NAME

       MPI_File_set_atomicity - Sets consistency semantics for data-access operations (collective).

SYNTAX

C Syntax

       #include <mpi.h> int MPI_File_set_atomicity(MPI_File fh, int flag)

Fortran Syntax

       USE MPI
       ! or the older form: INCLUDE 'mpif.h'
       MPI_FILE_SET_ATOMICITY(FH, FLAG, IERROR)
            INTEGER   FH, FLAG, IERROR

C++ Syntax

       #include <mpi.h>
       void MPI::File::Set_atomicity(bool flag)

INPUT PARAMETERS

       fh        File handle (handle).

       flag      true to enable atomic mode, false to enable nonatomic mode (boolean).

OUTPUT PARAMETER

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       The  consistency  semantics  for  data-access  operations  using  the  set of file handles created by one
       collective MPI_File_open is set by collectively calling  MPI_File_set_atomicity.  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.

       The default value on a call to MPI_File_open in Open MPI is true for jobs running on more than one  node,
       false for jobs running on a single SMP. For more information, see the MPI-2 standard.

ERRORS

       Almost  all  MPI  routines  return  an  error  value; C routines as the value of the function and Fortran
       routines in the last argument. C++ functions do not return errors. If the default error handler is set to
       MPI::ERRORS_THROW_EXCEPTIONS,  then  on  error  the  C++  exception  mechanism  will  be used to throw an
       MPI::Exception object.

       Before the error value is returned, the current MPI error handler is called. For MPI I/O function errors,
       the  default  error  handler  is  set  to  MPI_ERRORS_RETURN.  The  error  handler  may  be  changed with
       MPI_File_set_errhandler; the predefined error handler MPI_ERRORS_ARE_FATAL may be used to make I/O errors
       fatal. Note that MPI does not guarantee that an MPI program can continue past an error.