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# Parameterfile
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The parameter-file, often named param.txt, is a file containing run-time
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options for AREPO. These include things like the input and output directory,
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maximum runtimes, memory limits and all kind of freely choosable simulaiton
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and model parameters. In general, the code will output an error message if
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there are either missing paramters for the given configuration AREPO was
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compiled with, or if there are obsolete paramters. The latter can be
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deactivated by setting the compile-time flag ``ALLOWEXTRAPARAMS``.
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Unlike changing Config.sh, changing the parameters does not require
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re-compilation of the code.
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Initial conditions
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==================
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**InitCondFile**
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The filename of the initial conditions file. Can be a relative or absolute
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path. The ICs can be distributed in one or more files, as with snapshots.
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If using ICs with multiple files, only the basename without the trailing
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".n" should be specified here. Similarly, the ".hdf5"
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extension can be omitted, and the code will automatically append it for
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``ICFormat=3``. If a restart from a snapshot with the "2" option is desired,
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one needs to specify the snapshot file here.
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-----
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**ICFormat**
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The file format of the initial conditions. Currently, three different formats
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are supported, selected by one of the choices "1", "2", or "3". Format "1"
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is the traditional fortran-style unformatted format familiar from GADGET.
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Format "2" is a variant of this format, where each block of data is
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preceeded by a 4-character block-identifier. Finally, format "3" selects the
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HDF-5 format.
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-----
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**InitGasTemp**
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This sets the initial gas temperature (assuming either a mean molecular
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weight corresponding to full ionization or full neutrality, depending on
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whether the temperature is above or below 10^4 K) in Kelvin when initial
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conditions are read. However, the gas temperature is only set to a certain
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temperature if ``InitGasTemp>0``, and if the temperature of the gas particles
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in the initial conditions file is zero, otherwise the initial gas
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temperature is left at the value stored in the IC file.
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-----
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**MinimumDensityOnStartUp**
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This sets a lower limit to the density of gas cells after reading in. All
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cells that have a lower density are set to this value.
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-----
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**MHDSeedDir**
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``MHD_SEEDFIELD``
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Direction of the uniform B field that is set before starting the simulation.
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The direction is encoded by sum(2^k), where k is the index of direciton
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(0, 1, 2 for x, y, z, respectively). E.g. 3 is a diagonal field in
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the xy plane, parallel to the z axis. This allows only orientations along
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coordinate axis, perpendicular to it or diagonal. Note that the equations of
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ideal MHD do not change if the field is reversed.
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-----
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**MHDSeedValue**
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``MHD_SEEDFIELD``
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Value of the uniform initial magnetic field in comoving Gauss.
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-----
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**TileICsFactor**
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``TILE_ICS``
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Factor by which the ICs are dublicated in each dimension. Should be an
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integer.
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-----
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**GridSize**
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``ADDBACKGROUNDGRID``
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Initial guess of grid size for ``ADDBACKGROUNDGRID``. The input will be
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rounded to the nearest power of two.
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-----
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Output file names and formats
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=============================
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**OutputDir**
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Pathname of the output directory of the code. Can be a relative or absolute
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path. Path must exist.
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-----
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**SnapshotFileBase**
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Basename of snapshot files produced by the code. e.g. ``snap`` for output files
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``snap_000.hdf5`` etc.
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-----
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**NumFilesPerSnapshot**
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The number of separate files requested for each snapshot dump. Each file of
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the snapshot will hold the data of one or several processors, up to all of
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them. ``NumFilesPerSnapshot`` must hence lie between 1 and the number of
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processors used. Distributing a snapshot onto several files can be done
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in parallel and may lead to much better I/O performance, depending on the
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hardware configuration. It can also help to avoid problems due to big
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files for large simulations. Note that initial conditions may also
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be distributed into several files, the number of which is automatically
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recognised by the code and does not have to be equal to
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``NumFilesPerSnapshot`` (it may also be larger than the number of
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processors).
