing multi-dimensional arrays.
- Handles difficult, complex algorithms and models that other platforms cannot handle.
- Flexible enough for use cases requiring custom coding, yet able to automate many tasks with built-in algorithms and pre-trained models.
- Highly scalable from single machines to distributed networks with huge datasets.
- Can utilize CPU, TPU (Tensor Processing Unit), and GPU (Graphics Processing Unit) to perform computations.

**Start Using TensorFlow **

If you don’t have TensorFlow installed, refer to How To Install Keras And TensorFlow.

The easiest way to start working with TensorFlow is by using Keras, which integrates seamlessly as a high level interface for TensorFlow. The best way is to begin with the Keras Sequential API, and then try its Functional API. Once you are familiar with Keras (and its limitations), you can consider the more comprehensive TensorFlow platform.

For more information about Keras, refer to ‘*What is a Keras Model’*

**TensorFlow Keras Example**

In this example, a TensorFlow Keras application is created by combining the TensorFlow – foundation library with Keras classes (TensorFlow subclasses). We’ll define a simple CNN (Convolutional Neural Network) model for handwritten character recognition using the MNIST dataset:

# Import the required TensorFlow library # and Keras classes for this example: import tensorflow as tf from tensorflow.keras import Model from tensorflow.keras.models import Sequential from tensorflow.keras.layers import Dense, Flatten, Conv2D, AveragePooling2D # Load MNIST dataset and split into training and testing samples: mnist = tf.keras.datasets.mnist (x_train, y_train),(x_test, y_test) = mnist.load_data() # Reshape the image dimensions: x_train = x_train.reshape(x_train.shape[0], 28, 28, 1) x_test = x_test.reshape(x_test.shape[0], 28, 28, 1) # Normalize the output from the previous function: x_train = tf.keras.utils.normalize(x_train, axis=1) x_test = tf.keras.utils.normalize(x_test, axis=1) # Build the model: model = Sequential() model.add(Conv2D(filters=6, kernel_size=(3, 3), activation='tanh', input_shape=(28,28,1))) model.add(AveragePooling2D()) model.add(Conv2D(filters=16, kernel_size=(3, 3), activation='tanh')) model.add(AveragePooling2D()) model.add(Flatten()) model.add(Dense(units=128, activation='tanh')) model.add(Dense(units=10, activation = 'softmax')) # Print a summary of the model: model.summary()

**TensorFlow Core Application Example**

TensorFlow core applications typically consist of two discrete sections:

**Construction Phase**. Creation of a computational graph consisting of nodes (ops) and tensors (node ‘edges’).**Execution Phase**. The graph is encapsulated in a session and run.

In this example, we construct a basic computational graph and execute it in a session:

# Import the library required in this example: import tensorflow as tf # Class environment in which a graph will be created # and run in a session: tf.compat.v1.Session( target='', graph=None, config=None ) # Disable eager execution (immediate execution of operations # as they are called) in TensorFlow 2.x: tf.compat.v1.disable_eager_execution() # Build a graph. a = tf.constant(7.0) b = tf.constant(11.0) c = a * b # Launch the graph in a session: sess = tf.compat.v1.Session() # Evaluate tensor 'c': print(sess.run(c))

*Figure 1. Launch the graph in a session, and evaluate the tensor:*

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