Ubuntu Manpage: MPI_Win_allocate_shared - Create an MPI Window object for one-sided communication and shared memory

NAME

       MPI_Win_allocate_shared  -   Create  an  MPI  Window object for one-sided communication and shared memory
       access, and allocate memory at each process

SYNOPSIS

       int MPI_Win_allocate_shared(MPI_Aint size, int disp_unit, MPI_Info info,
       MPI_Comm comm, void *baseptr, MPI_Win *win)

       int MPI_Win_allocate_shared_c(MPI_Aint size, MPI_Aint disp_unit, MPI_Info info,
       MPI_Comm comm, void *baseptr, MPI_Win *win)

INPUT PARAMETERS

       size   - size of local window in bytes (non-negative integer)
       disp_unit
              - local unit size for displacements, in bytes (positive integer)
       info   - info argument (handle)
       comm   - intra-communicator (handle)

OUTPUT PARAMETERS

baseptr
- address of local allocated window segment (choice)
win - window object returned by the call (handle)

This is a collective call executed by all processes in the group of comm. On each process i, it
allocates memory of at least size bytes that is shared among all processes in comm, and returns a
pointer to the locally allocated segment in baseptr that can be used for load/store accesses on
the calling process. The locally allocated memory can be the target of load/store accesses by
remote processes; the base pointers for other processes can be queried using the function
MPI_Win_shared_query .

The call also returns a window object that can be used by all processes in comm to perform RMA
operations. The size argument may be different at each process and size = 0 is valid. It is the
user's responsibility to ensure that the communicator comm represents a group of processes that
can create a shared memory segment that can be accessed by all processes in the group. The
allocated memory is contiguous across process ranks unless the info key alloc_shared_noncontig is
specified. Contiguous across process ranks means that the first address in the memory segment of
process i is consecutive with the last address in the memory segment of process i - 1. This may
enable the user to calculate remote address offsets with local information only.

THREAD AND INTERRUPT SAFETY

       This routine is thread-safe.  This means that this routine may be safely used by multiple threads without
       the need for any user-provided thread locks.  However, the routine is  not  interrupt  safe.   Typically,
       this  is  due to the use of memory allocation routines such as malloc or other non-MPICH runtime routines
       that are themselves not interrupt-safe.

NOTES FOR FORTRAN

       All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have an additional argument ierr at the
       end of the argument list.  ierr is an integer and has the same meaning as the return value of the routine
       in C.  In Fortran, MPI routines are subroutines, and are invoked with the call statement.

       All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in Fortran.

ERRORS

       All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error value; C routines as the value of  the
       function  and Fortran routines in the last argument.  Before the value is returned, the current MPI error
       handler is called.  By default, this error handler aborts the MPI job.  The error handler may be  changed
       with    MPI_Comm_set_errhandler   (for   communicators),   MPI_File_set_errhandler   (for   files),   and
       MPI_Win_set_errhandler (for RMA windows).  The MPI-1 routine MPI_Errhandler_set may be used but  its  use
       is  deprecated.   The  predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be
       returned.  Note that MPI does not guarantee that an MPI program can continue past an error; however,  MPI
       implementations will attempt to continue whenever possible.

       MPI_SUCCESS
              - No error; MPI routine completed successfully.
       MPI_ERR_ARG
              -  Invalid  argument.   Some  argument  is invalid and is not identified by a specific error class
              (e.g., MPI_ERR_RANK ).
       MPI_ERR_COMM
              - Invalid communicator.  A common error is to use a null communicator in a call (not even  allowed
              in MPI_Comm_rank ).
       MPI_ERR_DISP
              -
       MPI_ERR_INFO
              - Invalid Info
       MPI_ERR_SIZE
              -
       MPI_ERR_OTHER
              - Other error; use MPI_Error_string to get more information about this error code.