[Users] logic of scheduling SelectBoundConds in McLachlan?

Roland Haas roland.haas at physics.gatech.edu
Fri Feb 15 23:38:42 CST 2013

Hello Bernard,

> Hi. Can someone explain to me why ML_BSSN calls SelectBoundConds within
> MoL_PostStep? It seems like the kind of once-off routine that would happen
> near the start of a simulation, rather than something that has to be
> performed every single timestep.
In the "new" boundary/symmetry interface (ie using thorn Boundary and
Symbase) one has to Select the variables for boundaries each time before
ApplyBCs is scheduled. There is a routine in Boundaries that clears the

> I wouldn't mind, but while trying to understand why ML_BSSN was evolving
> so slowly on one of our machines, I looked at the TimerReport files, and
> saw that SelectBoundConds was taking *much* more time (like 20 times as
> long) than the actual RHS calculation routines.
The long time is most likely caused by the fact that the boundary
selection routine tends to be the one calling SYNC which means it is the
one that does an MPI wait (if there is load imbalance) and communicates
data for buffer zone prolongation etc.


My email is as private as my paper mail. I therefore support encrypting
and signing email messages. Get my PGP key from http://keys.gnupg.net.

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 262 bytes
Desc: OpenPGP digital signature
Url : http://lists.einsteintoolkit.org/pipermail/users/attachments/20130215/55f02bbc/attachment.bin 

More information about the Users mailing list