[petsc-users] A bad commit affects MOOSE

[Jed Brown]

Derek Gaston <friedmud at gmail.com> writes:

> Sounds great to me - what library do I download that we're all going to use
> for managing the memory pool?  :-)
>
> Seriously though: why doesn't MPI give us an ability to get unique tag IDs
> for a given communicator?  

It's called a dup'd communicator.

> I like the way libMesh deals with this:
> https://github.com/libMesh/libmesh/blob/master/include/parallel/parallel_implementation.h#L1343

PETSc does something similar, but using attributes inside the MPI_Comm
instead of as a wrapper that goes around the communicator.

https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PetscCommGetNewTag.html

> I would definitely sign on for all of us to use the same library for
> getting unique tag IDs... and then we would need a lot less communicators...

Communicators should be cheap.  One per library per "size" isn't a huge
number of communicators.