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# Parameterfile
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# _Parameterfile:
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Parameterfile
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*****************
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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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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 simulation
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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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there are either missing parameters for the given configuration Arepo was
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compiled with, or if there are obsolete parameters. 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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... | ... | @@ -32,7 +35,7 @@ Initial conditions |
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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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preceded 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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... | ... | @@ -61,7 +64,7 @@ Initial conditions |
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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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The direction is encoded by sum(2^k), where k is the index of direction
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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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... | ... | @@ -81,7 +84,7 @@ Initial conditions |
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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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Factor by which the ICs are duplicated in each dimension. Should be an
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integer.
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-----
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... | ... | @@ -124,7 +127,7 @@ Output file names and formats |
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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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recognized 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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... | ... | @@ -159,7 +162,7 @@ Output file names and formats |
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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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then 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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... | ... | @@ -179,7 +182,7 @@ Output frequency |
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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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The value specified 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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... | ... | @@ -267,7 +270,7 @@ Memory allocation |
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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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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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... | ... | @@ -280,7 +283,7 @@ Simulated time and spatial extent |
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**BoxSize**
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The boxsize for the simulation, in internal code units.
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The box size 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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... | ... | @@ -340,7 +343,7 @@ Cosmological parameters |
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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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density 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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... | ... | @@ -360,8 +363,8 @@ Cosmological parameters |
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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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proper (i.e. non-comoving) cgs units are required (e.g. for radiative
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cooling physics). In other cases, use 1.0.
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-----
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... | ... | @@ -370,8 +373,8 @@ System of units |
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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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This sets the internal velocity unit in **cm/s**. For example, the
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choice of ``1e5`` sets the velocity unit to 1.0 *km/s*.
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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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... | ... | @@ -387,7 +390,7 @@ System of units |
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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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This sets the internal mass unit in **g/h**, where H_0 = 100 h km/s/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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... | ... | @@ -414,7 +417,7 @@ Gravitational force accuracy |
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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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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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... | ... | @@ -429,7 +432,8 @@ Gravitational force accuracy |
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**ErrTolForceAcc**
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The accuracy parameter for the relative opening criterion for the tree walk. Only used if ``ErrTolTheta 0``.
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The accuracy parameter for the relative opening criterion for the tree walk.
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Only used if ``ErrTolTheta 0``.
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-----
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... | ... | @@ -439,8 +443,8 @@ 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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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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... | ... | @@ -497,7 +501,7 @@ Domain decomposition |
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Number of domains per MPI task. Consequently, the domain decomposition will
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cut computational box in ``MultipleDomains`` times number of tasks chunks.
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Too few of them will lead to cpu load and memory inbalances, too many to more
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Too few of them will lead to cpu load and memory imbalances, too many to more
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MPI communication as there are more domain boundaries.
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-----
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... | ... | @@ -524,7 +528,7 @@ Moving mesh |
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**MaxNumNgbDeviation**
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This sets the allowed variation of the number of neighbours around the target
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This sets the allowed variation of the number of neighbors around the target
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value ``DesNumNgb``. A larger tolerance will reduce the number of iterations.
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to find the correct radius.
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... | ... | @@ -595,7 +599,7 @@ not ``REGULARIZE_MESH_FACE_ANGLE`` |
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Alternative "roundness" criterion. This criterion uses the distance between
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center of mass and mesh-generating point as a measure for roundness. If this
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distnce exceeds twice the cell radius times ``CellShapingFactor``, the cell
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distance exceeds twice the cell radius times ``CellShapingFactor``, the cell
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will not be refined.
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If this distance exceeds 0.75 times the cell radius times
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``CellShapingFactor`` the movement of the mesh-generating point will deviate
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... | ... | @@ -657,7 +661,7 @@ Refinement and derefinement |
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``REFINEMENT``
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Selects the criterion for refinement; "0" no refinement, "1" target mass
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refinement, "2" Jeans stability refinement cirtrion.
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refinement, "2" Jeans stability refinement criterion.
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-----
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... | ... | @@ -666,7 +670,7 @@ Refinement and derefinement |
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``REFINEMENT``
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Selects the criterion for derefinement; "0" no derefinement, "1" target mass
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derefinement, "2" Jeans stability derefinement cirtrion.
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derefinement, "2" Jeans stability derefinement criterion.
