ChaNGa reads in initial conditions, (i.e. the initial positions, velocities, masses, etc. of all the particles) from a binary file in either Tipsy or N-Chilada format. The name of this file is specified by the achInFile parameter in the parameter file (or -I argument on the command line). See the File Formats page for the structure of this file.

There are a number of packages to generate such files. Some are listed here categorized by their area of science.

Cosmology

MUSIC creates zoom-in initial conditions for simulating the formation of galaxies in a cosmological context.

Grafic++ (Doug Potter) is a MPI/C++ code to generate initial conditions for cosmological simulations using multiscale gaussian random fields, based on Edmund Bertschinger's GRAFIC-2 package.

PKDGRAV3 (Potter and Stadel) is a high performance N-body treecode for self-gravitating astrophysical simulations that can also produce cosmological initial conditions.

Isolated Halos

PyICs (Jakob Herpich) generates dark matter halos in dynamical equilibrium which host a rotating gas sphere.

ICInG (Michael Tremmel) creates initial conditions gor an isolated cosmological collapsing halo of dark matter and gas.

Protoplanetary Disks

Diskpy (Isaac Backus) creates initial conditions for protoplanetary disk simulations.

Planets

Balic (Reinhardt & Stadel 2017) creates particle representations of planets for SPH simulations.

Computer Science

If you need random data, e.g., to test scaling, see the testdata directory of the ChaNGa distribution.