In the sections
StructureFinding, you can
specify the options
output_list which receive an int
and a filename. The
output_list_on enable or not the output list and
output_list is the filename containing the output times. With the file
header, you can choose between writing redshifts, scale factors or times.
Example of file containing with times (in internal units):
# Time 0.5 1.5 3.0 12.5
Example of file with scale factors:
# Scale Factor 0.1 0.2 0.3
Example of file with redshift:
# Redshift 20 15 10 5
If an output list is specified, the basic values for the first
scale_factor_first) and difference
delta_time) are ignored.
When an output list is used SWIFT will not write a “0th” snapshot straight after having read the ICs. Similarly, SWIFT will also not write a snapshot at the end of a simulation unless a snapshot at the final time is specified in the list.
With SWIFT, you can select the particle fields to output in snapshot
using the parameter file. In section
SelectOutput, you can remove
a field by adding a parameter formatted in the following way
field is the name of the field that you
want to remove (e.g.
parttype is the type of
particles that contains this field (e.g.
For a parameter, the only values accepted are 0 (skip this field when
writing) or 1 (default, do not skip this field when writing). By
default all fields are written.
This field is mostly used to remove unnecessary output by listing them
with 0’s. A classic use-case for this feature is a DM-only simulation
(pure n-body) where all particles have the same mass. Outputting the
mass field in the snapshots results in extra i/o time and unnecessary
waste of disk space. The corresponding section of the
parameter file would look like this:
SelectOutput: Masses_DM: 0
You can generate a
yaml file containing all the possible fields
available for a given configuration of SWIFT by running
./swift --output-params output.yml.