Two comments: 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. Second, MPI also runs on systems with tighter integration with the interconnect; not all implementations are on top of other middleware layers, so the failure of those layers to make use of const (and restrict) isn't a good argument for MPI to wait on them. Finally, MPICH2 has used const (and even restrict!) internally in places where a sophisticated compiler can take advantage of it. So its not just syntactic sugar. Bill On Mar 12, 2009, at 2:04 PM, Underwood, Keith D wrote:

It would seem like const would eventually have to be cast away for most lower level interfaces. Portals, Elan, IB Verbs, and as best I can tell MX don't have const on their send buffers...

Keith

William Gropp Deputy Director for Research Institute for Advanced Computing Applications and Technologies Paul and Cynthia Saylor Professor of Computer Science University of Illinois Urbana-Champaign