gadget-snapshot-reader (GSR)

GADGET is a cosmological SPH and N-body code, written by Volker Springel.

Since this code is widely used by the cosmological community, and considering the growth of Python use among scientist, Patrick Brem decided to write a simple script to read the snapshot and be able to access the data.

I decided to improve his code, and add more features, to provide a nice/simple module to deal with the GADGET binary snapshots.

Be aware, the project is still under development.

Installation

To use this module, you can install is using the setup.py.

    python setup.py install --user

Examples

You can visit the examples directory to see a couple of ways to use GSR.

Usage

For a simple transformation from the gadget-binary file to ascii, you can do the following:

from gsr import *

snap = Snapshot(filename)
snap.to_ascii()

Every ascii file is generated using the following order:

| id | mass | posx | posy | posz | velx | vely | velz | u | rho |

It is possible to process more parameters, just enabling them in the constructor call, for example:

• snap = Snapshot(filename, enable_potential = True)

Extra options are:

• enable_potential
• enable_accelerations
• enable_entropy_production
• enable_timesteps
• enable_density
• enable_smoothing_lenght

If you want to print certain information from the snapshot by type:

particle_type = 5  # From GADGET, only 0, 1, 2, 3, 4, 5
snap.print_data_by_type(particle_type)

To use the data from the snapshot, it is possible to get a list with all the information of a particle type:

particle_type = 5
data = snap.get_data_by_type(particle_type)

which will return a dictionary with the following structure:

{'id':[id0, id1, ...],'mass':[mass0, mass1, ...], 'pos':[[pos0x, pos0y, pos0z], [pos1x, pos1y, pos2z]], 'vel':[[vel0x, vel0y, vel0z], [vel1x, vel1y, vel1z], ...]]

if the requested type is 0 (Gas) the dictionary will also include the Internal energy u and the Density rho.

Feedback

Since the project is still under development, a lot of feature are missing, and will be really nice if you can collaborate, asking for a new functionallity or even submitting a pull request to improve the code.