> Rather than saying that the new datatype is a copy of the old one, I
> would say that it has the same type map. This avoids any notion of
> implementation copies, reference counts etc.
We want to say slightly more than that, I think, since we want *all*
the properties of the new type to be the same as those of the old
one. (The point being that we now have a set of calls which let you
unpick the type, the results of those applied to the new type should
match the results as applied to the old one...)
MPI_COMM_DUP has some nice phrasing like
"creates a new communicator with the same fixed attributes as the
input communicator"
maybe we need phrasing like that here too
"MPI_TYPE_DUP creates a new datatype with same fixed properties as the
input datatype."
The objective is that all the user visible properties of the new type
(apart, of course from its cache) are the same as those of the old
type.
-- Jim
James Cownie
Dolphin Interconnect Solutions
Phone : +44 117 9071438
E-Mail: jcownie@dolphinics.com