15.4.3. Data Access with Individual File Pointers
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Next: Data Access with Shared File Pointers
Previous: Data Access with Explicit Offsets
MPI maintains one individual file pointer
per process per
file handle.
The current value of this pointer implicitly specifies
the offset in the data access routines described in this section.
These routines only use and update the individual file pointers
maintained by MPI.
The shared file pointer is not used nor updated.
The individual file pointer routines
have the same semantics as the data access with explicit offset routines
described in Section Data Access with Explicit Offsets,
with the following modification:
- the offset is defined to be the current value
of the MPI-maintained individual file pointer.
After an individual file pointer operation is initiated,
the individual file pointer is updated to point
to the next etype after the last one
that will be accessed.
The file pointer is updated relative to the current view of the file.
If MPI_MODE_SEQUENTIAL mode was specified when the file
was opened, it is erroneous to call the routines in this
section, with
the exception of MPI_FILE_GET_BYTE_OFFSET.
| MPI_FILE_READ(fh, buf, count, datatype, status) |
| INOUT fh | file handle (handle) |
| OUT buf | initial address of buffer (choice) |
| IN count | number of elements in buffer (integer) |
| IN datatype | datatype of each buffer element (handle) |
| OUT status | status object (status) |
C binding
int MPI_File_read(MPI_File fh, void *buf, int count, MPI_Datatype datatype, MPI_Status *status)
int MPI_File_read_c(MPI_File fh, void *buf, MPI_Count count, MPI_Datatype datatype, MPI_Status *status)
Fortran 2008 binding
MPI_File_read(fh, buf, count, datatype, status, ierror)
TYPE(MPI_File), INTENT(IN) :: fh
TYPE(*), DIMENSION(..) :: buf
INTEGER, INTENT(IN) :: count
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Status) :: status
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
MPI_File_read(fh, buf, count, datatype, status, ierror) !(_c)
TYPE(MPI_File), INTENT(IN) :: fh
TYPE(*), DIMENSION(..) :: buf
INTEGER(KIND=MPI_COUNT_KIND), INTENT(IN) :: count
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Status) :: status
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
Fortran binding
MPI_FILE_READ(FH, BUF, COUNT, DATATYPE, STATUS, IERROR)
INTEGER FH, COUNT, DATATYPE, STATUS(MPI_STATUS_SIZE), IERROR
<type> BUF(*)
MPI_FILE_READ reads a file using the individual file pointer.
Example
The following Fortran code fragment is an example of reading
a file until the end of file is reached:
| MPI_FILE_READ_ALL(fh, buf, count, datatype, status) |
| INOUT fh | file handle (handle) |
| OUT buf | initial address of buffer (choice) |
| IN count | number of elements in buffer (integer) |
| IN datatype | datatype of each buffer element (handle) |
| OUT status | status object (status) |
C binding
int MPI_File_read_all(MPI_File fh, void *buf, int count, MPI_Datatype datatype, MPI_Status *status)
int MPI_File_read_all_c(MPI_File fh, void *buf, MPI_Count count, MPI_Datatype datatype, MPI_Status *status)
Fortran 2008 binding
MPI_File_read_all(fh, buf, count, datatype, status, ierror)
TYPE(MPI_File), INTENT(IN) :: fh
TYPE(*), DIMENSION(..) :: buf
INTEGER, INTENT(IN) :: count
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Status) :: status
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
MPI_File_read_all(fh, buf, count, datatype, status, ierror) !(_c)
TYPE(MPI_File), INTENT(IN) :: fh
TYPE(*), DIMENSION(..) :: buf
INTEGER(KIND=MPI_COUNT_KIND), INTENT(IN) :: count
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Status) :: status
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
Fortran binding
MPI_FILE_READ_ALL(FH, BUF, COUNT, DATATYPE, STATUS, IERROR)
INTEGER FH, COUNT, DATATYPE, STATUS(MPI_STATUS_SIZE), IERROR
<type> BUF(*)
MPI_FILE_READ_ALL is a collective version
of the blocking MPI_FILE_READ interface.