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-----
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**OutputListOn**
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If set to "1", the code tries to read a list of desired output times from the
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file given in ``OutputListFilename``. Otherwise, output times are generated
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equally spaced from the values assigned from ``TimeOfFirstSnapshot`` onwards
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with spacing ``TimeBetSnapshot``.
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-----
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**OutputListFilename**
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File with a list of the desired output times. Can be specified with a
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relative or absolute path.
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-----
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**SnapFormat**
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Similar to ``ICFormat``, this parameter selects the file-format of snapshot
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dumps produced by the code. 1 and 2 are two binary formats, identical to
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the ones in GADGET. 3 is an HDF5 output, which is recommended unless
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there are good reasons not to use it.
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-----
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**NumFilesWrittenInParallel**
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The number of files the code may read or write simultaneously when writing
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or reading snapshot/restart files. If the value of this parameter is larger
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than the number of processors, it is capped by that. This parameter is only
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important for very large runs, where the file-system can be significantly
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affected by too many tasks writing (restart files) at the same time.
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-----
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**AlternativeOutputDir**
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``TOLERATE_WRITE_ERROR``
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Path name of an alternative output directory which is used in case output
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to OutputDir fails.
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-----
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Output frequency
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================
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**CpuTimeBetRestartFile**
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The value specfied here gives the time in seconds the code will run before it
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writes regularly produced restart files. This can be useful to protect
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against unexpected interruptions (for example due to a hardware problem) of
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a simulation, particularly if it is run for a long time. It is then possible
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to resume a simulation from the last restart file, reducing the potential
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loss to the elapsed CPU-time since this was produced.
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-----
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**TimeBetSnapshot**
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The time interval in code units between two subsequent snapshot files in
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case a file with output times is not specified. For cosmological
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simulations, this is a multiplicative factor applied to the time of the
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last snapshot, such that the snapshots will have a constant logarithmic
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spacing in the scale factor. Otherwise, the parameter is an additive
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constant that gives the linear spacing between snapshot times.
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-----
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**TimeBetStatistics**
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The code can be asked to measure the total kinetic, thermal, and potential
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energy in regular intervals, and to write the results to the file given in
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``energy.txt``. The time interval between two such measurements
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is given by this parameter, in an analogous way as with ``TimeBetSnapshot``.
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Note that the compile time option ``EVALPOTENTIAL`` needs to be activated to
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obtain a measurement of the gravitational potential energy.
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-----
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**TimeOfFirstSnapshot**
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The time of the first desired snapshot file in code units in case a file with
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output times is not specified. For cosmological simulations, the value given
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here is the scale factor of the first desired output.
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-----
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**FlushCpuTimeDiff**
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``REDUCE_FLUSH``
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Time interval (in seconds) for flush calls on all log-files (i.e. save
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write buffer to disk). In case ``Reduce_Flush`` is not set, this is done
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during every sync-point.
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-----
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CPU-time limit and restarts
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===========================
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**TimeLimitCPU**
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CPU-time limit for the present submission of the code. If 85 percent of this
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time have been reached at the end of a timestep, the code terminates itself
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and produces restart files. The extra 15% is used to guarantee that there is
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enough time to safely finish the current time step and write the restart
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files. This CPU time refers to the wall-lock time on a single
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processor only.
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-----
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**ResubmitOn**
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If set to "1", the code will try to resubmit itself to the queuing system
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when an interruption of the run due to the CPU-time limit occurs. The
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resubmission itself is done by executing the program/script given with
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``ResubmitCommand``.
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-----
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**ResubmitCommand**
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The name of a script file or program that is executed for automatic
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resubmission of the job to the queuing system. Note that the file given here
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needs to be executable.
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-----
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Memory allocation
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=================
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**MaxMemSize**
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The memory allocate per MPI task, in megabytes. A contiguous memory arena of
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this total size is allocated at startup, and then partitioned internally
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within AREPO for memory allocation and deallocation requests. Can generally
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be set to ~95% of the total available, e.g. (memory per node / number of MPI
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tasks per node), to leave room for operating system tasks and MPI buffers.
