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From: Jeff Squyres \(jsquyres\) (jsquyres_at_[hidden])
Date: 2006-06-30 07:24:16


This is due to the way the OMPI finds and loads modules. What actually
happens is that OMPI looks for *all* modules of a given type and
dlopen's them. It then applies the filter of which components are
desired and dlclose's all the undesired ones. It certainly would be
better to apply the filter earlier and only open the desired modules.

We actually identified this behavior quite a while ago, but never put a
high priority on fixing it because we didn't think it would be much of
an issue (because most people build/run in homogeneous environments).
But pending resource availability, I agree that this behavior is
sub-optimal and should be fixed. I'll enter this issue on the bug
tracker so that we don't forget about it. Can you -- and anyone else in
similar circumstances -- let me know how common this scenario is?

There is one workaround, however. The MCA parameter
mca_component_show_load_errors defaults to a "1" value. When it's 1,
all warnings regarding the loading of components are displayed (i.e.,
the messages you're seeing). Setting this value to 0 will disable the
messages. However, you won't see *any* messages about components not
loading. For example, if you have components that you think should be
loading but are not, you won't be notified.

That being said, these messages are not usually a concern for end-users,
however -- they are typically more useful for the OMPI developers. For
example, if a developer accidentally does something to make a plugin
un-loadable (e.g., leaves a symbol out), having these messages displayed
at mpirun time can be *very* useful. Plugins that are shipped in a
tarball hopefully do not suffer from such issues :-), and usually have
rpath information compiled in them so even LD_LIBRARY_PATH issues
shouldn't be much of a problem.

> -----Original Message-----
> From: users-bounces_at_[hidden]
> [mailto:users-bounces_at_[hidden]] On Behalf Of Patrick Jessee
> Sent: Wednesday, June 28, 2006 5:18 PM
> To: Open MPI Users
> Subject: [OMPI users] error messages for btl components that
> aren't loaded
>
>
> Hello. I'm getting some odd error messages in certain situations
> associated with the btl components (happens with both 1.0.2
> and 1.1).
> When certain btl components are NOT loaded, openMPI issues error
> messages associated with those very components. For
> instance, consider
> an application that is built with an openMPI installation that was
> configured with mvapi and mx (in addition to tcp,sm,self). If that
> application is taken to a system that does not have mvapi and mx
> interconnects installed and is explicitly started for TCP by using
> "--mca btl self,tcp,sm", then the following comes from openMPI:
>
> [devi01:01659] mca: base: component_find: unable to open: libvapi.so:
> cannot open shared object file: No such file or directory (ignored)
> [devi01:01659] mca: base: component_find: unable to open: libvapi.so:
> cannot open shared object file: No such file or directory (ignored)
> [devi01:01659] mca: base: component_find: unable to open:
> libmyriexpress.so: cannot open shared object file: No such file or
> directory (ignored)
> [devi02:31845] mca: base: component_find: unable to open: libvapi.so:
> cannot open shared object file: No such file or directory (ignored)
> [devi02:31845] mca: base: component_find: unable to open: libvapi.so:
> cannot open shared object file: No such file or directory (ignored)
> [devi02:31845] mca: base: component_find: unable to open:
> libmyriexpress.so: cannot open shared object file: No such file or
> directory (ignored)
>
> These are not fatal, but they definitely give the wrong
> impression that
> something is not right. The "--mca btl self,tcp,sm" option
> should tell
> openMPI only to load loopback, tcp, and shared memory components (as
> these are the only btl components that should be operational on the
> system). The mvapi and mx components (which need libvapi.so and
> libmyriexpress.so, respectively), should not be loaded and thus
> libvapi.so and libmyriexpress.so should not be needed or even
> searched
> for. The same thing happens with "--mca btl ^mvapi,mx".
> Interestingly,
> even on a system that does have MX, the libmyriexpress.so
> errors show up
> if the mx btl component is not loaded.
>
> Does anyone know (a) why openMPI is complaining about a
> shared library
> from a component that isn't even loaded, and (b) how to avoid the
> seemingly superfluous error messages? Any help is greatly
> appreciated.
>
> -Patrick
>
>
>