| MPI_FILE_WRITE(fh, buf, count, datatype, status) |
| INOUT fh | file handle (handle) |
| IN buf | initial address of buffer (choice) |
| IN count | number of elements in buffer (integer) |
| IN datatype | datatype of each buffer element (handle) |
| OUT status | status object (status) |
C binding
int MPI_File_write(MPI_File fh, const void *buf, int count, MPI_Datatype datatype, MPI_Status *status)
int MPI_File_write_c(MPI_File fh, const void *buf, MPI_Count count, MPI_Datatype datatype, MPI_Status *status)
Fortran 2008 binding
MPI_File_write(fh, buf, count, datatype, status, ierror)
TYPE(MPI_File), INTENT(IN) :: fh
TYPE(*), DIMENSION(..), INTENT(IN) :: buf
INTEGER, INTENT(IN) :: count
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Status) :: status
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
MPI_File_write(fh, buf, count, datatype, status, ierror) !(_c)
TYPE(MPI_File), INTENT(IN) :: fh
TYPE(*), DIMENSION(..), INTENT(IN) :: buf
INTEGER(KIND=MPI_COUNT_KIND), INTENT(IN) :: count
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Status) :: status
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
Fortran binding
MPI_FILE_WRITE(FH, BUF, COUNT, DATATYPE, STATUS, IERROR)
INTEGER FH, COUNT, DATATYPE, STATUS(MPI_STATUS_SIZE), IERROR
<type> BUF(*)
MPI_FILE_WRITE writes a file using the individual file pointer.
| MPI_FILE_WRITE_ALL(fh, buf, count, datatype, status) |
| INOUT fh | file handle (handle) |
| IN buf | initial address of buffer (choice) |
| IN count | number of elements in buffer (integer) |
| IN datatype | datatype of each buffer element (handle) |
| OUT status | status object (status) |
C binding
int MPI_File_write_all(MPI_File fh, const void *buf, int count, MPI_Datatype datatype, MPI_Status *status)
int MPI_File_write_all_c(MPI_File fh, const void *buf, MPI_Count count, MPI_Datatype datatype, MPI_Status *status)
Fortran 2008 binding
MPI_File_write_all(fh, buf, count, datatype, status, ierror)
TYPE(MPI_File), INTENT(IN) :: fh
TYPE(*), DIMENSION(..), INTENT(IN) :: buf
INTEGER, INTENT(IN) :: count
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Status) :: status
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
MPI_File_write_all(fh, buf, count, datatype, status, ierror) !(_c)
TYPE(MPI_File), INTENT(IN) :: fh
TYPE(*), DIMENSION(..), INTENT(IN) :: buf
INTEGER(KIND=MPI_COUNT_KIND), INTENT(IN) :: count
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Status) :: status
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
Fortran binding
MPI_FILE_WRITE_ALL(FH, BUF, COUNT, DATATYPE, STATUS, IERROR)
INTEGER FH, COUNT, DATATYPE, STATUS(MPI_STATUS_SIZE), IERROR
<type> BUF(*)
MPI_FILE_WRITE_ALL is a collective version
of the blocking MPI_FILE_WRITE interface.
| MPI_FILE_IREAD(fh, buf, count, datatype, request) |
| INOUT fh | file handle (handle) |
| OUT buf | initial address of buffer (choice) |
| IN count | number of elements in buffer (integer) |
| IN datatype | datatype of each buffer element (handle) |
| OUT request | request object (handle) |
C binding
int MPI_File_iread(MPI_File fh, void *buf, int count, MPI_Datatype datatype, MPI_Request *request)
int MPI_File_iread_c(MPI_File fh, void *buf, MPI_Count count, MPI_Datatype datatype, MPI_Request *request)
Fortran 2008 binding
MPI_File_iread(fh, buf, count, datatype, request, ierror)
TYPE(MPI_File), INTENT(IN) :: fh
TYPE(*), DIMENSION(..), ASYNCHRONOUS :: buf
INTEGER, INTENT(IN) :: count
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Request), INTENT(OUT) :: request
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
MPI_File_iread(fh, buf, count, datatype, request, ierror) !(_c)
TYPE(MPI_File), INTENT(IN) :: fh
TYPE(*), DIMENSION(..), ASYNCHRONOUS :: buf
INTEGER(KIND=MPI_COUNT_KIND), INTENT(IN) :: count
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Request), INTENT(OUT) :: request
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
Fortran binding
MPI_FILE_IREAD(FH, BUF, COUNT, DATATYPE, REQUEST, IERROR)
INTEGER FH, COUNT, DATATYPE, REQUEST, IERROR
<type> BUF(*)
MPI_FILE_IREAD is a nonblocking version of the MPI_FILE_READ interface.
