[Carpet] checkpoint at run-time request

[Bela Szilagyi]

Every once in a while (e.g., five minutes ago) I find myself guilty of not 
having requested checkpoint files at a large enough frequency.

In other terms, my current run may die before getting to its first check-point 
file.  It will check-point at termination, but this data may not be good for 
restarting another run with a "fix".

The question comes -- would it be possible to add some feature that would 
allow me to tell a running simulation -- "please dump a checkpoint, then go 
on."  The ordinary solution would be having Cactus watch a file in which the 
user can place the request...  I know there is the web-interface option of 
steering parameters, but I never trusted that enough to try...

Could one just send a signal of some sort to the running code and have the 
checkpoint file be dumped?

More generically, it would be quite useful to have a simple, usable, and 
trustworthy way of modifying parameters of a run, while it's running.  Say, 
again, a simple ascii file being watched, read, parsed at every so many 
iterations...



-- 
Bela Szilagyi

Max-Planck-Institut für Gravitationsphysik
Albert-Einstein-Institut
Tel: +49 331 567 7632
Fax: +49 331 567 7649