Begin forwarded message:
From: Malcolm Cohen <malc...@nag.co.uk>
Date: November 21, 2005 11:23:59 AM MST
To: Aleksandar Donev <ado...@math.princeton.edu>
Cc: J3 <j...@j3-fortran.org>
Subject: (j3.2005) Re: Derived types according to MPI2
Aleksandar Donev said:
Yes, but the interesting thing is neither me nor Van were aware of
what
the standard actually allows in terms of derived types and the
storage
for the components, and presumably we know Fortran better. Can
storage
One might have hoped so.
for the components be separated from the scalar derived type itself?
Hey, when *I* am the Fortran processor there's no contiguous storage,
or for that matter addressable storage! Don't take too limited a view
of current "hard" ware.
how something is done as long as it is done well. But if you want to
pass an array of derived types to a parallel IO routine that is not
compiled by your super-smart Fortran compiler that chooses to scatter
the components across virtual-address space (yes, I mean virtual),
then
you do NOT want that abstraction.
You cannot be serious. You do realise that there is no requirement on
any array even on intrinsic data types to contain the "actual data".
Is that a problem in practice? No of course not.
The Fortran standard doesn't mention virtual addressing, physical
addressing or any of these things. Is that a problem? No.
What the standard should do (and usually does) is to specify the
behaviour
of the Fortran "virtual machine", i.e. the meaning of the program.
How
that program gets mapped to hardware is way outside the scope of the
standard.
It is about choice. Leave preaching to the preachers. Programming
is a
profession for a reason---programmers are experienced and educated
and
understand the issues and don't need lectures on abstractions.
Apparently not.
Cheers,
--
...........................Malcolm Cohen, NAG Ltd., Oxford, U.K.
(malc...@nag.co.uk)
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