MPI_File_preallocate - Preallocates storage space for a
file
SYNOPSIS
C:
#include "mpi.h"
int MPI_File_preallocate(MPI_File fh, MPI_Offset size)
Fortran:
INCLUDE "mpif.h" (or USE MPI)
INTEGER fh, ierror
INTEGER(KIND=MPI_OFFSET_KIND) size
CALL MPI_FILE_PREALLOCATE(fh, size, ierror)
DESCRIPTION
MPI_File_preallocate ensures that storage space is
allocated for the first size bytes of the file associated
with fh.
The MPI_File_preallocate routine accepts the following
arguments:
fh Specifies the file handle (handle)
size Specifies the size to preallocate (nonnegative
integer)
ierror Specifies the return code value for successful
completion, which is in MPI_SUCCESS.
MPI_SUCCESS is defined in the mpif.h file.
MPI_File_preallocate is collective; all processes in the
group must pass identical values for size. Regions of the
file that have been written previously are unaffected.
For newly allocated regions of the file,
MPI_File_preallocate has the same effect as writing
undefined data. If size is larger than the current file
size, the file size increases to size. If size is less
than or equal to the current file size, the file size is
unchanged.
The treatment of file pointers, pending nonblocking
accesses, and file consistency is the same as with
MPI_File_set_size. If MPI_MODE_SEQUENTIAL mode was
specified when the file was opened, it is erroneous to
call this routine.
expensive.
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_File_set_size(3), MPI_IO(3)
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