[MPI3 Fortran] Deprecate mpif.h?

[Jeff Squyres]

On Mar 5, 2010, at 10:26 PM, Supalov, Alexander wrote:

> In the meantime, the feedback I'm getting across a wide commercial  
> ISV range is that a backward incompatible MPI-3 will be a major  
> issue for them.
>

I'm curious to know *EXACTLY* what you asked them, and how they  
understood the question.

Analogous example: if you ask someone, "Should I hit John?", they'll  
undoubtedly answer "NO!"  But if you leave out the context that you're  
the dealer in a blackjack game and John only has 2 cards that total a  
face value of 5, then they're not getting all the relevant information  
to answer the question properly.

> Moreover, those who include mpif.h now won't move until they see  
> MPI-3 offering compelling value.
>

And that's a perfectly reasonable approach.  What's the problem?

> "Survey data points (with the usual disclaimers)
>
>  Only 16% think recompiling to MPI-3 is bad: Good!
>  Only 11% willing to change source code to MPI-3: Boo!"
>
> I.e., with all the necessary reservations, we may have about 11% of  
> users who would be willing to add the MPI-3 features to their code.
>

*** NO!!! ***

This is NOT what the survey says.  That is NOT what the question asked.

The question asked if they wanted to move their application to an  
MPI-3 implementation -- it did NOT ask anything about using new MPI-3  
functionality.  Implying that this question has anything to do with  
people's intentions to using new MPI-3 functionality is just plain  
wrong.

> Further in the same slide we see (again in Jeff's words):
>
> "Do we care:
>  Running MPI-3 codes in MPI-1/2 implementations
>        I don’t think so
>  Integrating MPI-3 features in existing MPI-1/2 codes
>        I DO think so
>  Run MPI-1/2 codes without source code changes in MPI-3
>        YES (per survey data)"
>
> This, again with all the necessary reservations, indicates that  
> users directly ask us not to break the backward compatibility.
>

Q: Who has said anything about breaking backwards compatibility?
A: Only Alexander Supalov.

No one else intends to break backwards compatibility.  I don't know  
why you keep harping on a point that simply is not true.

This is what is so frustrating in this email thread and really brings  
my blood to a boil.  You are totally taking things out of context and  
leaving out details.

> From this, I derive that the desire to introduce a new, backward  
> incompatible MPI-3 Fortran interface may go against the overwhelming  
> user will for backward compatibility (89% above), as may the desire  
> to deprecate or freeze the conventional mpif.h and the mpi module.
>

Both of those conclusions are totally unsubstantiated by the survey  
data.

As has been said many times on this thread, your premise of removing  
mpif.h and use mpi is just plain wrong.  They're not going away.   
Period.  Stop saying that they are.

--
Jeff Squyres
jsquyres at cisco.com
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