GADGET computes gravitational forces with a hierarchical tree algorithm (optionally in combination with a particle-mesh scheme for long-range gravitational forces) and represents fluids by means of smoothed particle hydrodynamics (SPH). The code can be used for studies of isolated systems, or for simulations that include the cosmological expansion of space, both with or without periodic boundary conditions. In all these types of simulations, GADGET follows the evolution of a self-gravitating collisionless N-body system, and allows gas dynamics to be optionally included. Both the force computation and the time stepping of GADGET are fully adaptive, with a dynamic range which is, in principle, unlimited.
GADGET can therefore be used to address a wide array of astrophysically interesting problems, ranging from colliding and merging galaxies, to the formation of large-scale structure in the Universe. With the inclusion of additional physical processes such as radiative cooling and heating, GADGET can also be used to study the dynamics of the gaseous intergalactic medium, or to address star formation and its regulation by feedback processes.
|Hierarchical multipole expansion (based on a geometrical oct-tree) for gravitational forces.|
|Optional TreePM method, where the tree
is used for short-range gravitational forces only while long-range
are computed with a FFT-based particle-mesh (PM) scheme. A second PM
layer can be placed on a high-resolution region in 'zoom'-simulations.
boundary conditions, either by means of the Ewald summation technique
or based on the FFT algorithm used in the TreePM scheme. Simulations
that only follow gas dynamics without self-gravity can be run in
periodic boxes with arbitrary aspect ratios,
and also in 2D, if desired.
|Smoothed particle hydrodynamics with
adaptive smoothing lengths and a novel entropy conserving formulation
parameterisation of the artificial viscosity, as
suggested by Monaghan.
|Individual timesteps for
all particles. In the TreePM scheme, long-range and short-range forces
are integrated with different timesteps.
|Work-load balanced domain decomposition and dynamic tree updates.|
|Efficient cell-opening criteria for the gravitational tree-walk.|
|Support for parallel I/O and a number
of different output formats, including the HDF5 format.
|Flexible control of all code options by a free-format parameterfile.|
|Portable, well documented and easily extendible code, relying only on standard ANSI C language features and MPI-1.0 communication calls.|
|High raw computational speed and
comparatively low memory consumption. In particular, significant
improvements in resource consumption compared with GADGET-1 have been achieved.
|The code may be run on an arbitrary number of processors, with a restriction to powers of two. It may also be run on a single CPU in serial mode.|
|Fast method for the generation of a gravitational `glass'.|
|SPH simulations can be run in periodic boxes of arbitrary aspect ratio, or in 2D, if desired.|
There have also been older versions of the code that supported the special-purpose hardware GRAPE, in the form of GRAPE-3 and GRAPE-6. However, this functionality is not included in the current version at the moment.
2001-2003, GADGET-2 was created. The new code forms a nearly complete
of GADGET-1, including a replacement of all core algorithms with
new methods. The most important changes lie in a new time integration
model, a new tree-code module, a new communication scheme for
gravitational and SPH forces, a new domain decomposition strategy, a
SPH formulation based on entropy as indepedent variable, and finally,
addition of the TreePM functionality.
Current work on GADGET-3 is done by a number of people besides Volker Springel. A public release of this code has not happened yet, but is foreseen for the not too distant future.
|1 May 2005:||Version 2.0 of GADGET released.
|1 June 2001:||GADGET updated to version 1.1|
|16 March 2000:||The initial distribution contained a wrong version of the file `forcetree.c' of the serial version of GADGET. Please download the serial code again!|
|15 March 2000:||Version 1.0 of GADGET released.|
|1 January 2000:||GADGET's Y2K compliance established.|
Please use the commands `gunzip gadget-2.0.7.tar.gz' and `tar -xvf gadget-2.0.7.tar' to unpack the files. You will obtain a directory `Gadget-2.0.7/' , and various subdirectories containing the actual source code, the code documentation, as well as a number of simulation examples and very basic analysis scripts. Please refer to the README file, and GADGET's User's Guide for further directions about installation and usage. A brief guide to parameters in the Makefile and the parameterfile, as well as a cross-referenced source code documentation is accessible with a web-browser in the `html/'-subdirectory (open the `index.html' file). Note that the large size of the download is caused by the included example initial conditions.
gadget-2.0.7.tar.gz (~21.5 MB)
This code is suitable for creating cosmological initial conditions based on the Zeldovich approximation, in a format directly compatible with GADGET. This IC generator has been written several years back (~2003) by Volker Springel. The code is MPI-parallel and suitable for creating very large initial conditions, if desired. Please consult to the enclosed README file for instructions on how to use it.
n-genic.tar.gz (~0.03 MB)
|A pair of colliding disk galaxies (collisionless)|
|A spherical collapse of a self-gravitating sphere of gas|
|Cosmological formation of a cluster of galaxies (collisionless, vacuum boundaries)|
|Cosmological structure formation in a periodic box with adiabatic gas physics|
Please refer to the User's Guide for detailed information on how you can run these examples with GADGET. We also provide a few IDL-scripts for a simple analysis of some of GADGET's output.
|Colliding disk galaxies|
|Hydrodynamical simulations of cosmic structure formation|
|Merging galaxies with quasar feedback|
|Constrained Realizations of the Local Universe|
|High-resolution simulations of a cluster of galaxies|
We here just provide a few examples of these animations in the form of heavily size-reduced and compressed movies in the MPEG1 or MPEG4 formats. Playing these movies in proper quality requires a reasonably fast computer. Some of the movies are encoded using "divx", a flavour of the MPEG4 movie compression algorithms. On Linux computers, you can use the mplayer application to play them, on Apple or Windows computers you may have to install the free version of the divx-codec first.
The Local Universe (Constrained Realization project) (7.4 MB)Further and more current visual material can be obtained from the web-pages of the Theoretical Astrophysics (TAP) group at the Heidelberg Insitute for Theoretical Studies (HITS), or the data visualization web-site of MPA's galaxy formation group.
Two colliding and merging spiral galaxies (4.8 MB)
Dark matter substructure in a cluster of galaxies (7.5 MB)
A forming cluster of galaxies (112 MB, divx)
Merging galaxies with supermassive black holes (22 MB, divx)
A zoom into the Millennium Simulation (49 MB, divx)
We here provide a few links to software by other people that can be used together with GADGET. Note that this list is likely not complete, and does not mean that we specifically endorse a certain type of software.
Visualization software SPLASH (by Daniel Price)
Visualization software IRFIT (by Nick Gnedin)
| Prof. Dr. Volker Springel
Heidelberg Insitute for Theoretical Studies
|Zentrum für Astronomie, University of Heidelberg