According to the original paper on the algorithm written by Kenneth O. Stanley and Risto Miikkulainen:

NEAT is a genetic algorithm (GA) for the generation of evolving artificial neural networks. It alters both the weighting parameters and structures of networks, attempting to find a balance between the fitness of evolved solutions and their diversity. It is based on applying three key techniques: tracking genes with history markers to allow crossover among topologies, applying speciation (the evolution of species) to preserve innovations, and developing topologies incrementally from simple initial structures ("complexifying").

My version modifies the following to the algorithm:

1. The artificial neural networks start with only input and output neurons, and every input neuron doesn't have to be linked to an ouput neuron. This allows the algorithm to start with minimal complexity.
2. The neural network isn't recurrent and only allows forward connections.
3. The probabilities of increasing complexity are larger, such as the probability of adding neurons or links.
4. The activation function is the Sigmoid function and there is no activation pertubation (the activation function doesn't change).
5. The fittest neural network from the previous generation advances to the next generation.

These instructions will get you a copy of the algorithm and running on your local machine for development and testing purposes. See deployment for notes on how to deploy the project on a live system.

Your machine needs to be compatible for running Java or C# Code. I recommend using the following IDEs or Engines that I have used the algorithm with:

Java

jMonkeyEngine
NetBeans

C#

Unity Game Engine
Visual Studio

A step by step series of examples that tell you how to get a development env running

Download the zipped version of this repository and choose the C# version or Java version of the algorithm. Then, add the unzipped files to your project directory

Next, adjust the hyperparameters found in Settings.cs or Settings.java if you want to.

public static int NUM_AI = 40; //changes the number of agents to 40

You should now be ready to implement the algorithm in your project.

Explain how to run the automated tests for this system

First, declare and instantiate a reference to the algorithm in your code.

private Ga neatAlgorithm = new Ga(Settings.NUM_AI, 10, 2); //the parameters are the number of ai (Int), the number of input neurons (Int), the number of output neurons (Int)

Then, gather inputs for each of the agents and recieve the outputs using this function. Remember to store fitness scores for each agent.

private List<double> firstAgentOutput = neatAlgorithm.UpdateMember(0, inputs) //the parameters are the index (position) of the agent (Int) and the agent's inputs (List<double>)

Once all of the agents perish and the epoch is over, call the following function to update neural networks with mutations, crossover, and speciation, and then repeat the previous step

neatAlgorithm.Epoch(fitnessList); //the parameter is a list that represents the fitnesses for all of the agents(List<double>, elements must be greater than 0)

You should end with one or multiple neural networks that converge upon the solution. Remember, this may take a while depending on your problem and may be faulty because you are feeding the incorrect inputs to the neural network or misinterpreting the ouputs.

You can deploy this algorithm in your final product. I have had success deploying the algorithm in Unity Game Engine and jMonkeyEngine products, but the algorithm isn't limited to only that.

Here are some example projects that I have used AshayNEAT in:

C#

• Flappy Neat
• Doodle Neat
• Breakout Neat

Java

• NeuroRun

• C# - The programming language used
• Java - The programming language used

• Ashay Parikh - (https://ashayp.com/)

This project is licensed under the Gnu General Public License - see the LICENSE.md file for details

• My Sources
  • The book that went in depth on the code behind the algorithm: AI Techniques for Game Programming by Mat Buckland
  • The research paper that introduced the algorithm: Evolving Neural Networks through Augmenting Topologies by Kenneth O. Stanley and Risto Miikkulainen
• Additional Sources
  • An introductory article: NEAT: An Awesome Approach to NeuroEvolution
  • More resources for those that are interested: The NeuroEvolution of Augmenting Topologies (NEAT) Users Page