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This value can be changed on a restart to increase the amount of memory
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available to each task.
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-----
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Simulated time and spatial extent
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=================================
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**BoxSize**
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The boxsize for the simulation, in internal code units.
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All particles and gas cells in the ICs must have Coordinates
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within the range ``[0,BoxSize]`` in each dimension. The only exception from
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this is for collisionless particles in a tree-only gravity mode (no
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``PMGRID``) and ``GRAVITY_NONPERIODIC``.
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-----
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**PeriodicBoundariesOn**
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If set to "1", periodic boundary conditions are assumed, with a cubical
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box-size of side-length ``BoxSize``. Particle coordinates are expected to
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be in the range ``[0,BoxSize[``. Can only be set to zero if
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``GRAVITY_NOT_PERIODIC`` is set. Note: refers to gravity only! Hydrodynamic
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boundary conditions are handled by ``REFLECTIVE_X``,
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``REFLECTIVE_Y`` and ``REFLECTIVE_Z`` in ``Config.sh``
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-----
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**TimeBegin**
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This sets the starting time of a simulation when the code is started from
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initial conditions in internal code units. For cosmological integrations,
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the value specified here is taken as the initial scale factor.
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-----
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**TimeMax**
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This sets the final time for the simulation. The code normally tries to run
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until this time is reached. For cosmological integrations, the value given
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here is the final scale factor.
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-----
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Cosmological parameters
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=======================
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**ComovingIntegrationOn**
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If set to "0", the code assumes plain Newtonian physics, with time,
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positions, velocities, and masses measured in the internal system of units.
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If set to "1", the code assumes that a cosmological integration in comoving
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coordinates should be carried out, assuming an expanding universe described
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by the 'Cosmological parameters' below. In a cosmological integration, the
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time variable is the scale factor.
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-----
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**Omega0**
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Gives the total matter density in units of the
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critical density at z=0 for cosmological simulations. Relevant for comoving
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integration and halo/subhalo finder
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-----
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**OmegaBaryon**
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Gives the baryon density in units of the critical
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densty at z=0 for cosmological simulations. Relevant for comoving
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integration, halo/subhalo finder and star formation model.
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-----
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**OmegaLambda**
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Gives the vacuum energy density (cosmological
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constant) at z=0 for cosmological simulations. Relevant for comoving
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integration and halo/subhalo finder
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-----
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**HubbleParam**
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This gives the Hubble constant ("little h") at z=0 in units of
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100 km/sec/Mpc. Note that this parameter has been basically absorbed into
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the definition of the internal code units, such that for gravitational
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dynamics and adiabatic gas dynamics the actual value assigned for
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``HubbleParam`` is not used by the code. Only used when conversions to
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physical cgs units are required (e.g. for radiative cooling physics).
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In other cases, use 1.0.
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-----
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System of units
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===============
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**UnitVelocity_in_cm_per_s**
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This sets the internal velocity unit in **cm/sec**. For example, the
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choice of ``1e5`` sets the velocity unit to 1.0 *km/sec*.
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Note that the specification of ``UnitLength_in_cm``, ``UnitMass_in_g``, and
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``UnitVelocity_in_cm_per_s`` also determines the internal unit of time.
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-----
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**UnitLength_in_cm**
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This sets the internal length unit in **cm/h**, where H_0 = 100 h km/sec/Mpc.
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For example, the choice of ``3.085678e21`` sets the length unit to
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`1.0 kpc/h`.
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-----
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**UnitMass_in_g**
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This sets the internal mass unit in **g/h**, where H_0 = 100 h km/sec/Mpc.
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For example, the choice of ``1.989e43`` sets the mass unit to
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`10^10 Msun/h`.
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-----
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**GravityConstantInternal**
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The numerical value of the gravitational constant G in internal units depends
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on the system of units you choose. For example, for the choices above,
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`G=43007.1` in internal units. For ``GravityConstantInternal=0``, the code
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calculates the value corresponding to the physical value of G automatically.
