Parameters in the param.dat file

All parameters in the param.dat file can be changed with recompiling GENGA. Most parameters are optional, if they are not included in the param.dat file, then their default values are used. The default values are set in the define.h file.

Main parameters

  • Time step in days, (default = 6.0 days)
    Should be minimal ca. 30 steps per orbit for the second order integrator.
    Can be set to negative values for an integration backward in time.
  • Output name (default = “test”).
    All output files will contain this name,
  • Energy output interval, Interval when energy information is written, in units of timesteps, (default = 100).
    See The Energy Output File: Energy<name>.dat

    • when set to 0, then no energy output is written.

    • when set to -1, then only the very last energy output is written (or when a simulation is stopped).

  • Coordinates output interval, Interval when output coordinates are written to a file, in units of timesteps, (default = 100).
    See The Coordinate Output Files: Out<name>.dat

    • when set to 0, then no coordinate output is written.

    • when set to -1, then only the very last coordinate output is written (or when a simulation is stopped).

  • Number of outputs per interval, Can be used to write outputs at a number of consecutive time steps at each output Interval.
    In units of time steps.
    See Number of outputs per interval.
    (default = 1).
  • Coordinate output buffer, can be used to temporarily store outputs in a GPU buffer before transferring the data back
    to the CPU. When outputs are written frequently, then this option can speed up the data transfer.
    In units of time steps.
    (default = 1)
    The energy outputs within a buffer size are skipped in this mode.
  • Irregular output calendar, filename of the irregular output calendar file,
    Can be use to write coordinate and energy outputs at specified times.
    See Irregular output times

    • - : nothing happens

    • <calendar file name>: the calendar file is used and irregular output files are written.

  • Integration steps, total number of time steps to run.
    (default = 1000 time steps)
  • Input file, (default = ‘inital.dat’)
    Filename (or path) of the initial conditions file
    The file must exist.
    See The initial conditions
  • Input file Format: Format of the initial conditions file.
    (default = << x y z m vx vy vz >>)
    See The initial conditions format
  • Output file Format: Format of the coordinate output files.
    (default = << t i m r x y z vx vy vz Sx Sy Sz amin amax emin emax aec aecT encc test >>)
    See Output File Format
  • Angle units, unit of angles in the initial conditions file, (default = radians)
    either ‘radians’ or ‘degrees’.
    affects inc, O, w and M.
  • Use output binary files, text or binary file format for coordinate output files.
    - 0 (default): Use text files for coordinate output files.
    - 1: Use binary files for coordinate output files.
    See The Coordinate Output Files: Out<name>.dat
  • Default rho, value for the densities when no value (no rho and no r) is given in Input file Format:
    in g/cm^3 (default = 2.0)
    See The initial conditions format
  • Restart timestep, can be used to continue a finished simulation or the restart at a given time step
    - 0: Start a new simulation, old files are overwritten (default).
    - > 0: Restart GENGA at this time step.
    - -1: Continue at the last written output time step.
    See Restarting GENGA to continue simulations

Stellar parameters

  • Central Mass
    Mass of the central star, in Solar Masses (default = 1.0)
  • Star Radius
    Physical radius of the central star in AU (default = 0.00465475877 AU = Solar radius)
  • Star Love Number
    Love number of the central star (default = 1.0)
  • Star fluid Love Number
    Fluid Love number of the central star (default = 1.0)
  • Star tau
    Time lag for tidal force of the central star (default = 0.0)
  • Star spin_x
    X- component of the spin of the central star, in \(M_{\odot} AU^2 / day \cdot 0.01720209895\) (default = 0.0)
    See Spin
  • Star spin_y
    Y- component of the spin of the central star, in \(M_{\odot} AU^2 / day \cdot 0.01720209895\) (default = 0.0)
    See Spin
  • Star spin_z
    Z- component of the spin of the central star, in \(M_{\odot} AU^2 / day \cdot 0.01720209895\) (default = 0.0)
    See Spin
  • Star Ic
    Moment of inertia of the central star, dimensionless (I/(MR^2) (default = 0.4)
    This is used to convert between spin and rotational period.
    See Spin
  • J2
    J2 value for additional gravitational multipole expansion (default = 0.0)
    See J2: additional gravitation multipole expansion
  • J2 radius
    Mean radius of mass distribution for additional gravitational multipole expansion, in AU (default = 0.0)
    See J2: additional gravitation multipole expansion

Integrator options

  • n1: Parameter to set critical radius for close encounters (default = 3.0).
    See The n1 and n2 values
  • n2: Parameter to set critical radius for close encounters (default = 0.4).
    See The n1 and n2 values
  • Use Test Particles, flag to enable test particle mode (default = 0)
    See Using test particles, and Particle Minimum Mass.

    • 0: full gravity mode, compute force between all pairs of particles.

    • 1: test particle mode, small bodies do not affect other bodies.

    • 2: semi active mode, small bodies do only affect large bodies but not other small bodies.

  • Particle Minimum Mass, threshold mass between small and large particles (default = 0.0)
    All particles with a smaller mass than this value are treated as test particles (if Use Test Particles > 0).
    When Use Test Particles = 0, then this parameter has no affect.
  • Symplectic recursion levels, number of symplectic levels in the hybrid symplectic integration method (default = self tuned).

    • -1: Use self tuning routine at integration start, to find the fastest option between levels, 1, 2 or 3.

    • > 0: Use this number of symplectic recursion levels.

    See Higher level changeover functions.
  • Symplectic recursion sub steps, number of sub steps per symplectic level in the hybrid symplectic integration method (default = self tuned).

    • -1: Use self tuning routine at integration start, to find the fastest option between sub steps, 2, 4, 8 or 10.

    • > 1: Use this number of sub steps per symplectic level.

    See Higher level changeover functions.
  • Minimum number of bodies, (default = 0)
    When the number of bodies (not including test particles) gets smaller than this number, then the simulation will be stopped.
  • Minimum number of test particles (default = 0)
    when the number of test particles gets smaller than this number, then the simulation will be stopped.
  • Inner truncation radius, in AU (default = 0.2)
    When the distance of a particle to the central mass is smaller than this number, then the particle is removed from the simulation.
    See Ejections
  • Outer truncation radius in AU (default = 50.0)
    When the distance of a particle to the central mass is larger than this number, then the particle is removed from the simulation.
    See Ejections
  • Order of integrator, set the order of the symplectic integrator.
    See The order of the symplectic integrator

    • 2: second order (default)

    • 4: fourth order

    • 6: sixth order

Memory options

Options for the a-e and a-i grid

See The a-e and a-i grid.

  • Use aeGrid, flag to enable the a-e and a-i grids, (default = 0)

    • 0: nothing happens

    • 1; a-e and a-i grids are created

  • aeGrid amin, minimal value of the same-major axis dimension, in AU.
    (default = 0.0)
  • aeGrid amax, maximal value of the same-major axis dimension, in AU.
    (default = 5.0)
  • aeGrid emin, minimal value of the eccentricity dimension.
    (default = 0.0)
  • aeGrid emax, maximal value of the eccentricity dimension.
    (default = 1.0)
  • aeGrid imin, minimal value of the inclination dimension, in radians.
    (default = 0.0)
  • aeGrid imax, maximal value of the inclination dimension, in radians.
    (default = 0.1)
  • aeGrid Na, number of points in the same-major axis dimension.
    (default = 10)
  • aeGrid Ne, number of points in the eccentricity dimension.
    (default = 10)
  • aeGrid Ni, number of points in the inclination dimension.
    (default = 10)
  • aeGrid Start Count, starting time step when a-e and a-i grid start, in units of time steps
    (grids will start at the next bigger coordinate output step)
    (default = 0)
  • aeGrid name, name of the grid files.
    (default = A)

Options for the gas disk

See Gas disk

  • Use gas disk: Flag to enable the gas disk. Individual effects can be selected with the following parameters.

    • 0 (default): Do not use a gas disk.

    • 1: Use a gas disk with the following parameters.

  • Use gas disk potential: Flag to enable the gas disk potential effect.

    • 0: Do not use the gas disk potential effect

    • 1 (default): apply the gas disk potential to all particles

    • 2: apply the gas disk potential only to particles with m < Gas Mgiant

  • Use gas disk enhancement: Flag to enable the gas disk enhancement effect.

    • 0 (default): Do not use the gas disk enhancement.

    • 1: apply the gas disk enhancement to all particles.

    • 2: apply the gas disk enhancement only to particles with m < Gas Mgiant

  • Use gas disk drag: Flag to enable the gas drag.

    • 0: Do not apply the gas drag.

    • 1: apply the gas drag to all particles.

    • 2 (default): apply the gas drag only to particles with m < Gas Mgiant

  • Use gas disk tidal dampening: Flag to enable gas disk tidal dampening (Type I migration).

    • 0: Do not use tidal dampening.

    • 1: apply tidal dampening to all particles.

    • 2 (default): apply tidal dampening only to particles with m < Gas Mgiant.

