Hi, I most respectively disagree with the "Const simply captures the previously required semantics of the interface in the syntax" statement. The standard did not prohibit a reversible in-place modification of the send buffer until the very recent change related to #45. Adding const on top will automatically make MPI not the greatest common denominator - some internal networking interfaces that were mentioned in this trail will suddenly become "obsolete". That is, most of the existing networking interfaces will. Best regards. Alexander -----Original Message----- From: mpi-22-bounces_at_[hidden] [mailto:mpi-22-bounces_at_[hidden]] On Behalf Of William Gropp Sent: Sunday, March 15, 2009 9:59 PM To: MPI 2.2 Subject: Re: [Mpi-22] Ticket #46: Add const Keyword to the C bindings-implementation Actually, MPI has taken the lead in a number of areas, including cross- language compatibility, to say nothing of the existence of MPI itself. And MPI has taken great pains to be the *greatest* common denominator. Const simply captures the previously required semantics of the interface in the syntax, and is consistent with the MPI spirit. Bill On Mar 13, 2009, at 2:17 PM, Jeff Squyres wrote:

On Mar 13, 2009, at 9:40 AM, William Gropp wrote:

...

First, this is a chicken-and-egg problem; the low level interfaces are unlikely to change to add const unless there is some application that will take advantage of that (and internally, if their semantics allows it and their compiler can support it, they'll just cast to add the const). So MPI should take the lead, particularly since using const also provides information to the user.

This is a very scary statement to me. MPI has not traditionally "taken the lead" on forcing issues with other interfaces (look where it has gotten us with Fortran...). Indeed, MPI has taken great pains to be the lowest common denominator across a variety of language, platforms, and operating systems.

-- Jeff Squyres Cisco Systems

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