Checkpointing Invocation

Thorns register their checkpointing routines at CCTK_CPINITIAL and/or CCTK_CHECKPOINT and/or CCTK_TERMINATE. These time bins are scheduled right after all initial data has been set up, after every evolution timestep, and after the last time step of a simulation, respectively. (See Section B3.3.4 for a description of all timebins). Depending on parameter settings, the checkpoint routines decide whether to write an initial data checkpoint, and when to write an evolution checkpoint.

Each checkpoint routine should save all information to persistent storage, which is necessary to restart the simulation at a later time from exactly the same state. Such information would include

• the current settings of all parameters
• the contents of all grid variables which have global storage assigned and are not tagged with checkpoint="no" (see also Section E2.2.4 on page for a list of possible tags)
  Note that grid variables should be synced before writing them to disk.
• other relevant information such as the current iteration number and physical time, the number of processors, etc.