  • Gas disk inner edge: The inner edge of the gas disk in AU.
    (default = 0.1 AU)
  • Gas disk outer edge: The outer edge of the gas disk in AU.
    (default = 35.0 AU)
  • Gas disk grid outer edge: The outer edge of the gas disk grid in AU.
    (default = 15.0 AU)
  • Gas disk grid dr: The r-spacing of the gas disk grid in AU.
    (default = 0.1 AU)
  • Gas dTau_diss: The dissipation time for the gas disk in years.
    (default = 10000 yr)
  • Gas Sigma_10: The gas surface density at 1 AU, in g/\(\text{cm}^3\).
    (default = 2000 g/\(\text{cm}^3\))
  • Gas alpha: The power law exponent for the gas disk surface density.
    (default = 1).
  • Gas beta: The power law exponent for the gas disk scale height.
    (default = 0.25).
  • Gas Mgiant: Mass limit for gas effects, in Solar masses. If m > Mgiant, the gas drag, gas potential and tidal dampening is not applied to that particle.
    (default = 1.0E-4).
  • Gas file name: Optional filename for using individual gas disk structures.

    • ‘-’ (No file name specified, default). Use the gas disk with the above specified parameters.

    • else: The specified file is read to set the gas disk parameters (time, r, Sigma and h).

Non-Newtonian forces

  • Solar Constant : Solar constant at 1 AU in W / \(\text{m}^2\) (default 1367.0)

  • Use GR: Flag to enable General Relativity corrections
    See General Relativity Corrections

    • 0 (default): no GR correction

    • 1: use GR Hamiltonian splitting

    • 2: use implicit midpoint with GR force

    • 3: use GR force directly (not symplectic)

  • Use Tides: Flag to enable tidal forces
    See Tidal Forces

    • 0 (default): no tidal forces

    • 1: use tidal forces

  • Use Rotational Deformation: Flag to enable rotational deformation forces
    See Rotational Deformation

    • 0 (default): no rotational deformation force

    • 1: use rotational deformation force

  • Use force : Old parameter to enable GR, tidal or rotational deformation.
    This parameter is outdated, use Use GR, Use Tides or Use Rotational Deformation instead.

    • 0 (default) no force applied

    • 1: Use GR correction with Hamiltonian splitting

    • 2: Use tidal forces

    • 4: Use rotational deformation

    • 3: GR + tidal force

    • 5: GR + rotational deformation

    • 6: Tidal force + rotation deformation

    • 7: GR + tidal force + rotation deformation

  • Use Yarkovsky: Flag for Yarkovsky effect
    See Yarkovsky effect

    • 0 (default): no Yarkovsky effect

    • 1: use Yarkovsky effect \(\mathbf{a_Y}\)

    • 2: use time averaged Yarkovsky effect \(\frac{da}{dt}\)

  • Yarkovsky Interval, in time steps: Interval in which the Yarkovsky model is called (default 1).
    See Yarkovsky effect
  • Use Poynting-Robertson: Flag for Poynting-Robertson effect
    See Poynting-Robertson effect

    • 0 (default) : no Poynting-Robertson effect

    • 1: use Poynting-Robertson effect \(\mathbf{a_{PR}}\)

    • 2: use time averaged Poynting-Robertson effect \(\frac{da}{dt}\) and \(\frac{de}{dt}\)

  • Poynting-Robertson Interval, in time steps: Interval in which the Poynting-Robertson model is called (default 1).
    See Poynting-Robertson effect
  • Radiation Pressure Coefficient Qpr, used in the Poynting-Robertson effect, in general assumed to be 1.
    See Poynting-Robertson effect
    default = 1.0
  • Solar Wind factor, used in the Poynting-Robertson effect scheme 1.
    Ratio of solar wind drag to Poynting-Robertson drag.
    See Solar Wind
    default = 0.0
  • Asteroid emissivity eps
    Thermal emissivity factor \(\epsilon\), used in the Yarkovsky effect.
    See Yarkovsky effect
    default = 0.95
  • Asteroid density rho, in kg/ \(\text{m}^3\)
    Used in Yarkovsky effect, Poynting-Robertson effect and small bodies collision model
    See Yarkovsky effect, Poynting-Robertson effect, Model for small bodies collisions
    default = 3500.0 kg/ \(\text{m}^3\)
  • Asteroid specific heat capacity C, in \(\text{J} \, \text{kg}^{-1} \text{K}^{-1}\)
    Used in Yarkovsky effect
    See Yarkovsky effect
    default = 680 \(\text{J} \, \text{kg}^{-1} \text{K}^{-1}\)
  • Asteroid albedo A, Bond albedo, used for Yarkovsky effect.
    See Yarkovsky effect
    default = 0.2
  • Asteroid thermal conductivity K, in \(\text{W} \, \text{m}^{-1} \text{K}^{-1}\)
    Used for Yarkovsky effect
    See Yarkovsky effect
    default = 2.65 \(\text{W} \, \text{m}^{-1} \text{K}^{-1}\)

Statistical small body collisions

  • Use Small Collisions: Flag to enable model for small bodies collision model
    See Model for small bodies collisions

    • 0 (default): model is not enabled

    • 1: enable rotation reset model and fragmentation model for test particles.