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However, you might want to set G yourself. For example, by specifying:
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``GravityConstantInternal=1``, ``UnitLength_in_cm=1``, ``UnitMass_in_g=1``,
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and ``UnitVelocity_in_cm_per_s=1``, one obtains a *natural* system of units.
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Note that the code will nevertheless try to use the *correct* value of the
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Hubble constant in this case, so you should not set
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``GravityConstantInternal`` in cosmological integrations.
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-----
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Gravitational force accuracy
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============================
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**TypeOfOpeningCriterion**
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This selects the type of cell-opening criterion used in the tree walks. A
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value of "1" selects the relative opening criterion.
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*Required value: 1* (only implemented option).
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-----
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**ErrTolTheta**
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If the relative opening criterion is used, a first force estimate is
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computed using the Barnes-Hut tree algorithm, which is then recomputed
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with the relative opening criterion.
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|
-----
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**ErrTolForceAcc**
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The accuracy parameter for the relative opening criterion for the tree walk.
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-----
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Time integration accuracy
|
|
|
=========================
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**TypeOfTimestepCriterion**
|
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|
This parameter can in principle be used to select different kinds of
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timestep criteria for gravitational dynamics. However, AREPO presently only
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supports the criterion "0".
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|
-----
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|
**ErrTolIntAccuracy**
|
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|
|
This dimensionless parameter controls the accuracy of the timestep criterion
|
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|
selected by ``TypeOfTimestepCriterion``. It is the variable ``eta``,
|
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|
where the cosmological timestep for collisionless particles scales as
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`dt ~ eta^0.5`.
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|
|
-----
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**MaxSizeTimestep**
|
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|
|
This gives the maximum timestep a particle may take. This should be set to a
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sensible value in order to protect against too large timesteps for particles
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|
with very small acceleration. For cosmological simulations, the parameter
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|
given here is the maximum allowed step in the logarithm of the expansion
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|
factor. For comoving runs, this is in units of ``dln(a)``.
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|
-----
|
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**MinSizeTimestep**
|
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|
|
If a particle requests a timestep smaller than the value specified here, the
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code will normally terminate with a warning message. If compiled with the
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|
``NOSTOP_WHEN_BELOW_MINTIMESTEP`` option, the code will instead force the
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|
|
timesteps to be at least as large as ``MinSizeTimestep``.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**CourantFac**
|
|
|
|
|
|
This sets the value of the Courant parameter used in the determination of the
|
|
|
hydrodynamical timestep of gas cells. The hydrodynamical timestep is this
|
|
|
value times the Courant–Friedrichs–Lewy (CFL) condition calculated for each
|
|
|
cell.
|
|
|
|
|
|
-----
|
|
|
|
|
|
|
|
|
Domain decomposition
|
|
|
====================
|
|
|
|
|
|
**ActivePartFracForNewDomainDecomp**
|
|
|
|
|
|
Fraction of particles that need to be at least active in order to trigger a
|
|
|
new domain decomposition at a sync-point. All sync-points where fewer
|
|
|
particles are active will not perform a domain decomposition.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**MultipleDomains**
|
|
|
|
|
|
Number of domains per MPI task. Consequently, the domain decomposition will
|
|
|
cut computational box in ``MultipleDomains`` times number of tasks chunks.
|
|
|
Too few of them will lead to cpu load and memory inbalances, too many to more
|
|
|
MPI communication as there are more domain boundaries.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**TopNodeFactor**
|
|
|
|
|
|
Determines how deep the top-level tree is extended (1.0: only as far as
|
|
|
necessary to split domain in the required number of chunks). The higher this
|
|
|
factor is, the more precise the Peano-Hilbert curve can be cut into equal
|
|
|
pieces of cpu and memory load. A higher value, however, increases the global
|
|
|
tree which is stored on every MPI task, thus the total memory requirements.
