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C Syntax #include <mpi.h> int MPI_File_preallocate(MPI_File fh, MPI_Offset size)
USE MPI ! or the older form: INCLUDE ’mpif.h’ MPI_FILE_PREALLOCATE(FH, SIZE, IERROR) INTEGER FH, IERROR INTEGER(KIND=MPI_OFFSET_KIND) SIZE
USE mpi_f08 MPI_File_preallocate(fh, size, ierror) TYPE(MPI_File), INTENT(IN) :: fh INTEGER(KIND=MPI_OFFSET_KIND), INTENT(IN) :: size INTEGER, OPTIONAL, INTENT(OUT) :: ierror
MPI_File_preallocate is collective; all processes in the group must pass identical values for size. Regions of the file that have previously been written 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.
INTEGER*MPI_OFFSET_KIND SIZE
where MPI_OFFSET_KIND is a constant defined in mpif.h and gives the length of the declared integer in bytes.
Sun MPI I/O does not necessarily allocate file space for such new regions. You may reserve file space either by using MPI_File_preallocate or by performing a read or write to certain bytes.
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.