MPI_File_read_at(3) Open MPI MPI_File_read_at(3)
NAME
MPI_File_read_at - Reads a file at an explicitly specified offset
(blocking, noncollective).
SYNTAX
C Syntax
#include <mpi.h>
int MPI_File_read_at(MPI_File fh, MPI_Offset offset,
void *buf, int count, MPI_Datatype datatype,
MPI_Status *status)
Fortran Syntax (see FORTRAN 77 NOTES)
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_FILE_READ_AT(FH, OFFSET, BUF, COUNT,
DATATYPE, STATUS, IERROR)
<type> BUF(*)
INTEGER FH, COUNT, DATATYPE, STATUS(MPI_STATUS_SIZE), IERROR
INTEGER(KIND=MPI_OFFSET_KIND) OFFSET
Fortran 2008 Syntax
USE mpi_f08
MPI_File_read_at(fh, offset, buf, count, datatype, status, ierror)
TYPE(MPI_File), INTENT(IN) :: fh
INTEGER(KIND=MPI_OFFSET_KIND), INTENT(IN) :: offset
TYPE(*), DIMENSION(..) :: buf
INTEGER, INTENT(IN) :: count
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Status) :: status
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
C++ Syntax
#include <mpi.h>
void MPI::File::Read_at(MPI::Offset offset, void* buf,
int count, const MPI::Datatype& datatype,
MPI::Status& status)
void MPI::File::Read_at(MPI::Offset offset, void* buf,
int count, const MPI::Datatype& datatype)
INPUT PARAMETERS
fh File handle (handle).
offset File offset (integer).
count Number of elements in buffer (integer).
datatype Data type of each buffer element (handle).
OUTPUT PARAMETERS
buf Initial address of buffer (choice).
status Status object (status).
IERROR Fortran only: Error status (integer).
DESCRIPTION
MPI_File_read_at attempts to read from the file associated with fh (at
the offset position) a total number of count data items having datatype
type into 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 taken out of those parts of the file specified by
the current view. MPI_File_read_at stores the number of datatype ele-
ments actually read in status. All other fields of status are unde-
fined. It is erroneous to call this function if MPI_MODE_SEQUENTIAL
mode was specified when the file was opened.
FORTRAN 77 NOTES
The MPI standard prescribes portable Fortran syntax for the OFFSET ar-
gument 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++ func-
tions 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_ER-
RORS_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.
4.1.2 Nov 24, 2021 MPI_File_read_at(3)
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