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

[Barry Smith]

  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,
>> 
>