.. Command line options
   Matthieu Schaller, 21st October 2018

.. _cmdline-options:

Command line options
====================

SWIFT requires a number of runtime options to run and get any sensible output.
For instance, just running the ``swift`` binary will not use any SPH or gravity;
the particles will just sit still!

Below is a list of the command line options and when they should be used. The same list
can be found by typing ``./swift -h``:

.. code-block:: none


    -h, --help                        show this help message and exit

  Simulation options:

    -b, --feedback                    Run with stars feedback.
    -c, --cosmology                   Run with cosmological time integration.
    --temperature                     Run with temperature calculation.
    -C, --cooling                     Run with cooling (also switches on --temperature).
    -D, --drift-all                   Always drift all particles even the ones
                                      far from active particles. This emulates
                                      Gadget-[23] and GIZMO's default behaviours.
    -F, --star-formation              Run with star formation.
    -g, --external-gravity            Run with an external gravitational potential.
    -G, --self-gravity                Run with self-gravity.
    -M, --multipole-reconstruction    Reconstruct the multipoles every time-step.
    -s, --hydro                       Run with hydrodynamics.
    -S, --stars                       Run with stars.
    -B, --black-holes                 Run with black holes.
    -k, --sinks                       Run with sink particles.
    -u, --fof                         Run Friends-of-Friends algorithm to
                                      perform black hole seeding.
    --lightcone                       Generate lightcone outputs.
    -x, --velociraptor                Run with structure finding.
    --line-of-sight                   Run with line-of-sight outputs.
    --limiter                         Run with time-step limiter.
    --sync                            Run with time-step synchronization
                                      of particles hit by feedback events.
    --csds                            Run with the Continuous Simulation Data
                                      Stream (CSDS).
    -R, --radiation                   Run with radiative transfer.
    --power                           Run with power spectrum outputs.

  Simulation meta-options:

    --quick-lyman-alpha               Run with all the options needed for the
                                      quick Lyman-alpha model. This is equivalent
                                      to --hydro --self-gravity --stars --star-formation
                                      --cooling.
    --eagle                           Run with all the options needed for the
                                      EAGLE model. This is equivalent to --hydro
                                      --limiter --sync --self-gravity --stars
                                      --star-formation --cooling --feedback
                                      --black-holes --fof.
    --gear                            Run with all the options needed for the
                                      GEAR model. This is equivalent to --hydro
                                      --limiter --sync --self-gravity --stars
                                      --star-formation --cooling --feedback.
    --agora                           Run with all the options needed for the
                                      AGORA model. This is equivalent to --hydro
                                      --limiter --sync --self-gravity --stars
                                      --star-formation --cooling --feedback.

  Control options:

    -a, --pin                         Pin runners using processor affinity.
    --nointerleave                    Do not interleave memory allocations across
                                      NUMA regions.
    -d, --dry-run                     Dry run. Read the parameter file, allocates
                                      memory but does not read the particles
                                      from ICs. Exits before the start of time
                                      integration. Checks the validity of
                                      parameters and IC files as well as memory
                                      limits.
    --no-io                           Skip writing snapshots and restart files.
    -e, --fpe                         Enable floating-point exceptions (debugging
                                      mode).
    -f, --cpu-frequency=<str>         Overwrite the CPU frequency (Hz) to be
                                      used for time measurements.
    -n, --steps=<int>                 Execute a fixed number of time steps.
                                      When unset use the time_end parameter
                                      to stop.
    -o, --output-params=<str>         Generate a parameter file with the options
                                      for selecting the output fields.
    -P, --param=<str>                 Set parameter value, overiding the value
                                      read from the parameter file. Can be used
                                      more than once {sec:par:value}.
    -r, --restart                     Continue using restart files.
    -t, --threads=<int>               The number of task threads to use on each
                                      MPI rank. Defaults to 1 if not specified.
    --pool-threads=<int>              The number of threads to use on each MPI
                                      rank for the threadpool operations.
                                      Defaults to the numbers of task threads
                                      if not specified.
    -T, --timers=<int>                Print timers every time-step.
    -v, --verbose=<int>               Run in verbose mode, in MPI mode 2 outputs
                                      from all ranks.
    -y, --task-dumps=<int>            Time-step frequency at which task graphs
                                      are dumped.
    --cell-dumps=<int>                Time-step frequency at which cell graphs
                                      are dumped.
    -Y, --threadpool-dumps=<int>      Time-step frequency at which threadpool
                                      tasks are dumped.
    --dump-tasks-threshold=<flt>      Fraction of the total step's time spent
                                      in a task to trigger a dump of the task plot
                                      on this step

See the file examples/parameter_example.yml for an example of parameter file.

