Installation

You need the following python modules installed: numpy, scipy and h5py. To install inspector gadget, checkout the git repository from https://bitbucket.org/abauer/inspector_gadget and run:

python setup.py install

Now the module should be available systemwide.

Usage

Inspector gadget installs two command line tools. arepoinfo gives shows you the header and contents of a snapshot and arepoconvert can convert snapshots to format 3 snapshots. Start them with --help to get a list of options

To use inspector gadget, start ipython and load the module (both modules are the same):

import arepo
# or
import gadget

Loading a Snapshot

The snapshot object provides functionality to load the data into python. Further analysis routines are provided in subclasses such as Simulation, which contains elementary plotting routines.

A snapshot is stored in a Snapshot object:

sn = gadget.Snapshot(“output”, 10)

will load the 10-th snapshot in the folder output. Alternatively the full path of the snapshot file can be specified:

sn.gadget.Snapshot("output/snap_010.hdf5")

Formats 1,2 and 3 have reading support. Writing is however only supported for format 3. See documentation of the snapshot class for details

You can specify which particle types and which fields should be loaded through the parttype and fields options. To load only type 0 and 4 particles and only the masses and velocities, you would use:

sn = gadet.Snapshot('./snapdir_050/snap_050.0.hdf5', parttype=[0,4],  fields =['mass','Velocities'])

If the snapshot is a multipart file, by default only one file is loaded at a time. Use the option combineFiles to load all files at once. Otherwise you can specific the file number using the filenumber option or by providing the correct path. The method nextFile iterates over the individual files of a snapshot.

Working with a Snapshot

To obtain a quick overview what was loaded use:

print(sn)

The header attributes can be accessed via:

sn.header.time
#or
sn.time

The data of a single particle type can be retrieved through:

sn.part0.Masses
#or
sn.part0['Masses']

If you want to access a field for all particles, you may use:

sn.Masses
sn['Masses']

Note: Masses only contains the masses of particle types which have a zero in the Mass Table (sn.header.MassTable). In ipython, tab completion is provided.

You can not exchange these arrays, but have to write into them, i.e.:

sn.Masses = np.ones(2*128**3) #wrong
sn.Masses[:] = 1. #ok

Loading a Subfind Catalog

For subfind catalogs a similar interface is provided. A catalog can be loaded using the Subfind class:

sub = gadget.Subfind('./groups_135/fof_subhalo_tab_135.0.hdf5')

data can be accessed in a similar way:

sub.group.GroupCM
#or
sub.GroupCM

sub.subhalo.SubhaloCM
#or
sub.SubhaloCM

Using filters

While loading a snapshot, the filter option provides a powerful way of loading only a subset of the data. For example only a spherical or rectangular region can be loaded. The following example shows how to load only one friends-of-friends halo:

# select the Halo; sub is a subhalo catalog (see above)
#    you need at least the following fields: fields=['GroupNsubs','SubhaloLenType','GroupLenType']
#    and combineFiles = True
# and load only real star particles
# the Halo filter must be first, then the Stars filter
filter = [gadget.filter.Halo(sub,halo=0), gadget.filter.Stars() ]

# and load the data
sn = gadget.Snapshot('./snapdir_135/snap_135.0.hdf5', parttype=[4], filter=filter, combineFiles=True, verbose=True)

Simple analysis and plotting routines

The Snapshot class provides only loading functionality. All methods of that class load the data as it is (except for optional conversion to double precision). Additional data manipulation and analysis functionality is provided through subclasses. The Simulation subclass contains a few basic analysis and plotting methods:

sn = gadget.Simulation("snap_003.hdf5")

# A slice through the Voronoi mesh
sn.plot_Aslice("rho")

# A slice through an AMR mesh
sn.plot_AMRslice("rho")

#obtaining a radial profile
sn.get_radprof("u")

#plotting the profile right away
sn.plot_radprof("u")

Initial Conditions

Initial conditions can be created using the ICs class. An empty snapshot is created, which can be filled and written to a file. All default fields are present. Additional fields can be added using the addField method:

#create ICS with 128**3 gas cells and 128**3 DM particles
ics = gadget.ICs("ics.hdf5", [128**3,128**3])

#write into an array
ics.ids[:] = np.arange(2*128**3) + 1

ics.write()