|
|
|
|
|
|
-----
|
|
|
|
|
|
Moving mesh
|
|
|
===========
|
|
|
|
|
|
**DesNumNgb**
|
|
|
|
|
|
This sets the desired number of nearest neighbors for an initial density/size
|
|
|
estimate for gas cells during code startup.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**MaxNumNgbDeviation**
|
|
|
|
|
|
This sets the allowed variation of the number of neighbours around the target
|
|
|
value ``DesNumNgb``. A larger tolerance will reduce the number of iterations.
|
|
|
to find the correct radius.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**MaxVolumeDiff**
|
|
|
|
|
|
``REFINEMENT_VOLUME_LIMIT``
|
|
|
|
|
|
Maximum difference in volume of two neighboring cells. This avoids large
|
|
|
cell-size gradients in the mesh which might cause numerical inaccuracies.
|
|
|
In case where the volume of a cell exceeds ``MaxVolumeDiff`` times the volume
|
|
|
of the smallest neighboring cell, the cell is refined, irrespective of other
|
|
|
refinement criteria.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**MinVolume**
|
|
|
|
|
|
``REFINEMENT_VOLUME_LIMIT``
|
|
|
|
|
|
Global minimal volume a cell is allowed to have, irrespective of other
|
|
|
refinement and derefinement criteria.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**MaxVolume**
|
|
|
|
|
|
``REFINEMENT_VOLUME_LIMIT``
|
|
|
|
|
|
Global maximal volume a cell is allowed to have, irrespective of other
|
|
|
refinement and derefinement criteria.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**MeanVolume**
|
|
|
|
|
|
``NODEREFINE_BACKGROUND_GRID``
|
|
|
|
|
|
Mean volume of cells. In case ``NODEREFINE_BACKGROUND_GRID``, cells with
|
|
|
more than 10% or this volume will not be derefined. Used for cosmological
|
|
|
zoom simulations.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**CellMaxAngleFactor**
|
|
|
|
|
|
not ``VORONOI_STATIC_MESH``,
|
|
|
``REGULARIZE_MESH_FACE_ANGLE``
|
|
|
|
|
|
Cell "roundness" criterion.
|
|
|
The face angle of an interface of a cell is defined as the square root of the
|
|
|
area divided by pi, divided by the distance to the face. The maximum face
|
|
|
angle is the maximum of this values for all faces in a given cell. This value
|
|
|
is a measure for the "roundness" of a cell.
|
|
|
If this value exceeds 1.5 times ``CellMaxAngleFactor``, the cell is not
|
|
|
allowed to be refined, i.e. highly elongated cells are not allowed to be
|
|
|
refined. In addition to this, if the cell exceeds 0.75 times
|
|
|
``CellMaxAngleFactor``, the movement of the mesh-generating point will
|
|
|
deviate from the pure Lagrangian motion to make the cell rounder.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**CellShapingFactor**
|
|
|
|
|
|
not ``VORONOI_STATIC_MESH``,
|
|
|
not ``REGULARIZE_MESH_FACE_ANGLE``
|
|
|
|
|
|
Alternative "roundness" criterion. This criterion uses the distance between
|
|
|
center of mass and mesh-generating point as a measure for roundness. If this
|
|
|
distnce exceeds twice the cell radius times ``CellShapingFactor``, the cell
|
|
|
will not be refined.
|
|
|
If this distance exceeds 0.75 times the cell radius times
|
|
|
``CellShapingFactor`` the movement of the mesh-generating point will deviate
|
|
|
from pure Lagrangian motion to make the cell rounder.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**CellShapingSpeed**
|
|
|
|
|
|
not ``VORONOI_STATIC_MESH``
|
|
|
|
|
|
Determines the speed of the regularization of the mesh.
|
|
|
``CellShapingSpeed`` (times a characteristic speed) is the speed by which
|
|
|
the mesh is regularized (i.e. speed by which the motion of a mesh-generating
|
|
|
point can deviate from Lagrangian motion).
|
|
|
Higher values will lead to round cells in fewer timesteps, but will also
|
|
|
introduce more numerical noise.
