[mpich-devel] datatype accessors with uncommited datatypes

[Jeff Hammond]

> On 12/27/2012 02:05 PM US Central Time, William Gropp wrote:
>> The standard is already clear - commit is only required when the
>> datatype is used for communication.  It is unnecessary for the
>> standard to list all cases where commit is not required - it is
>> enough to list where commit *is* required, which it does.

This is argument of the form "unless something is explicitly
prohibited, it is permitted," which is extraordinarily dangerous and
inconsistent with a robust standards document.

> The way the text is currently written, it says "it is required for case
> X and not required for case Y" instead of saying "not required for all
> other cases".  If the intended behavior is to not throw an error for
> non-communication routines, then the one example (of datatype
> constructors) should be removed from the standard, or just rewritten as
> "other operations such as datatype constructors".

Exactly.  The sentence "As an argument in datatype constructors,
uncommitted and also committed datatypes
can be used," should be removed completely or otherwise modified such
that there is no potential for it to be misinterpreted as an exclusive
list of permitted usage.

Jeff

-- 
Jeff Hammond
Argonne Leadership Computing Facility
University of Chicago Computation Institute
jhammond at alcf.anl.gov / (630) 252-5381
http://www.linkedin.com/in/jeffhammond
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