Pynbody uses a number of different modules behind the scenes to take
care of loading files in different formats. Unfortunately not all of
these have the same capabilities; see below.
| Filetype |
Can load? |
Partial loading? |
Can save? |
Array-level save? |
Notes |
|---|
| Tipsy |
Yes |
Yes |
Yes |
Yes |
|
| Gadget |
Yes |
No [1] |
Yes |
Yes |
|
| GadgetHDF |
Yes |
No [1] |
No |
No |
[2] |
| Ramses |
Yes |
No [1] |
No |
No |
[3], [4] |
| NChilada |
Yes |
Yes |
No |
No |
|
| GrafIC |
Yes |
Yes |
No |
No |
[5] |
| [1] | (1, 2, 3) Currently these modules do not support the standard partial
loading mechanism. However they do allow you to load only certain
CPU outputs. For instance if you wish to load CPU 3 data only, in
Gadget or GadgetHDF, you simply ask to load the
specific file my_snapshot.003 instead of the imaginary file
my_snapshot. In Ramses, you add cpus=[3] to your load
command, e.g. pynbody.load('output_00080', cpus=[3]). |
| [2] | Requires the h5py python module. You can determine whether
you have this by typing import h5py into python. If you don't
get an error, you have it. If you don't have it, see here
<http://www.h5py.org> |
| [3] | Ramses gas cells are loaded and converted into gas particles,
one at the centre of each maximally refined cell. You can ask to
generate the particles at a higher level of refinement by passing
in a maxlevel argument. For example,
pynbody.load('output_00080', maxlevel=10) will place gas
particles at refinement level 10 or (numerically) lower. |
| [4] | Ramses loading is enormously speeded up if you enable the
parallel loading facility, which splits the task of loading the
multiple files and decoding the awkward format across multiple
processes. To do this, you need to install the posix_ipc module which should be
as simple as typing easy_install posix_ipc into your
shell. See also important notes on :ref:`posix_ipc`. |
| [5] | These are initial conditions generated by Bertschinger's
GrafIC or Prunet et al's MPGrafIC. |
The end-user rarely needs to worry about the implementation of
different loaders, as all types of simulations are loaded with
:func:`pynbody.load` and the type is determined automatically.
.. automodule:: pynbody.snapshot.tipsy
.. automodule:: pynbody.snapshot.gadget
.. automodule:: pynbody.snapshot.gadgethdf
.. automodule:: pynbody.snapshot.nchilada
.. automodule:: pynbody.snapshot.ramses
.. automodule:: pynbody.snapshot.grafic