|
|
|
|
|
|
-----
|
|
|
|
|
|
Refinement and derefinement
|
|
|
===========================
|
|
|
|
|
|
**ReferenceGasPartMass**
|
|
|
|
|
|
``REFINEMENT``
|
|
|
|
|
|
For comoving runs, it can either be given a non-zero value, in which case
|
|
|
this value * ``MassFactor`` is used as the target mass, or it can be given 0,
|
|
|
in which case the code calculates the mean cell mass. For non-comoving runs,
|
|
|
it must be given non-zero, otherwise the run will exit.
|
|
|
If ``REFINEMENT_HIGH_RES_GAS`` is enabled, then: if
|
|
|
ReferenceGasPartMass==0 in the parameter file, then all gas present in the
|
|
|
ICs will be allowed to be (de-)refined (and the code calculates the reference
|
|
|
mass as the mean mass of those cells for which (de-)refinement is allowed),
|
|
|
and if that is not desired, then ReferenceGasPartMass should be set to the
|
|
|
correct value, in which case only gas with initial
|
|
|
mass<1.2*ReferenceGasPartMass will be allowed to be (de-)refined.
|
|
|
In case of ``GENERATE_GAS_IN_ICS``, only the gas cells split off from
|
|
|
particle type 1 (usually the high-res dark matter particles) are flagged for
|
|
|
(de-)refinement, i.e. only these gas cells will be considered for the
|
|
|
``ReferenceGasPartMass`` calculation (only in case ``ReferenceGasPartMass=0``
|
|
|
in parameter file).
|
|
|
|
|
|
-----
|
|
|
|
|
|
**TargetGasMassFactor**
|
|
|
|
|
|
``REFINEMENT``
|
|
|
|
|
|
The target gas cell mass, where (de-)refinement is triggered if a given cell
|
|
|
deviates by more than a factor of 2.0 above or below this value.
|
|
|
Multiplicative factor with respect to the mean cell mass.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**RefinementCriterion**
|
|
|
|
|
|
``REFINEMENT``
|
|
|
|
|
|
Selects the criterion for refinement; "0" no refinement, "1" target mass
|
|
|
refinement, "2" Jeans stability refinement cirtrion.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**DerefinementCriterion**
|
|
|
|
|
|
``REFINEMENT``
|
|
|
|
|
|
Selects the criterion for derefinement; "0" no derefinement, "1" target mass
|
|
|
derefinement, "2" Jeans stability derefinement cirtrion.
|
|
|
|
|
|
-----
|
|
|
|
|
|
Hydrodynamics
|
|
|
=============
|
|
|
|
|
|
**LimitUBelowThisDensity**
|
|
|
|
|
|
Density threshold for a specific thermal energy lower limit for low density
|
|
|
gas.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**LimitUBelowCertainDensityToThisValue**
|
|
|
|
|
|
Minimum specific thermal energy for low density gas.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**MinGasTemp**
|
|
|
|
|
|
A minimum temperature floor imposed by the code. This may be set to zero,
|
|
|
but it may be desirable to prevent the gas from becoming too cold, e.g. for
|
|
|
resolution reasons or because of lower limits in the implemented cooling
|
|
|
function. (This value is converted by the code to a minimum thermal
|
|
|
energy per unit mass assuming the mean molecular weight of neutral gas).
|
|
|
|
|
|
-----
|
|
|
|
|
|
**MinEgySpec**
|
|
|
|
|
|
Minimum specific energy allowed in a gas cell. If specific energy is smaller
|
|
|
than the value specified here, AREPO will add additional thermal energy in
|
|
|
this cell such that it reaches a specific thermal energy of ``MinEgySpec``.
|
|
|
This is mainly as a protection against negative specific energies emerging
|
|
|
from numerical round-off errors in kinetically or magnetically dominated
|
|
|
cells (keep in mind that the thermal energy is recomputed from the total
|
|
|
energy in AREPO.
|
|
|
In case this parameter is nonzero, it overrides ``MinGasTemp``.
