[Developers] Steering checkpointing by wall time

[Thomas Radke]

Erik Schnetter wrote:
> I suggest to add a new parameter to CactusBase/IOUtil which  
> checkpoints every so many wall clock hours.  This is often more  
> convenient than choosing the checkpointing interval by iterations.

Sounds good to me.

I presume users will know that a checkpoint will be triggered if either 
of the checkpoint conditions IO::checkpoint_every or 
IO::checkpoint_every_walltime_hours is met.
For completeness we should either make the new parameter known to all 
I/O thorns which support checkpointing, or at least document that they 
don't support it.

-- 
Cheers, Thomas.