Hints specified via info
(see Section 4.10, page )
allow a user to provide information
such as
file access patterns and file system specifics
to direct optimization.
Providing hints may enable an implementation to deliver
increased I/O performance or minimize the use of system resources.
However, hints do not change the semantics of any of the I/O interfaces.
In other words, an implementation is free to ignore all hints.
Hints are specified on a per file basis,
in MPI_FILE_OPEN, MPI_FILE_DELETE,
MPI_FILE_SET_VIEW, and MPI_FILE_SET_INFO,
via the opaque info object.
int MPI_File_set_info(MPI_File fh, MPI_Info info)
MPI_FILE_SET_INFO(FH, INFO, IERROR)INTEGER FH, INFO, IERROR
int MPI::File::Set_info(const MPI::Info& info)
void
MPI_FILE_SET_INFO sets new values for the hints of the file associated with fh. MPI_FILE_SET_INFO is a collective routine. The info object may be different on each process, but any info entries that an implementation requires to be the same on all processes must appear with the same value in each process's info object.
MPI_FILE_GET_INFO(fh, info_used)
int MPI_File_get_info(MPI_File fh, MPI_Info *info_used)
MPI_FILE_GET_INFO(FH, INFO_USED, IERROR)INTEGER FH, INFO_USED, IERROR
int MPI::File::Get_info() const
MPI::Info
MPI_FILE_GET_INFO returns a new info object containing the hints of the file associated with fh. The current setting of all hints actually used by the system related to this open file is returned in info_used. The user is responsible for freeing info_used via MPI_INFO_FREE.