|
|
|
If this is zero, internally, ``MinEgySpec`` will be calculated via the value
|
|
|
of ``MinGasTemp``. In case both ``MinEgySpec``and ``MinGasTemp`` are nonzero,
|
|
|
``MinGasTemp`` will only set a lower limit to the cooling.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**IsoSoundSpeed**
|
|
|
|
|
|
``ISOTHERM_EQS``
|
|
|
|
|
|
Sound speed of gas in runs with isothermal hydrodynamics.
|
|
|
|
|
|
-----
|
|
|
|
|
|
|
|
|
Gravitational softening
|
|
|
=======================
|
|
|
|
|
|
**GasSoftFactor**
|
|
|
|
|
|
The gravitational softening length of a gas cell is this value times the
|
|
|
cellsize, which is calculated as the radius of the volume-equilvalent-sphere.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**SofteningComovingTypeX**
|
|
|
|
|
|
A Plummer equivalent gravitational softening length, to be referenced by
|
|
|
one or more specific particle types. For cosmological simulations in
|
|
|
comoving coordinates, this is interpreted as a comoving softening length in
|
|
|
code length units.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**SofteningMaxPhysTypeX**
|
|
|
|
|
|
When comoving integration is used, this parameter gives the maximum physical
|
|
|
gravitational softening length corresponding to ``SofteningComovingTypeX``
|
|
|
(referenced by one or more specific
|
|
|
particle types depending on the entries of ``SofteningTypeOfPartTypeN``).
|
|
|
Depening on the relative settings of the *Comoving* and *MaxPhys* softenings,
|
|
|
the code will hence switch from a softening constant in comoving units to
|
|
|
one constant in physical units. For example, if the *MaxPhys* value is
|
|
|
exactly half the *Comoving* value, then particles using this softening type
|
|
|
will have comoving softening until`z=1` and fixed physical softenings
|
|
|
after that point in time. Code length units.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**SofteningTypeOfPartTypeX**
|
|
|
|
|
|
For each particle type in the simulation which is involved gravitational
|
|
|
calculations, it must be assigned to a "softening type", a 0-based integer
|
|
|
index corresponding to one of the above
|
|
|
``SofteningComovingTypeX``/``SofteningMaxPhysTypeX`` entry pairs.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**MinimumComovingHydroSoftening**
|
|
|
|
|
|
``ADAPTIVE_HYDRO_SOFTENING``
|
|
|
|
|
|
If this treatment for gas softenings is based used, a discrete spectrum of
|
|
|
possible softening lengths for gas cells is created at
|
|
|
startup. It contains ``NSOFTTYPES_HYDRO`` entries, controlled by
|
|
|
this 'minimum' parameter and the following 'spacing' parameter (as a
|
|
|
multiplicative factor). Code length units.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**AdaptiveHydroSofteningSpacing**
|
|
|
|
|
|
``ADAPTIVE_HYDRO_SOFTENING``
|
|
|
|
|
|
The logarithmic spacing for the adaptive gas softenings table, as described
|
|
|
above. Must be larger than one.
|
|
|
|
|
|
-----
|
|
|
|
|
|
Subfind parameters
|
|
|
==================
|
|
|
|
|
|
**DesLinkNgb**
|
|
|
|
|
|
``SUBFIND``
|
|
|
|
|
|
The (integer) minimum number of particles/cells, of all types, for Subfind
|
|
|
groups. If a Subfind group is identified with fewer than this number of
|
|
|
total particles/cells, it is discarded. Note that this means many small
|
|
|
friends-of-friends groups (with a nomimal minimum number of 32 member
|
|
|
particles) may frequently have no sufficiently large Subfind groups, and
|
|
|
so will have ``GroupFirstSub==-1`` indicating that that FoF has no central
|
|
|
subhalo in addition to no satellite subhalos.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**ErrTolThetaSubfind**
|
|
|
|
|
|
``SUBFIND``
|
|
|
|
|
|
This has the same meaning as the ``ErrTolTheta`` parameter, i.e. the tree
|
|
|
opening angle used to control the accuracy of the gravity calculation, for
|
|
|
uses within the Subfind algorithm.
