[petsc-users] any reasons to distinguish MPIU_SUM from MPI_SUM?

[Fande Kong]

Thanks, Barry, Satish,

But, is it possible to uniform the use of MPI_SUM and MPIU_SUM? For
example, we could let  a Petsc function just switch to a regular MPI_Reduce
or other function when using PetscInt. In other words, we need a wrapper. I
always use MPIU_INT in a MPI function  when using PetscInt. It is very
straightforward to use MPIU_SUM, MPIU_MAX so on, when thinking about we are
using MPIU_INT.

Thanks,

Fande Kong,

On Mon, Aug 17, 2015 at 6:18 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
>   It is crucial. MPI also doesn't provide sums for __float128 precision.
> But MPI does always provide sums for 32 and 64 bit integers so no need for
> MPIU_SUM for PETSC_INT
>
>
> > On Aug 17, 2015, at 5:49 PM, Satish Balay <balay at mcs.anl.gov> wrote:
> >
> > I think some MPI impls didn't provide some of the ops on MPI_COMPLEX
> > datatype.
> >
> > So petsc provides these ops for PetscReal i.e MPIU_SUM, MPIU_MAX,
> MPIU_MIN
> >
> > Satish
> >
> > On Mon, 17 Aug 2015, Fande Kong wrote:
> >
> >> Hi all,
> >>
> >> I was wondering why, in Petsc,  MPI_Reduce with PetscInt needs MPI_SUM
> >> meanwhile MPI_Reduce with PetscReal needs MPIU_SUM? Do we have any
> special
> >> reasons to distinguish them?
> >>
> >> Thanks,
> >>
> >> Fande Kong,
> >>
> >
>
>
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