The Art of Computational Science

Piet Hut and Jun Makino are two of the leading authorities on n-body simulations. Note the “Alice and Bob” articles on their site which are well worth a read if you’re interested in the underlying physics. ACS was the inspiration for the development of Grav-Sim. The Ruby-based ACS code "world6.rb" was ported to C++ and became the starting point for Grav-Sim development in 2008.

Sverre Aarseth's Institute of Astronomy N-Body and Downloads Page

Sverre Aarseth has dedicated 40 years of his academic life to research on the n-body problem. Much of his focus has been the precise determination of orbits using analytic techniques where possible. The "nbody6" Fortran-based code is regarded by many as the defacto standard. Incorporating some of Sverre's techniques into Grav-Sim will be one of the main challenges for the Grav-Sim development team.

Cosmological Simulations with GADGET

Volker Springel developed the original GADGET cosmological simulation code as part of his PhD thesis. It was subsequently rewritten over the course of several years and is now available for public download as GADGET2. It is written in ANSI C and includes support for gas simulation via "Smoothed Particle Hydrodynamics" or SPH.

The Meta-Institute For Computational Astrophysics

MICA has been setup as a focus for collaboration in the virtual world "Second Life". The OpenSim viewer lets you see small cluster evolution (up to 50 stars) in real time.


Nemo is a comprehensive suite of packages for n-body simulation, maintained by Peter Teuben. It includes the GyrfalcON implementation of Walter Dehnen's O(N) algorithm.


Starlab is a UNIX-based package for n-body simulation. It includes initialisation and analysis routines, the Kira integrator, regularisation of Kepler 2-body orbits, the Seba Stellar Evolution package and integration with the GRAPE supercomputer hardware.



Grav-Sim makes use of gengetopt for parsing command-line arguments.

High Precision Software Directory

This is the source for the QD and ARPREC libraries used in the Fine-Sim simulator.

Shiny Profiler

Shiny is a low overhead, well documented and lightning fast C++ profiler. Grav-Sim can be compiled with the relevant hooks enabled to produce profiler output.


GLUT is a native application that provides easy access to the OpenGL 3D libraries. This is used by the Grav-View viewer.

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PGPlot is a basic plotting library. It was used to produce the orbit error graphs in the Simulation section.

RSA Tools - XY Graph

A number of third-party packages will work with the model and orbit files used by Grav-Sim. One example is the RSA Tools - XY Graph website (although in this case you will need to remove the commas first and replace them with spaces). The 2-body orbit graph in the Models section was produced in this way.

LZO Compression

LZO is a super-fast compression library developed by Marcus Oberhumer. This is not currently used by Grav-Sim, but some experiments have been done with a binary file format in conjunction with LZO.


Bowen Technique

Bowen Technique is a great alternative therapy. For those in Torquay, Torbay or Devon in the UK, Sue Mansfield offers a fantastic service which can be life-changing, depending on your needs. She certainly sorted out my lower back problems. Check out her site at:

Claude Comedy Waiter

Claude is brilliant for garden parties, weddings, festivals and so on. He adds that little extra amusement factor, entertaining his guests with some hilarious gags. He did my 40th birthday party recently and I've not laughed that much in ages. Take a further look at his website:


Telescopes of many varieties.