The abacusnbody.metadata module contains the parameters and states for Abacus simulations like AbacusSummit. One can use this module to query information about simulations without actually downloading or opening any simulation files.

The main entry point is the get_meta(simname, redshift=z) function. Examples and the API are below.

## Examples¶

### Omega(z)¶

import abacusnbody.metadata
print(meta['OmegaNow_m'])  # Omega_M(z=0.1)
print(meta['OmegaNow_DE'])  # Omega_DE(z=0.1)


### Growth Factors in AbacusSummit¶

Growth factors in AbacusSummit are a bit of a special case, because the parameters actually contain a pre-computed table of $$D(z)$$ for all the output epochs and the ICs. This table is a dict called GrowthTable. Since AbacusSummit input power spectra (i.e. CLASS power spectra) are generated at $$z=1$$, one can compute the linear power spectrum at a different epoch via the ratio $$D(z)/D(1)$$:

import abacusnbody.metadata
Dz = meta['GrowthTable']
ztarget = 0.1
linear_pk = input_pk * (Dz[ztarget] / Dz[1.])**2


## Developer Details¶

The metadata is stored in an ASDF file in the abacusnbody/metadata directory. The metadata files are built with scripts/metadata/gather_metadata.py, and then compressed with scripts/metadata/compress.py (using compression on the pickled representation). Internally, the time-independent parameters are separated from the time-varying state values, but the two sets are combined into a single dict that is passed to the user.

## API¶

Retrieve the cosmology and other code parameters associated with an Abacus simulation.

Each set of simulations, like AbacusSummit, has a corresponding repository of metadata. The simulation name will be used to infer which repository to look in.

Get the metadata associated with the given simulation.

Parameters
• simname (str) – The simulation name, like “AbacusSummit_base_ph000_c000”.

• redshift (float or str) – The redshift

Returns

meta – The time-independent parameters and, if redshift is given, the time-dependent state values.

Return type

dict