SpECTRE  v2024.08.03
Public Member Functions | Public Attributes | List of all members
TimeStepRequest Struct Reference

Information on a requested time-step size returned by StepChoosers. More...

#include <TimeStepRequest.hpp>

Public Member Functions

void pup (PUP::er &p)
 

Public Attributes

std::optional< double > size_goal {}
 
std::optional< double > size {}
 
std::optional< double > end {}
 
std::optional< double > size_hard_limit {}
 
std::optional< double > end_hard_limit {}
 

Detailed Description

Information on a requested time-step size returned by StepChoosers.

Requests made using this struct control most of the changing of slab and local-time-stepping step sizes. Slab-size changing is more complex, as it is controlled using the ChangeSlabSize event, which may run zero or more times per slab, and may have the application of its result delayed. The step size for LTS is adjusted using a constant list of StepChoosers on every step.

For slab-size adjustment (including the global time step when not using LTS), a "goal" step size is maintained from step to step. It is initially the initial slab size from the input file, and can be adjusted by any request setting the size_goal field of this struct. If multiple requests set new goals at the same time, the smallest value is used. At the start of each slab, the size is chosen to be the smallest of the current goal and the temporary limits imposed by any requests processed at that time. For the LTS step size, the current step size is used as the goal if no request sets a new one.

Any request with either the size or end fields set introduces a temporary step size limit. If only one of the two is set, the chosen step size will be limited to be not larger than *size, or not go beyond the time *end. If both are set, the tighter limit may be ignored if the looser limit is chosen as the actual step, but the step will not be chosen to be intermediate between two temporary limits from the same request object.

The hard limits are not used in setting the step size, but if the actual step does not satisfy all hard limits from all requests the evolution will be terminated with an error.

Note
All step sizes are subject to roundoff error in either direction except for two cases:
  • Slab sizes imposed by the end limit of a request will always end precisely at the requested time.
  • LTS step sizes within a single slab will always be considered to have size ratios that are exactly powers of two for the purposes of the size_goal and size limits.
The documentation for this struct was generated from the following file: