[petsc-dev] new P^1.5 algorithm in VecAssembleBegin?

[Barry Smith]

> On May 29, 2015, at 2:56 PM, Jed Brown <jed at jedbrown.org> wrote:
> 
> Mark Adams <mfadams at lbl.gov> writes:
>> Yea, I realized that VecAssembly should see this load imbalance unless it
>> had a barrier before its timer.  So I'm not sure what is going on.
> 
> Since you don't have any outgoing entries, I think the huge
> MPI_Allreduce is expensive.  No surprise.

   This explanation matches the known information.