[petsc-users] portability question for reduce operations

[Barry Smith]

> On Apr 10, 2015, at 4:31 PM, Jed Brown <jed at jedbrown.org> wrote:
> 
> Ed Bueler <elbueler at alaska.edu> writes:
>> option 1. full use of MPIU_ types and ops:
>> 
>> PetscReal     x, xloc;
>> PetscInt        n, nloc;
>> MPI_Allreduce(&xloc,&x,1,MPIU_REAL,MPIU_SUM,comm);
>> MPI_Allreduce(&nloc,&n,1,MPIU_INT,MPIU_SUM,comm);
> 
> Use MPI_SUM for integer types.  MPIU_SUM is for real/scalar types.

   With Satish's cleanup of basic type names and organization we should fix this so users don't get bitten by the inconsistency.

   It's a pity MPI didn't provide a way to incrementally add new types for already defined Op.

  Barry