COM/CORBA/DCOP (was: Hello people. I have some questions)

[Paul Rubin]

"Alex Martelli" <aleax at aleax.it> writes:
> > I don't know why people would consider CORBA too heavyweight for
> > connecting desktop apps -- the few performance comparisons between COM
> > and CORBA I have seen show CORBA to be as fast or faster than COM.
> 
> For *in-process* interaction?!  There's something askew here... I
> did the measurements myself back around 1994/1995, under Windows/NT,
> using COM (in-process and out-of-process) and Iona's Orbix, which
> Iona claimed was the fastest ORB for NT, and the difference in
> terms of performance overhead was *at least* an order of magnitude
> in favour of COM (using C to program "toy"-level servers and
> clients, instrumented for measuring communication overhead, and
> striving to simulate the kinds of loads our own applications would
> place on a componentization infrastructure).  Have things changed
> so drastically since then?

As I remember, there are two ways to use COM in-process.  One is to
use the regular dispatch method which does a dictionary lookup.  The
other way is to use a static index to get to the method.  The second
way requires knowing the index, but the method invocation should end
up the same as a C++ method invocation, i.e. just a function call
through a dispatch vector.  I don't see how interacting with a CORBA
ORB can be nearly that fast.  However, the dispatch method might end
up being pretty slow.

Note, my memory of COM is hazy and I've never programmed CORBA.