Example
The following Fortran code fragment illustrates file pointer
update semantics:
| MPI_FILE_IREAD_ALL(fh, buf, count, datatype, request) |
| INOUT fh | file handle (handle) |
| OUT buf | initial address of buffer (choice) |
| IN count | number of elements in buffer (integer) |
| IN datatype | datatype of each buffer element (handle) |
| OUT request | request object (handle) |
C binding
int MPI_File_iread_all(MPI_File fh, void *buf, int count, MPI_Datatype datatype, MPI_Request *request)
int MPI_File_iread_all_c(MPI_File fh, void *buf, MPI_Count count, MPI_Datatype datatype, MPI_Request *request)
Fortran 2008 binding
MPI_File_iread_all(fh, buf, count, datatype, request, ierror)
TYPE(MPI_File), INTENT(IN) :: fh
TYPE(*), DIMENSION(..), ASYNCHRONOUS :: buf
INTEGER, INTENT(IN) :: count
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Request), INTENT(OUT) :: request
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
MPI_File_iread_all(fh, buf, count, datatype, request, ierror) !(_c)
TYPE(MPI_File), INTENT(IN) :: fh
TYPE(*), DIMENSION(..), ASYNCHRONOUS :: buf
INTEGER(KIND=MPI_COUNT_KIND), INTENT(IN) :: count
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Request), INTENT(OUT) :: request
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
Fortran binding
MPI_FILE_IREAD_ALL(FH, BUF, COUNT, DATATYPE, REQUEST, IERROR)
INTEGER FH, COUNT, DATATYPE, REQUEST, IERROR
<type> BUF(*)
MPI_FILE_IREAD_ALL is a nonblocking version
of MPI_FILE_READ_ALL.
| MPI_FILE_IWRITE(fh, buf, count, datatype, request) |
| INOUT fh | file handle (handle) |
| IN buf | initial address of buffer (choice) |
| IN count | number of elements in buffer (integer) |
| IN datatype | datatype of each buffer element (handle) |
| OUT request | request object (handle) |
C binding
int MPI_File_iwrite(MPI_File fh, const void *buf, int count, MPI_Datatype datatype, MPI_Request *request)
int MPI_File_iwrite_c(MPI_File fh, const void *buf, MPI_Count count, MPI_Datatype datatype, MPI_Request *request)
Fortran 2008 binding
MPI_File_iwrite(fh, buf, count, datatype, request, ierror)
TYPE(MPI_File), INTENT(IN) :: fh
TYPE(*), DIMENSION(..), INTENT(IN), ASYNCHRONOUS :: buf
INTEGER, INTENT(IN) :: count
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Request), INTENT(OUT) :: request
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
MPI_File_iwrite(fh, buf, count, datatype, request, ierror) !(_c)
TYPE(MPI_File), INTENT(IN) :: fh
TYPE(*), DIMENSION(..), INTENT(IN), ASYNCHRONOUS :: buf
INTEGER(KIND=MPI_COUNT_KIND), INTENT(IN) :: count
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Request), INTENT(OUT) :: request
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
Fortran binding
MPI_FILE_IWRITE(FH, BUF, COUNT, DATATYPE, REQUEST, IERROR)
INTEGER FH, COUNT, DATATYPE, REQUEST, IERROR
<type> BUF(*)
MPI_FILE_IWRITE is a nonblocking version of MPI_FILE_WRITE.
