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MPI_File_iwrite_at(3) man page (version 1.8.1)

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Name

MPI_File_iwrite_at - Writes a file at an explicitly specified offset (nonblocking, noncollective).

Syntax


C Syntax
    #include <mpi.h>
    int MPI_File_iwrite_at(MPI_File fh, MPI_Offset offset,
          const void *buf, int count, MPI_Datatype datatype, MPI_Request *request)

Fortran Syntax (see FORTRAN 77 NOTES)


    INCLUDE ’mpif.h’
    MPI_FILE_IWRITE_AT(FH, OFFSET, BUF, COUNT, DATATYPE, REQUEST, IERROR)
            <type> BUF(*)
            INTEGER    FH, COUNT, DATATYPE, REQUEST, IERROR
        INTEGER(KIND=MPI_OFFSET_KIND) OFFSET

C++ Syntax


#include <mpi.h>
MPI::Request MPI::File::Iwrite_at(MPI::Offset offset, const void* buf,
    int count, const MPI::Datatype& datatype)

Input/Output Parameter

fh
File handle (handle).

Input Parameters

offset
File offset (integer).
buf
Initial address of buffer (choice).
count
Number of elements in buffer (integer).
datatype
Data type of each buffer element (handle).

Output Parameters

request
Request object (handle).
IERROR
Fortran only: Error status (integer).

Description

MPI_File_iwrite_at is a nonblocking version of MPI_File_write_at. It attempts to write into the file associated with fh (at the offset position) a total number of count data items having datatype type from the user’s buffer buf. The offset is in etype units relative to the current view. That is, holes are not counted when locating an offset. The data is written into those parts of the file specified by the current view. MPI_File_iwrite_at stores the number of datatype elements actually written in status. All other fields of status are undefined. The request structure can be passed to MPI_Wait or MPI_Test, which will return a status with the number of bytes actually accessed.

It is erroneous to call this function if MPI_MODE_SEQUENTIAL mode was specified when the file was open.

Fortran 77 Notes

The MPI standard prescribes portable Fortran syntax for the OFFSET argument only for Fortran 90. FORTRAN 77 users may use the non-portable syntax


     INTEGER*MPI_OFFSET_KIND OFFSET

where MPI_OFFSET_KIND is a constant defined in mpif.h and gives the length of the declared integer in bytes.

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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