MPI_UNIQUE_OPEN
Rajeev Thakur (thakur@mcs.anl.gov)
Wed, 9 Apr 1997 18:04:43 -0500
The MPI_UNIQUE_OPEN amode allows a user to specify that
the file will not be concurrently opened by another different
collective open call anywhere or by some other application. This
knowledge allows the implementation to optimize accesses to the
file. For example, file caching and maintaining consistency among
caches become much easier if the implementation is assured that no
other processes other than the ones involved in this collective open
will be accessing the file. It can also eliminate the need for file
locking.
I expect this mode of access to be the common case in real
applications. I also expect that application programmers will forget
to specify the MPI_UNIQUE_OPEN mode, thereby preventing optimizations.
Therefore, I would like MPI_UNIQUE_OPEN to be the default for any
open. MPI_Open should instead provide an amode called
MPI_NONUNIQUE_OPEN that specifically indicates that the file may be
opened elsewhere.
This is somewhat similar to having non-atomic access mode as the
default.
Comments?
Rajeev