MPI_File_set_atomicity(3) 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

    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.

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