[Developers] synchronise all processors before aborting on parameter errors

[Thomas Radke]

Hi,

there exists a PARAM_CHECK bin in which thorns can schedule routines to 
check the consistency of parameters and have the run stopped (using 
CCTK_Abort) if there are errors.
Now Bela reported the problem that, for multi-processor simulations 
using certain Infiniband MPI implementations, the run would die 
prematurely because some processors call CCTK_Abort() earlier than 
others, and in the logfile one cannot easily find the real reason for 
the abort anymore.

Putting output buffer caching issues aside, the problem could be fixed 
by inserting a CCTK_Barrier() call in the flesh function 
CCTKi_FinaliseParamWarn(), just before it would check whether there were 
any (local) parameter errors and then call CCTK_Abort().

I guess this small performance penalty would be acceptable ? Or does 
someone have a better solution ?

-- 
Cheers, Thomas.