Just to strengthen what Brian said...
We agree that what you cite is a problem. The only issue is that we
don't know of any way to do it better -- Brian laid out the 3 possible
options below pretty well. --enable-mca-static might be a decent
solution for you; you still build libmpi.so (not libmpi.a), but all
the plugins are slurped up into libmpi instead of being dlopened at
run-time.
It's really a larger issue than just Open MPI -- private namespaces
are, in general, a Good Thing, but they are problematic for *any*
plugin-based system that gets opened in a private namespace. What
would be a Real solution would be somehow having a way that Open MPI
could dlopen its plugins *within* its private namespace. That's
unfortunately beyond our control to influence.
On Mar 25, 2009, at 9:10 AM, Brian W. Barrett wrote:
On Mon, 23 Mar 2009, Olaf Lenz wrote:
> and the solution that is described there still looks as though it
should
> still work now, or shouldn't it? Just link all the OpenMPI plugins
against
> the base OpenMPI libraries, and it should work. Or am I wrong?
I believe your suggestion will not work, certainly not portably. In
fact,
it will die in horrible ways. We used to link in the way you
suggested,
and what you end up with is a bunch of copies of libmpi, all in
their own
namespace. Hardly helpful :).
Unfortunately, there are only three rational solutions I've thought
of to
the problem:
* Do nothing, my prefered solution
* Stop building components by default
* Have libmpi be a thin wrapper, which dlopens Open MPI's guts into
the
public namespace, and the guts then dlopen all the components.
Obviously, the first serves the greatest community and involves the
least
amount of work. However, packagers such as the Linux distributions
should
make a decision about how to best package Open MPI -- perhaps shipping
it built with components is not the ideal solution for their
infrastructure.
I did want to point out one incorrect statement in your e-mail. While
specifying "--enable-shared --enable-static" to configure will cause
components to be linked into libmpi rather than built as stand-alone
entities, a better way to accomplish that is "--enable-mca-static",
which
will build all the components into libmpi.so, but not also cause
libmpi.a
to be built.
Brian
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Jeff Squyres
Cisco Systems
