[Mpi-forum] MPI user survey

Christian Bell csbell at myri.com
Mon Nov 16 12:11:34 CST 2009

On Nov 16, 2009, at 11:55 AM, Jeff Hammond wrote:

> Can we completely ignore the performance-richness dichotomy and ask
> the following?
> "Would you benefit if the MPI Forum enhances and extends the existing
> one-sided operations?  That is, would you like to replace MPI
> two-sided calls in your code with one-sided ones and/or use MPI
> instead of another one-sided API (e.g. ARMCI)?"

Why not be frank and to the point:

The MPI Forum is currently investigating whether it is worthwhile  
supporting two RMA interfaces -- a feature-rich RMA interface and/or a  
performance-oriented interface with potentially more constraints.

a) I only care about performance-oriented RMA
b) I want RMA to implement a rich set of features at the cost of some  
c) I think supporting 2 interfaces is a must because...

I won't elaborate more here because my slant against a feature-rich  
RMA will start showing (if it hasn't already).

For the RMA folks:

FWIW, I think a new feature-rich RMA just gives users more ways to  
write bad programs and hints at a performance benefit that  
implementations may never actually deliver.  An all-encompassing RMA  
interface is a noble goal but it doesn't seem compatible with all the  
specialization that needs to happen to exploit newer architectures.   
RMA will always be a form of specialization so it better come with a  
large carrot for users to consider it.  I'd rather have a skinny and  
constrained RMA interface that has a fighting chance to deliver what  
it aims to provide.  What's wrong with labeling a performance-oriented  
interface with "DEPRECATED: BAD IDEA" in 5 years if it will have  
failed?  IMHO, it's no worse than banking on a feature-rich RMA  
interface that may (yet again) drown in apathy.

No disrespect is intended to those already working hard to come up  
with a complete feature-rich and performance-portable RMA, but I see  
too much pain for very little gain.

	. . christian

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