| MPI_FILE_IWRITE_ALL(fh, buf, count, datatype, request) |
| INOUT fh | file handle (handle) |
| IN buf | initial address of buffer (choice) |
| IN count | number of elements in buffer (integer) |
| IN datatype | datatype of each buffer element (handle) |
| OUT request | request object (handle) |
C binding
int MPI_File_iwrite_all(MPI_File fh, const void *buf, int count, MPI_Datatype datatype, MPI_Request *request)
int MPI_File_iwrite_all_c(MPI_File fh, const void *buf, MPI_Count count, MPI_Datatype datatype, MPI_Request *request)
Fortran 2008 binding
MPI_File_iwrite_all(fh, buf, count, datatype, request, ierror)
TYPE(MPI_File), INTENT(IN) :: fh
TYPE(*), DIMENSION(..), INTENT(IN), ASYNCHRONOUS :: buf
INTEGER, INTENT(IN) :: count
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Request), INTENT(OUT) :: request
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
MPI_File_iwrite_all(fh, buf, count, datatype, request, ierror) !(_c)
TYPE(MPI_File), INTENT(IN) :: fh
TYPE(*), DIMENSION(..), INTENT(IN), ASYNCHRONOUS :: buf
INTEGER(KIND=MPI_COUNT_KIND), INTENT(IN) :: count
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Request), INTENT(OUT) :: request
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
Fortran binding
MPI_FILE_IWRITE_ALL(FH, BUF, COUNT, DATATYPE, REQUEST, IERROR)
INTEGER FH, COUNT, DATATYPE, REQUEST, IERROR
<type> BUF(*)
MPI_FILE_IWRITE_ALL is a nonblocking version
of MPI_FILE_WRITE_ALL.
| MPI_FILE_SEEK(fh, offset, whence) |
| INOUT fh | file handle (handle) |
| IN offset | file offset (integer) |
| IN whence | update mode (state) |
C binding
int MPI_File_seek(MPI_File fh, MPI_Offset offset, int whence)
Fortran 2008 binding
MPI_File_seek(fh, offset, whence, ierror)
TYPE(MPI_File), INTENT(IN) :: fh
INTEGER(KIND=MPI_OFFSET_KIND), INTENT(IN) :: offset
INTEGER, INTENT(IN) :: whence
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
Fortran binding
MPI_FILE_SEEK(FH, OFFSET, WHENCE, IERROR)
INTEGER FH, WHENCE, IERROR
INTEGER(KIND=MPI_OFFSET_KIND) OFFSET
MPI_FILE_SEEK updates the individual file pointer according to
whence,
which has the following possible values:
The offset can be negative, which allows seeking backwards.
It is erroneous to seek to a negative position in the view.
| MPI_FILE_GET_POSITION(fh, offset) |
| IN fh | file handle (handle) |
| OUT offset | offset of individual pointer (integer) |
C binding
int MPI_File_get_position(MPI_File fh, MPI_Offset *offset)
Fortran 2008 binding
MPI_File_get_position(fh, offset, ierror)
TYPE(MPI_File), INTENT(IN) :: fh
INTEGER(KIND=MPI_OFFSET_KIND), INTENT(OUT) :: offset
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
Fortran binding
MPI_FILE_GET_POSITION(FH, OFFSET, IERROR)
INTEGER FH, IERROR
INTEGER(KIND=MPI_OFFSET_KIND) OFFSET
MPI_FILE_GET_POSITION returns, in offset,
the current position of the individual file pointer in etype units
relative to the current view.
Advice to users.
The offset can be used in a future call to MPI_FILE_SEEK
using whence = MPI_SEEK_SET to return to the current position.
To set the displacement to the current file pointer position,
first convert offset into an absolute byte position using
MPI_FILE_GET_BYTE_OFFSET,
then call MPI_FILE_SET_VIEW with the resulting
displacement.
( End of advice to users.)
| MPI_FILE_GET_BYTE_OFFSET(fh, offset, disp) |
| IN fh | file handle (handle) |
| IN offset | offset (integer) |
| OUT disp | absolute byte position of offset (integer) |
C binding
int MPI_File_get_byte_offset(MPI_File fh, MPI_Offset offset, MPI_Offset *disp)
Fortran 2008 binding
MPI_File_get_byte_offset(fh, offset, disp, ierror)
TYPE(MPI_File), INTENT(IN) :: fh
INTEGER(KIND=MPI_OFFSET_KIND), INTENT(IN) :: offset
INTEGER(KIND=MPI_OFFSET_KIND), INTENT(OUT) :: disp
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
Fortran binding
MPI_FILE_GET_BYTE_OFFSET(FH, OFFSET, DISP, IERROR)
INTEGER FH, IERROR
INTEGER(KIND=MPI_OFFSET_KIND) OFFSET, DISP
MPI_FILE_GET_BYTE_OFFSET converts a view-relative offset
into an absolute byte position.
The absolute byte position (from the beginning of the file)
of offset relative to the current view of fh
is returned in disp.
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