|
|
|
|
|
|
-----
|
|
|
|
|
|
Cooling and star formation
|
|
|
==========================
|
|
|
|
|
|
**CoolingOn**
|
|
|
|
|
|
If set to "1", gas looses energy through a (optically-thin) radiative
|
|
|
cooling model at each timestep. Can only be set to zero if ``COOLING`` is
|
|
|
not set.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**StarformationOn**
|
|
|
|
|
|
If set to "1", gas can (stochastically) convert into collisionless star
|
|
|
particles based on a star formation model.
|
|
|
Can only be set to zero if ``USE_SFR`` is not set.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**TreecoolFile**
|
|
|
|
|
|
``COOLING``
|
|
|
|
|
|
File path to cooling file. Possible files are available under ``./data/``.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**CritOverDensity**
|
|
|
|
|
|
``USE_SFR``
|
|
|
|
|
|
The critical (over-)density above which star formation may take place, where
|
|
|
the threshold density is then
|
|
|
|
|
|
rho_th = ``CritOverDensity`` 3 ``Omega_b`` H^2 / (8 pi G)
|
|
|
|
|
|
(redshift independent). Used in place of a critical physical density for
|
|
|
comoving integrations.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**TemperatureThresh**
|
|
|
|
|
|
``USE_SFR``
|
|
|
|
|
|
Star formation is prevented for cells which are hotter than the eEOS and
|
|
|
hotter than the TemperatureThresh parameter (in Kelvin). If this parameter is
|
|
|
very large (e.g. 1e20), then nothing is changed compared to the base model.
|
|
|
If this parameter is small (e.g. 0, 1e4, or 1e5) then star-formation will be
|
|
|
prevented in hot halo gas.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**CritPhysDensity**
|
|
|
|
|
|
``USE_SFR``
|
|
|
|
|
|
The critical physical density above which star formation may take place
|
|
|
(in `cm^-3`). Used instead of ``CritOverDensity`` for non-comoving runs.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**FactorSN**
|
|
|
|
|
|
``USE_SFR``
|
|
|
|
|
|
The variable giving the mass fraction of massive stars
|
|
|
(``> 8 Msun``) formed for each initial population of stars. This is
|
|
|
thus determined by the stellar IMF.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**FactorEVP**
|
|
|
|
|
|
``USE_SFR``
|
|
|
|
|
|
The variable ``A``, giving the efficiency of the cloud evaporation
|
|
|
process.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**TempSupernova**
|
|
|
|
|
|
``USE_SFR``
|
|
|
|
|
|
The "supernova temperature" ``T_SN`` of the hot intercloud medium in Kelvin.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**TempClouds**
|
|
|
|
|
|
``USE_SFR``
|
|
|
|
|
|
The "cold cloud temperature" ``T_c``, in Kelvin.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**MaxSfrTimescale**
|
|
|
|
|
|
``USE_SFR``
|
|
|
|
|
|
This is the star-formation timescale ``t_0`` at the threshold density, such that
|
|
|
the local star-formation timescale is then calculated as
|
|
|
|
|
|
t_star(rho) = t_0 (rho / rho_th)^-0.5
|
|
|
|
|
|
-----
|
|
|
|
|
|
Sphericaly symmetric simulations
|
|
|
================================
|
|
|
|
|
|
**CoreRadius**
|
|
|
|
|
|
``ONEDIMS_SPHERICAL``
|
|
|
|
|
|
Inner radius (position of boundary conditions) of 1d spherical simulation.
|
|
|
|
|
|
-----
|
|
|
|
|
|
**CoreMass**
|
|
|
|
|
|
``ONEDIMS_SPHERICAL``
|
|
|
|
|
|
Mass enclosed within the inner boundary radius in 1d spherical simulations.
|
|
|
Required for gravity calculation. |