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-----
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... | ... | @@ -699,15 +703,15 @@ Hydrodynamics |
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**MinEgySpec**
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Minimum specific energy allowed in a gas cell. If specific energy is smaller
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than the value specified here, AREPO will add additional thermal energy in
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than the value specified here, Arepo will add additional thermal energy in
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this cell such that it reaches a specific thermal energy of ``MinEgySpec``.
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This is mainly as a protection against negative specific energies emerging
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from numerical round-off errors in kinetically or magnetically dominated
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cells (keep in mind that the thermal energy is recomputed from the total
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energy in AREPO.
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energy in Arepo.
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In case this parameter is nonzero, it overrides ``MinGasTemp``.
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If this is zero, internally, ``MinEgySpec`` will be calculated via the value
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of ``MinGasTemp``. In case both ``MinEgySpec``and ``MinGasTemp`` are nonzero,
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of ``MinGasTemp``. In case both ``MinEgySpec`` and ``MinGasTemp`` are nonzero,
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``MinGasTemp`` will only set a lower limit to the cooling.
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-----
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... | ... | @@ -727,7 +731,7 @@ Gravitational softening |
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**GasSoftFactor**
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The gravitational softening length of a gas cell is this value times the
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cellsize, which is calculated as the radius of the volume-equilvalent-sphere.
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cell size, which is calculated as the radius of the volume-equilvalent sphere.
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-----
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... | ... | @@ -746,11 +750,11 @@ Gravitational softening |
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gravitational softening length corresponding to ``SofteningComovingTypeX``
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(referenced by one or more specific
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particle types depending on the entries of ``SofteningTypeOfPartTypeN``).
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Depening on the relative settings of the *Comoving* and *MaxPhys* softenings,
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Depending on the relative settings of the *Comoving* and *MaxPhys* softenings,
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the code will hence switch from a softening constant in comoving units to
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one constant in physical units. For example, if the *MaxPhys* value is
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exactly half the *Comoving* value, then particles using this softening type
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will have comoving softening until`z=1` and fixed physical softenings
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will have comoving softening until `z=1` and fixed physical softenings
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after that point in time. Code length units.
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-----
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... | ... | @@ -758,7 +762,7 @@ Gravitational softening |
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**SofteningTypeOfPartTypeX**
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For each particle type in the simulation which is involved gravitational
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calculations, it must be assigned to a "softening type", a 0-based integer
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calculations, it must be assigned to a "softening type", an integer
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index corresponding to one of the above
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``SofteningComovingTypeX``/``SofteningMaxPhysTypeX`` entry pairs.
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... | ... | @@ -768,7 +772,7 @@ Gravitational softening |
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``ADAPTIVE_HYDRO_SOFTENING``
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If this treatment for gas softenings is based used, a discrete spectrum of
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If this treatment for gas softenings is used, a discrete spectrum of
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possible softening lengths for gas cells is created at
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startup. It contains ``NSOFTTYPES_HYDRO`` entries, controlled by
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this 'minimum' parameter and the following 'spacing' parameter (as a
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... | ... | @@ -781,7 +785,8 @@ Gravitational softening |
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``ADAPTIVE_HYDRO_SOFTENING``
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The logarithmic spacing for the adaptive gas softenings table, as described
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above. Must be larger than one.
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above. This is the multiplicative factor by which the next discrete softening
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length is larger than the previous one. Consequently, must be larger than unity.
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-----
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... | ... | @@ -795,7 +800,7 @@ Subfind parameters |
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The (integer) minimum number of particles/cells, of all types, for Subfind
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groups. If a Subfind group is identified with fewer than this number of
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total particles/cells, it is discarded. Note that this means many small
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friends-of-friends groups (with a nomimal minimum number of 32 member
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friends-of-friends groups (with a nominal minimum number of 32 member
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particles) may frequently have no sufficiently large Subfind groups, and
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so will have ``GroupFirstSub==-1`` indicating that that FoF has no central
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subhalo in addition to no satellite subhalos.
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... | ... | @@ -897,7 +902,7 @@ Cooling and star formation |
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``USE_SFR``
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The "supernova temperature" ``T_SN`` of the hot intercloud medium in Kelvin.
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The "supernova temperature" ``T_SN`` of the hot inter-cloud medium in Kelvin.
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-----
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... | ... | |