    • 2: enable only rotation reset model for test particles.

    • 3: enable only fragmentation model for test particles.

  • Small Collisions Interval, in time steps: Interval in which the small body collision model is called (default 1000).
    See Model for small bodies collisions
  • Nfragments: Number of additional memory size for debris particles, in particle numbers, (default 0).
    See Model for small bodies collisions or Particles Creation Model

Create particles during integration

Options for encounters

  • Report Encounters, flag to enable encounter information (default = 0).
    See Report Encounters.

    • 0: nothing happens.

    • 1: Encounter events between two bodies, with a separation less than Report Encounters Radius times the sum of their radii, are reported in the encounters-file. Encounters between test particles and other test particles are not reported.
    • 2: Report also encounters events between test particles and other test particles. This mode is only allowed when the test particle mode is used. Since the distance between test particles and other test particles is not calculated in the gravity calculation step, this mode needs another function call in order to find the encounters. See Finding close encounter candidates between test particles.
  • Report Encounters Radius, used for Report Encounters, (default = 1.0).
    In units of physical radii.
    See Report Encounters.
  • Report Encounters Cloud Size, used filter Report Encounters depending on the particle indices.
    See Report Encounters.
    • 1 (default): Encounter events between all particles are reported.
    • >1: Encounter events between particles belonging to the same particle cloud are not reported.
  • Stop at Encounter, flag to stop simulations when a close encounter between two bodies happens, (default = 0).
    See Stop at Encounter.

    • 0: nothing happens.

    • 1: Simulations are stopped when the separation between two bodies is less than Stop at Encounter Radius times the Hill radius.
  • Stop at Encounter Radius, used for Stop at Encounter, (default = 1.0).
    In units of Hill radii.

Options for collisions

  • Collision Precision, in units of a physical radius fraction. (default \(1.0^{-4}\))
    This parameter sets the tolerance of the detected collision time. See Collision precision.
    \(|\)Collision Precision\(|\) can not be smaller than \(1.0^{-10}\).

    • \(precision\) > 0: particles overlap slightly, \(r_{ij} < Ri + Rj\), \(r_{ij} > (Ri + Rj) \cdot (1 - precision)\)

    • \(precision\) < 0: particles do not overlap, \(r_{ij} > Ri + Rj\), \(r_{ij} < (Ri + Rj) \cdot (1 + precision)\)

  • Collision Time Shift, in units of a physical radius factor (default 1.0).
    Allows to backtrace collision at a point before the collision, when the bodies are separated by
    an increased physical radius.
    See Backtrace Collisions (TShift)
  • Stop at Collision, flag to stop simulations at the first collision time (default 0).
    This option is not supported in the multi simulation mode.
    See Stop at Collision

    • 0: nothing happens.

    • 1: stop simulation at the first collision time.

  • Stop Minimum Mass, used in Stop at Collision, (default \(0.0\))
    Simulations are only stopped when both bodies have a mass larger than this value.
  • Collision Model, can be used to implement a different collision model
    The default (0) is used for a perfect merger collision.
    See Collisions

Other

  • Set Elements file name: file name for the set-element table.
    See Set-elements function.

    • -: no file, set-elements function is not used (default)

    • < data table file name>: This file is used to read the set-elements data table.

  • FormatS: Output file format for multi simulation run.

    • 0: all simulations write to different files in their sub simulation directories (default).

    • 1: all simulations write to the same file in the master directory.

  • FormatT: Output file format for time steps.

    • 0: all time steps are written to different files (default).

    • 1: all time steps are written to the same file.

  • FormatP: Output file format for particles.

    • 0: all particles are written to different files.

    • 1: all particles are written to the same file (default).

  • FormatO: Output file format for file names.

    • 0: file names contain time steps (default).

    • 1: file names contain output steps.

  • Serial Grouping: Flag for exact reproducible results.
    See Exact reproducible results

    • 0: nothing happens.

    • 1: enable sorting step for exact reproducible results.

  • Do kernel tuning: Flag to enable the self tuning routing of GPU kernel parameters.
    (default = 1)
    See Use self tuning kernel parameters
  • Do Kick in single precision: Flag for precision in the kick force calculation
    See: Use single precision in kick forces

    • 0: use double precision in force terms (default)

    • 1: use single precision in force terms

Options for TTVs

  • TTV file name = -

  • RV file name = -

  • TTV steps = 1

  • Print Transits = 0

  • Print RV = 0

  • Print MCMC = 0

  • MCMC NE = 0

  • MCMC Restart = 0