N-Body Problem Simulation with NEAT AI 🪐🤖

Welcome to the N-Body Problem Simulation with NEAT AI project! This Python-based simulation leverages the power of the NEAT (NeuroEvolution of Augmenting Topologies) algorithm to evolve and simulate the motion of multiple planetary bodies under gravitational forces. This project uses Pygame for visualizations and NEAT-Python for neural network evolution.

Table of Contents

• Overview
• Features
• Installation
• Usage
• Configuration
• Project Structure
• How the AI Works
• Visualization
• License

Overview 📜

This project simulates an N-body gravitational system, where planets are attracted to each other following Newton's law of gravitation. It uses a neural network evolved with NEAT to determine the initial conditions (position and velocity) for each planet. The goal is to evolve stable or interesting systems using fitness-based evaluations.

The core idea is to explore how neural networks can generate stable orbits or controlled planetary systems in a dynamically evolving gravitational context.

Features ✨

• Gravitational simulation of multiple planetary bodies.
• NEAT-based neural network evolution to discover optimal initial conditions.
• Fitness visualization over generations.
• Pygame-based real-time visualization of the simulation.
• Configurable planet count and other simulation parameters.

Installation 🛠️

1. Clone the Repository:

   git clone https://github.com/corzed/n-body-problem-ai.git
   cd n-body-neat-simulation

2. Create a Virtual Environment (Optional but recommended):

   python -m venv env
   source env/bin/activate   # On Windows, use `env\Scripts\activate`

3. Install Dependencies:

   pip install -r requirements.txt

   Make sure you have the following dependencies:

   • pygame
   • neat-python
   • numpy
   • matplotlib

4. Run the Simulation:

   python ai.py

Usage 🚀

After running the script, the program will prompt you to select the number of planets to simulate. You can then choose to start a new training session or load from a saved checkpoint.

Keyboard Controls:

• Up/Down Arrow Keys: Adjust simulation speed.
• Spacebar: Pause or resume the simulation.

Replay Options:

• 'r': Replay a specific genome using its ID.
• 'b': Replay the best genome so far.
• 'p': Plot the fitness history over generations.
• 'q': Quit the program.

Configuration ⚙️

The configuration file for NEAT is automatically generated as config-feedforward.txt and contains adjustable parameters for:

• Population size
• Mutation rates
• Number of inputs/outputs
• Activation functions

Feel free to modify this file as needed to experiment with different evolutionary parameters.

Project Structure 📂

n-body-neat-simulation/
│
├── ai.py                    # Main script for simulation and neural network evolution
├── config-feedforward.txt   # Configuration file for NEAT
├── requirements.txt         # Dependencies
└── README.md                # Project documentation

How the AI Works 🤖🧠

The core algorithm used in this simulation is NEAT (NeuroEvolution of Augmenting Topologies), which evolves a neural network to optimize the initial conditions for the planetary bodies. Here's a deeper look into how this works:

1. Neural Network Structure

The neural network evolved by NEAT takes a simple input vector to generate initial positions and velocities for each planet. The inputs consist of a constant bias (e.g., 1.0) to allow the neural network to generate consistent outputs. The outputs represent:

• X and Y positions of each planet.
• X and Y velocities of each planet.

2. Evolution via NEAT

The NEAT algorithm optimizes the neural network's weights, connections, and even its topology to find the best configuration for creating stable planetary orbits. This is achieved through:

• Population-based search: A population of neural networks is evolved simultaneously.
• Fitness Evaluation: Each neural network's fitness is determined based on how well the simulated planetary system behaves. Stability and lifespan are key indicators of good performance.

3. Fitness Calculation

The fitness function measures the stability and behavior of the planetary system:

• Longevity of the system: The main objective is to evolve networks that can create planetary systems that exist without collisions or escapes for as long as possible.
• Penalties for collisions and escapes: If planets collide or escape beyond a threshold, the simulation terminates early, and penalties are applied to the fitness score.

4. Mutation and Crossover

NEAT applies mutations and crossovers to generate a new population in each generation:

• Mutations involve adding or removing connections between nodes, or adjusting weights and biases.
• Crossover combines successful neural networks to create offspring with a mix of features from both parents.

5. Training and Visualization

The neural networks are trained over multiple generations, with the fitness of the best neural network being plotted over time. You can visualize the results in real time using Pygame.

Visualization 🎨

The simulation is visualized using Pygame, which displays the current planetary system's state. Information such as generation, genome ID, fitness, and simulation speed is displayed in the Pygame window.

License 📜

This project is licensed under the MIT License. See the LICENSE file for details.

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Happy Simulating! 😊🚀🌌