Dear implementers of MPI-3.0 MPI_WIN_ALLOCATE_SHARED, my question is not about the Interface, but on the implementations: If a set of MPI processes within a shared memory node and Communicator wants to allocate a shared memory window: - Are there similar limits as if a set of threads wants to allocate memory and use it as global Memory by all threads, i.e., is it possible to allocate most physical memory with MPI_WIN_ALLOCATE_SHARED? - Is there an additional restriction on the number of shared memory windows? - Is there an additional restriction if one process defines the whole size as window size and all other processes within the SMP node use size=0? - Do you know other restrictions if I want to substitute OpenMP (not OpenMPI!) by shared memory MPI programming, i.e. hybrid MPI+MPI instead of hybrid MPI+OpenMP? Is your answer generally valid for mpich and OpenMPI and must I expect some additional restrictions on some vendor's MPIs? It is about the real implementations, e.g. in mpich and OpenMPI, but I expect that our MPI-3 RMA working group knows the answer. Best regards Rolf -- Dr. Rolf Rabenseifner . . . . . . . . . .. email [email protected] High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530 University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832 Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room 1.307)