MPI_File_set_atomicity - Sets the atomicity mode


SYNOPSIS

       C:

            #include "mpi.h"

            int MPI_File_set_atomicity(MPI_File fh, int flag)

       Fortran:

            INCLUDE "mpif.h" (or USE MPI)

            INTEGER fh, ierror
            LOGICAL flag

            CALL MPI_FILE_SET_ATOMICITY(fh, flag, ierror)


DESCRIPTION

       MPI_File_set_atomicity sets the atomicity mode.  Let fh be
       the set of file handles created by one collective open
       operation. This routine accepts the following arguments:

       fh        Specifies the file handle (handle)

       flag      Indicates true to set atomic mode, false to set
                 nonatomic mode (logical)

       ierror    Specifies the return code value for successful
                 completion, which is in MPI_SUCCESS.
                 MPI_SUCCESS is defined in the mpif.h file.

       You can set the consistency semantics for data access
       operations that use fh by collectively calling
       MPI_File_set_atomicity on fh.  MPI_File_set_atomicity is
       collective; all processes in the group must pass identical
       values for fh and flag.  If flag is true, atomic mode is
       set; if flag is false, nonatomic mode is set.

       Changing the consistency semantics for an open file
       affects only new data accesses.  All completed data
       accesses are guaranteed to abide by the consistency
       semantics in effect during their execution.  Nonblocking
       data accesses and split collective operations that have
       not completed (for example, because of MPI_WAIT) are
       guaranteed to abide only by nonatomic mode consistency
       semantics.

       Because the semantics guaranteed by atomic mode are
       stronger than those guaranteed by nonatomic mode, an
       implementation is free to adhere to the more stringent


   Notes for Fortran
       All MPI objects (for example, MPI_Datatype, MPI_Comm,
       MPI_File) are of type INTEGER.


SEE ALSO

       MPI_File_open(3), MPI_IO(3)


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