N_Body

A multithreaded C++ N-body gravity solver.

Compilation

Move into N_Body and run make. Executables are then found in /bin:

• main - N-body code.
• random - Initializes stars randomly throughout the box.
• lattice - Initializes stars in a cubic lattice. throughout the box.

Usage

main

Usage: main [OPTIONS]
Options:
--threads, -t <num> Number of threads to use (default: maximum available threads)
--parameters, -p <file> Path to parameter file (default: N_Body/parameters.txt)
--initials, -i <file> Path to initial conditions file (default: N_Body/initial_conditions.csv)
--help, -h Display this help message and exit

Parameter file

parameters.txt

• deltaTime: time step (s).
• maxTime: time code runs until (s).
• stepsBetweenSnapshots: number of timesteps between saved snapshots.
• boxSize: size of the periodic box.
• softeningLength: gravitational softening length.

Initial conditions

initial_conditions.csv Each row contains the attributes for each star. The columns are:

• m mass
• x x-coordinate
• y y-coordinate
• z z-coordinate
• vx velocity along x-axis
• vy velocity along y-axis
• vz velocity along z-axis
• ax acceleration along x-axis
• ay acceleration along y-axis
• az acceleration along z-axis

Analysis

Example Python scripts for visualization and analysis in python directory.

3d_plotting.py

Creates an animation of the box in 3d.

2d_plotting.py

Creates an animation of the box in 2d, in the x-y plane.

plotting.py

Creates an animation of the Sun, Earth, Mars, Jupiter system for one Jupiter year.

earth_distance.py

Plots the distance of Earth from the origin.