Runtime Parameters: Timestep

This page describes various timestep constraints. See also Section 2.6 in the GAMER-2 code paper.

Compilation Options

Related options: none

Runtime Parameters

Parameters described on this page: DT__FLUID,   DT__FLUID_INIT,   DT__GRAVITY,   DT__PHASE,   DT__PARVEL,   DT__PARVEL_MAX,   DT__PARACC,   DT__MAX_DELTA_A,   DT__SYNC_PARENT_LV,   DT__SYNC_CHILDREN_LV,   OPT__DT_USER,   OPT__DT_LEVEL,   OPT__RECORD_DT,   AUTO_REDUCE_DT,   AUTO_REDUCE_DT_FACTOR,   AUTO_REDUCE_DT_FACTOR_MIN  

Other related parameters: [[]]  

Parameters below are shown in the format:   Name   (Valid Values)   [Default Value]

• DT__FLUID   (≥0.0; <0.0 → set to default)   [-1.0]

  • Description: Courant–Friedrichs–Lewy (CFL) safety factor for the hydrodynamic solver. The default value and stable regime depend on the adopted fluid scheme. See Section 2.6, Eqs. [1-2] in the GAMER-2 code paper for the exact formulae.
  • Restriction:

• DT__FLUID_INIT   (≥0.0; <0.0 → set to default)   [DT__FLUID]

  • Description: CFL safety factor for the hydrodynamic solver at the first step. This could be useful for the cases where the first step requires a much smaller timestep.
  • Restriction: Useless for restart.

• DT__GRAVITY   (≥0.0; <0.0 → set to default)   [-1.0]

  • Description: Safety factor when determining timestep from the gravitational acceleration of fluid. See Section 2.6, Eq. [3] in the GAMER-2 code paper for the exact formula.
  • Restriction:

• DT__PARVEL   (≥0.0)   [0.5]

  • Description: Safety factor when determining timestep from the particle velocity. See Section 2.6, Eq. [4] in the GAMER-2 code paper for the exact formula.
  • Restriction:

• DT__PARVEL_MAX   (≥0.0; <0.0 → off)   [-1.0]

  • Description: Maximum allowed value of the timestep determined from the particle velocity. This can be useful when, for example, all particles are initially at rest, for which the timestep can be infinity.
  • Restriction:

• DT__PARACC   (>0.0; ≤0.0 → off)   [0.5]

  • Description: Safety factor when determining timestep from the particle acceleration. See Section 2.6, Eq. [3] in the GAMER-2 code paper for the exact formula.
  • Restriction: Only applicable when adopting the compilation option STORE_PAR_ACC.

• DT__MAX_DELTA_A   (≥0.0)   [0.01]

  • Description: Maximum allowed fraction of increase in the cosmic scale factor a. Specifically, it enforces Δa ≤ DT__MAX_DELTA_A ⋅ a.
  • Restriction: Only applicable when adopting the compilation option COMOVING.

• DT__SYNC_PARENT_LV   ()   []

  • Description:
  • Restriction:

• DT__SYNC_CHILDREN_LV   ()   []

  • Description:
  • Restriction:

• OPT__DT_USER   ()   []

  • Description:
  • Restriction:

• OPT__DT_LEVEL   ()   []

  • Description:
  • Restriction:

• OPT__RECORD_DT   ()   []

  • Description:
  • Restriction:

• AUTO_REDUCE_DT   ()   []

  • Description:
  • Restriction:

• AUTO_REDUCE_DT_FACTOR   ()   []

  • Description:
  • Restriction:

• AUTO_REDUCE_DT_FACTOR_MIN   ()   []

  • Description:
  • Restriction:

Links

• Main page of Runtime Parameters