[petsc-dev] ugly shit

[Barry Smith]

On Nov 10, 2011, at 3:42 PM, Jed Brown wrote:

> On Thu, Nov 10, 2011 at 15:37, Barry Smith <bsmith at mcs.anl.gov> wrote:
> Actually I do find a partially implemented MPI_IN_PLACE in mpiuni
> 
>    I have finished the implementation in MPIUni and modified MPI.py to indicate MPI_IN_PLACE in mpiuni
> 
> Does this mean that we can rely on MPI_IN_PLACE being available?

   You could have ./configure check for MPI_IN_PLACE and generate an error if it doesn't exist.  But do we want to say PETSc requires MPI 2.0 (or at least parts of it)????  Since we already have support for not having MPI_IN_PLACE I'd only like to remove that extra support if we knew that all (sane) users had access to MPI_IN_PLACE. Do we know this?


> In general, can we rely on any MPI-2.0 features that have been implemented in mpiuni and remove the macro checking?

    I don't have a clue what parts of MPI-2.0 that MPIUni does or does not support :-(.  I'm afraid we'll need to find out one operation at a time. It definitely doesn't have the one-sided stuff, can/should that be added? I don't see a big upside in putting the one-sided stuff into MPI uni.


   Barry