(j3.2006) [MPI3 Fortran] Feedback from Fortran J3 meeting

[Van Snyder]

On Wed, 2008-05-28 at 12:06 -0400, Dan Nagle wrote:
> Hello,
> 
> On May 28, 2008, at 11:25 AM, Craig Rasmussen wrote:
> >
> > So Bill suggested earlier using the asynchronous attribute instead.
> > Since MPI_Irecv/MPI_Wait specify asynchronous IO operations,
> > ASYNCHRONOUS seems to me to be the correct syntax.
> 
> But to Fortran, they are simply subroutine calls.
> Further, only one actual argument is "asynchronous",
> and that argument doesn't appear on the mpi wait statement.
> 
> How to identify the asynch argument, identify the start
> of the asynch period, identify the end of the asynch period?
> 
> This seems to me to be a job for argument intents,
> rather than an attribute of a variable.
> 
> >
> > Perhaps this would work if we modified the last line to be
> >
> >       - any statement of the scoping unit is executed while the
> > variable is a pending I/O storage sequence affector or becomes
> > referenced or defined by an external I/O operation
> 
> OK, I'll bite.  What is an "external I/O operation" ?
> How does one start, when has it finished?

In 1997 I proposed that Fortran ought to provide hooks so that I/O
statements ended up in user code instead of the vendor's RTL, precisely
for things like MPI.  We did this type-by-type and list item-by-list
item, instead of connection-by-connection.  If we were to do it
connection-by-connection, is there any reason that ASYNCHRONOUS wouldn't
work?

This is a big enough project that we shouldn't tackle it now.

Keith remarked that many vendors had worked very hard to prevent users
from intercepting I/O.

-- 
Van Snyder                    |  What fraction of Americans believe 
Van.Snyder at jpl.nasa.gov       |  Wrestling is real and NASA is fake?
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