Its not part of MPI because the eager limit is an implementation choice that is not part of the standard, and not all MPI implementations have had such limits.  MPI_T is exactly for stuff that isn't part of the standard but may be a useful part of a particular implementation.

Bill

William Gropp
Director, Parallel Computing Institute
Deputy Director for Research
Institute for Advanced Computing Applications and Technologies
Thomas M. Siebel Chair in Computer Science
University of Illinois Urbana-Champaign




On Oct 24, 2013, at 5:31 PM, Junchao Zhang wrote:

I would call it "selective MPI parameter setting". 
But users need to know to what extent the size is "slightly larger", and be notified doing so is indeed better.
BTW, I'm confused if this case often happens, why not implement it in MPI instead of bothering MPI_T?