Artificial Neural Networks with Net# in Azure ML Studio

The ideas for neural networks go back to the 1940s. The essential concept is that a network of artificial neurons built out of interconnected threshold switches can learn to recognize patterns in the same way that an animal brain and nervous system does.

Though the name “neural network” gives an idea of a ‘black box’ type predictive operation; ANN is a set of mathematical operations.

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As the name implies by itself; neural network is a structural ‘network’. The nodes of the neural network are organized in layers and the nodes are connected with each other with edges. The edges are directional and they are weighted.

Azure Machine Learning Studio comes with pre-built neural network modules that can easily use for predictive analytics.

NN models

Pre-built neural networks in AML Studio  

Multiclass Neural Network Module –

Used for multiclass classification problems. The number of hidden nodes, the learning date, number of learning iterations and many parameters can be changed easily by changing the module properties.

Two-Class Neural Network –

Ideal for binary classification problems. Same as the Multiclass neural network module, the properties of the neural network can be changed by the module properties.

Neural Network regression –

This is a supervised machine learning method that can be used to predict a numerical value.

These simple pre-built modules can be added to your ML experiment with just a drag and drop and change the parameters by changing the module properties. What you going to do if you want to implement a complex neural network architecture? Or to create a deep neural network with more hidden layers?

AzureML Studio comes handy here with providing you the ability to define the hidden layer/layers of the ANN with a script. Net# scripting language provide the ability to define almost any neural network architecture in an easy to read format.

Net# scripting language is able to

  • Create hidden layers and control the number of nodes in each layer.
  • Specify how layers are to be connected to each other.
  • Define special connectivity structures, such as convolutions and weight sharing bundles.
  • Specify different activation functions.

In Azure Machine Learning, you can add the Net# scripts by choosing ‘Custom definition script’ in Hidden layer specification property. By default, it would set to the fully connected case.

properties

Net# lexical is more similar to C#. The structure of a Net# script has four main sections.

  1. Constant declaration (Optional) – Define values used elsewhere in the neural network definition
  2. Layer declaration – The input, hidden and output layers are defined with the layer dimensions. The layer declaration for hidden or output layer can include the output function.
  3. Connection declaration – You can define connection bundles (Full, Filtered, Convolutional, Pooling, Response normalization) – Full connection bundle is the default configuration.
  4. Share declaration (Optional) – Defining multiple bundles with shared weights.

This is a simple neural network defined by a Net# script to perform a binary classification. You can customize the number of hidden neurons and the activation functions and see how the accuracy of the model variate.

<!– HTML generated using hilite.me –>

//A simple neural network definition
//auto keyword allows the ANN to automatically include all feature columns in the input examples
//input layer named Data
input Data auto;

//Hidden layer named "H" including 200 nodes
hidden H [200] from Data all;

//output layer named "Out" including 2 nodes (binary classification problem) 
//Sigmoid activation function has been used.
output Out [2] sigmoid from H all;

For more insides here’s the resources – https://docs.microsoft.com/en-us/azure/machine-learning/studio/azure-ml-netsharp-reference-guide#overview

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