Parameters in the define.h File

This file contains all default values of the parameters in the param.dat file. It also contains constants and additional parameters for GENGA. When a value is changed in this file, then GENGA needs to be recompiled.

Use old Shuffle

CUDA has replaced the shuffle functions __shfl_xor to a new function __shfl_xor_sync. GENGA offers a flag to switch between the two versions. If an old CUDA version is used (< CUDA 9.0) then the def_OldShuffle parameter in the define.h file must be set to 1.

0: use new sync shuffle version (default)
1: use old shuffle version

Ignore Lock File

def_IgnoreLockFile, flag to set the behaviour of starting (not restarting) a new simulation - 0: When previous output files exist, then GENGA can only be started again after deleting the lock.dat file. This option prevents that existing data is overwritten. - 1: GENGA can be started even if previous files exist. Previous files are deleted and overwritten.

Memory options

def_MaxColl (integer): Maximum number of collisions per time step that can be stored.

When a collision happens, then the details of the collisions are stored in an internal buffer on the GPU. After the time, this buffer is transferred to the CPU and the information written into the collision file. The size of this buffer is specified by def_MaxColl. When more collisions occur in the same time step, then the integration is stopped and an error message written.

Increasing this number also increases the total amount of needed memory.

(default = 120)
def_SLevelsMax (integer): Define the maximum number of symplectic substep levels.

Increasing this number will increase the amount of needed memory.

See Higher level changeover functions
def_NSetElementsMax (integer): Define the maximum number of lines in the Set-Elements file.

See Set-elements function.

Other

def_tol: Tolerance in Bulirsch Stoer integrator (default = 1.0e-12).
def_dtmin: Minimal time step in Bulirsch Stoer integrator (default = 1.0e-17).
def_NFileNameDigits: set number of digits in the names of the output files (default = 12).
def_pc: Factor in Pre-checker, pairs with \(r_{ij}^2 < \text{pc} \, r_\text{crit}^2\) are considered as close encounter candidates.

(default = 3.0)

See Finding close encounter candidates.
def_pcf: Single precision version of def_pc, used when Do Kick in single precision = 1.

(default = 3.0f)

See Finding close encounter candidates and Use single precision in kick forces.
def_cef: Factor in close encounter detector, pairs with \(r_{ij}^2 < \text{cef} \, r_\text{crit}^2\) are considered as close encounter pairs.

(default = 1.0)

See Finding close encounter candidates.
def_GMax: Defines the maximum size of close encounter groups as \(2^\text{GMax}\).

(default = 20)
def_poincareFlag: Flag to enable the Poincare surface of section calculation

See Poincare surface of section
- 0: Poincare surface of section is not calculated
- 1: Poincare surface of section is calculated
def_Rand_Min: lower limit for acceptable random number range (default = 1.0e-12).

See Model for small bodies collisions.

Physical constants

The following physical constants are used by GENGA and can be changed in this section of the define.h file:

def_ksq = 1.0

Squared Gaussian gravitational constant in current units
def_Kg 2.959122082855911e-4

Squared Gaussian gravitational constant in \(AU^3 day^{-2} M_\odot^{-1}\) , used for conversion
dayUnit 0.01720209895
def_AU 149597870700.0

AU in m
def_Solarmass 1.98855e30

Solar Mass in kg
def_c 299792458.0

speed of light in m/s
def_cm 10065.3201686

speed of light in AU / day * 0.0172020989
def_sigma 5.670373e-8

Stefan Boltzmann constant in \(J m^{-2} s{^-1} K{^-4}\)

Parameters for the gas disk

See Gas disk

def_Gasnz_g: Number of cells in z direction for gas grid
def_Gasnz_p: Number of cells in z direction for particle grid
def_h_1: scale height at 1AU for c = 1km/s
def_M_Enhance: factor for enhancement
def_Mass_pl: factor for enhancement
def_fMass_min: factor for enhancement
def_Gas_cd: numerical gas drag coefficient