nbodykit.io.gadget¶

Classes

class nbodykit.io.gadget.Gadget1File(path, columndefs=[('Position', ('auto', 3), 'all'), ('GadgetVelocity', ('auto', 3), 'all'), ('ID', 'auto', 'all'), ('Mass', 'auto', None), ('InternalEnergy', 'auto', (0,)), ('Density', 'auto', (0,)), ('SmoothingLength', 'auto', (0,))], hdtype=[('Npart', ('u4', 6)), ('Massarr', ('f8', 6)), ('Time', 'f8'), ('Redshift', 'f8'), ('FlagSfr', 'i4'), ('FlagFeedback', 'i4'), ('Nall', ('u4', 6)), ('FlagCooling', 'i4'), ('NumFiles', 'i4'), ('BoxSize', 'f8'), ('Omega0', 'f8'), ('OmegaLambda', 'f8'), ('HubbleParam', 'f8'), ('FlagAge', 'i4'), ('FlagMetals', 'i4'), ('NallHW', ('u4', 6)), ('flag_entr_ics', 'i4')], ptype=1)[source]¶

Read snapshot binary files from Volkers Gadget 1/2/3 simulations.

These files are stored column-wise with a format, with a header of size 28 bytes to begin the file.

The columns are:

• Position : ‘f4’, ‘f8’ precision

  the position data, usually in Kpc/h units.

• GadgetVelocity : ‘f4’, ‘f8’ precision

  the Gadget 1 velocity, sqrt(a)**-1 v_p. in km/s

• ID : ‘i8’/’i4’ precision

  integers specfiying the particle ID

Parameters:	path (str) – the path to the binary file to load columndefs (list) – a list of triplets (columnname, element_dtype, particle_types) ptype (int) – type of particle of interest. hdtype (list, dtype) – dtype of the header; must define Massarr and Npart

References

https://wwwmpa.mpa-garching.mpg.de/gadget/users-guide.pdf

Attributes

columns	A list of the names of the columns in the file.
dtype	A numpy.dtype object holding the data types of each column in the file.
ncol	The number of data columns in the file.
shape	The shape of the file, which defaults to (size, )
size	The size of the file, i.e., number of rows

Methods

asarray()	Return a view of the file, where the fields of the
get_dask(column[, blocksize])	Return the specified column as a dask array, which
keys()	Aliased function to return columns
read(columns, start, stop[, step])	Read the specified column(s) over the given range

read(columns, start, stop, step=1)[source]¶

Read the specified column(s) over the given range

‘start’ and ‘stop’ should be between 0 and size, which is the total size of the binary file (in particles)

Parameters:	columns (str, list of str) – the name of the column(s) to return start (int) – the row integer to start reading at stop (int) – the row integer to stop reading at step (int, optional) – the step size to use when reading; default is 1
Returns:	structured array holding the requested columns over the specified range of rows
Return type:	numpy.array