Folks,

Does someone remember why we disallowed users from calling MPI_Request_free on 
nonblocking collective requests?  I remember the reasoning for not allowing 
cancel (i.e., the operation might have completed on some processes, but not 
all), but not for Request_free.  AFAICT, allowing the users to free the request 
doesn’t make any difference to the MPI library.  The MPI library would simply 
maintain its own refcount to the request and continue forward till the 
operation completes.  One of our users would like to free NBC requests so they 
don’t have to wait for the operation to complete in some situations.

Unfortunately, when I added the Rput/Rget operations in the RMA chapter, I 
copy-pasted that text into RMA as well without thinking too hard about it.  My 
bad!  Either the RMA committee missed it too, or they thought of a reason that 
I can’t think of now.

Can someone clarify or remind me what the reason was?

Regards,

  — Pavan

MPI-3.1 standard, page 197, lines 26-27:

“It is erroneous to call MPI_REQUEST_FREE or MPI_CANCEL for a request 
associated with a nonblocking collective operation.”

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