fdtdx.SimulationConfig

Bases: TreeClass

Configuration settings for FDTD simulations.

This class contains all the parameters needed to configure and run an FDTD simulation, including spatial and temporal discretization, hardware backend, and gradient computation settings.

Attributes:
  • time (float) –

    Total simulation time in seconds.

  • resolution (float) –

    Spatial resolution of the simulation grid in meters.

  • backend (BackendOption) –

    Computation backend ('gpu', 'tpu', 'cpu' or 'METAL'). Defaults to "gpu".

  • dtype (dtype) –

    Data type for numerical computations. Defaults to jnp.float32.

  • courant_factor (float) –

    Safety factor for the Courant condition (default: 0.99).

  • gradient_config (GradientConfig | None) –

    Optional configuration for gradient computation.

courant_number property 

courant_number: float

Calculate the Courant number for the simulation.

The Courant number is a dimensionless quantity that determines stability of the FDTD simulation. It represents the ratio of the physical propagation speed to the numerical propagation speed.

Returns:
  • float( float ) –

    The Courant number, scaled by the courant_factor and normalized for 3D simulations.

invertible_optimization property 

invertible_optimization: bool

Check if invertible optimization is enabled.

Invertible optimization uses time-reversibility of Maxwell's equations to compute gradients with reduced memory requirements compared to checkpointing-based methods.

Returns:
  • bool( bool ) –

    True if gradient computation uses invertible differentiation (recorder is specified), False otherwise.

max_travel_distance property 

max_travel_distance: float

Calculate the maximum distance light can travel during the simulation.

This represents the theoretical maximum distance that light could travel through the simulation volume, useful for determining if the simulation time is sufficient for light to traverse the entire domain.

Returns:
  • float( float ) –

    Maximum travel distance in meters, based on the speed of light and total simulation time.

only_forward property 

only_forward: bool

Check if the simulation is forward-only (no gradient computation).

Forward-only simulations don't compute gradients and are used when only the forward propagation of electromagnetic fields is needed, without optimization.

Returns:
  • bool( bool ) –

    True if no gradient configuration is specified, False otherwise.

time_step_duration property 

time_step_duration: float

Calculate the duration of a single time step.

The time step duration is determined by the Courant condition to ensure numerical stability. It depends on the spatial resolution and the speed of light.

Returns:
  • float( float ) –

    Time step duration in seconds, calculated using the Courant condition and spatial resolution.

time_steps_total property 

time_steps_total: int

Calculate the total number of time steps for the simulation.

Determines how many discrete time steps are needed to simulate the specified total simulation time, based on the time step duration.

Returns:
  • int( int ) –

    Total number of time steps needed to reach the specified simulation time.