MPI_File_preallocate - Preallocates a specified amount of storage space at the beginning of a file (collective).
22.214.171.124.1. C Syntax
#include <mpi.h> int MPI_File_preallocate(MPI_File fh, MPI_Offset size)
126.96.36.199.2. Fortran Syntax
USE MPI ! or the older form: INCLUDE 'mpif.h' MPI_FILE_PREALLOCATE(FH, SIZE, IERROR) INTEGER FH, IERROR INTEGER(KIND=MPI_OFFSET_KIND) SIZE
188.8.131.52.3. Fortran 2008 Syntax
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
184.108.40.206. INPUT/OUTPUT PARAMETER
fh: File handle (handle).
220.127.116.11. INPUT PARAMETER
size: Size to preallocate file, in bytes (integer).
18.104.22.168. OUTPUT PARAMETER
ierror: Fortran only: Error status (integer).
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.
When using the collective routine MPI_File_set_size on a UNIX file, if the size that is set is smaller than the current file size, the file is truncated at the position defined by size. If the size is set to be larger than the current file size, the file size becomes the set size. When the file size is increased this way with MPI_File_set_size, new regions are created in the file with displacements between the old file size and the larger, newly set file size.
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.
Almost all MPI routines return an error value; C routines as the return result of the function and Fortran routines in the last argument.
Before the error value is returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) is called. If no communication object is associated with the MPI call, then the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler. When MPI_COMM_SELF is not initialized (i.e., before MPI_Init/MPI_Init_thread, after MPI_Finalize, or when using the Sessions Model exclusively) the error raises the initial error handler. The initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_Comm_spawn/MPI_Comm_spawn_multiple. If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all other MPI functions.
Open MPI includes three predefined error handlers that can be used:
MPI_ERRORS_ARE_FATALCauses the program to abort all connected MPI processes.
MPI_ERRORS_ABORTAn error handler that can be invoked on a communicator, window, file, or session. When called on a communicator, it acts as if MPI_Abort was called on that communicator. If called on a window or file, acts as if MPI_Abort was called on a communicator containing the group of processes in the corresponding window or file. If called on a session, aborts only the local process.
MPI_ERRORS_RETURNReturns an error code to the application.
MPI applications can also implement their own error handlers by calling:
Note that MPI does not guarantee that an MPI program can continue past an error.
See the Error Handling section of the MPI-3.1 standard for more information.