[petsc-users] Should I synchronize processes explicitly, for instance using MPI_Barrier?

[Matthew Knepley]

On Fri, Aug 16, 2013 at 2:11 AM, Cong Li <solvercorleone at gmail.com> wrote:

> Hi
>
> I am a rookie to PETSc, and I am wondering about whether I should call
> MPI_Barrier to explicitly synchronize processes between PETSc calls.
> For example, a piece of code like below
>
>   ierr = MatMult(A,x,Ax); CHKERRQ(ierr);
>   ierr = VecWAXPY(r, neg_one, Ax, b);CHKERRQ(ierr);
>
> Should I add MPI_Barrier inbetween MatMult call and VecWAXPY call ?
>

No

   Matt


> My guess is that it is unnecessary. However, I am not so confident in this
> guess, for I don't have much experience on using PETSc.
>
> Thanks in advance.
>
> Cong Li
>



-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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