Caching file related information using info or hints?

John Wilson (jwilson@hal300.cs.colorado.edu)
Tue, 18 Jun 1996 08:48:48 -0600

I was considering sending the following regarding how would
a library writer cache file related information. Leslie
Hart's proposal for info arguements would permit this type
of operation. I do not think Rolf Rabenseifner's proposal
would permit this. It seems to me that some method
in the manner of MPI_Attr_put/get is needed for caching information
in file handles and that there is a natural synergy between this
problem and the situation with hints/info.

Here is what I had been planning on sending:

Is there a means in the MPI-IO proposal for caching information in/with
a file handle? I was pondering how I would write using MPI-IO a library
we are considering writing. One thought that came to mind was that
storing information associated with particular files would be easier if there
were a facility similar to MPI_Attr_put/get but for files. I was
pondering proposing such, when the thought of using MPI-IO hints came to
mind. However, I am uncertain this would work. Also, with
the proposed redefinition of from hints to an info structure, I was wondering
whether my idea would work with the change.

Basically my idea for caching information using hints is:
1. My library would use a hint name that does not start with MPI_ to
attempt to avoid conflicts.

2. The user would attach the hint using MPI_Open, MPI_Fcntl as with
a hint to MPI-IO

3. In my library I would retrieve the hints using MPI_Fcntl.

Would this work based on the proposed standard and could I do something
similar using the info structure?

John Wilson