MPI_File_preallocate(3)MPI_File_preallocate(3)NAMEMPI_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)
DESCRIPTIONMPI_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.
In some implementations, file preallocation might be expensive.
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MPI_File_preallocate(3)MPI_File_preallocate(3)
Notes for Fortran
All MPI objects (for example, MPI_Datatype, MPI_Comm, MPI_File) are of
type INTEGER.
SEE ALSOMPI_File_open(3), MPI_File_set_size(3), MPI_IO(3)
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