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Subject: Re: [OMPI users] glut display 'occasionally' opens
From: brad baker (bl.baker.85_at_[hidden])
Date: 2010-12-07 14:12:17


Thanks for your responses! I'm at home today so I can't actually do any
tests to 'see' if anything works. But I logged in remotely and I did as
Ralph suggested and ran env as my app. No process returned a value for
DISPLAY. Then I made a small program that calls getenv("DISPLAY") to run
with mpi, and each process returns NULL.

I did some googling and found in the mpirun man
page<http://linux.die.net/man/1/mpirun>
:

"*Exported Environment Variables*
The *-x* option to *mpirun* can be used to export specific environment
variables to the new processes. While the syntax of the *-x* option allows
the definition of new variables, note that the* parser for this option is
currently not very sophisticated* - it does not even understand quoted
values. Users are advised to* set variables in the environment and use **-x*
* to export them; not to define them*."
So it looks like I need to manually set them, possible how Jeff suggested.
 I'll do some more research on this and get back after I've tried a few
things in the lab.

Thanks again!
Brad

On Tue, Dec 7, 2010 at 10:26 AM, Jeff Squyres <jsquyres_at_[hidden]> wrote:

> Are you using ssh to launch OMPI between your nodes? (i.e., is mpirun
> using ssh under the covers to launch on remote nodes)
>
> If so, you might want to just set OMPI to use "ssh -X", which sets up SSH
> tunneled X forwarding, and therefore it sets DISPLAY for you properly on all
> the remote nodes automatically. But it does have the disadvantage of being
> a bit slow, since it's coming through ssh.
>
> Alternatively, you can xhost +<source_host>, where <source_host> is the
> host where your X app is running. Then set your DISPLAY variable manually
> to <source_host>:display and it'll just go in an unencrypted fashion. This
> is normal X forwarding stuff -- you can probably google around for more info
> on this.
>
> NOTE: IIRC, xauth is better than xhost these days. I stopped using X for
> most things many years ago, so my xhost/xauth information is probably a
> little dated. Google around for the most recent / best ways to do this
> stuff.
>
>
> On Dec 6, 2010, at 10:11 PM, Ralph Castain wrote:
>
> > BTW: you might check to see if the DISPLAY envar is being correctly set
> on all procs. Two ways to do it:
> >
> > 1. launch "env" as your app to print out the envars - can be messy on the
> output end, though you could use the mpirun options to tag and/or split the
> output from the procs
> >
> > 2. in your app, just do a getenv and print the display envar
> >
> > Would help tell us if there is an OMPI problem, or just a problem in how
> you setup X11
> >
> >
> > On Dec 6, 2010, at 9:18 PM, Ralph Castain wrote:
> >
> >> Hmmm...yes, the code does seem to handle that '=' being in there. Forgot
> it was there.
> >>
> >> Depending on the version you are using, mpirun could just open the
> display for you. There is an mpirun option that tells us to please start
> each app in its own xterm.
> >>
> >> You shouldn't need forwarding if you are going to see it on a local
> display (i.e., one physically attached to the node), assuming you are logged
> into those nodes (otherwise you don't own the display).
> >>
> >> If you are trying to view it on your own local display, then you do need
> forwarding setup.
> >>
> >>
> >> On Dec 6, 2010, at 8:36 PM, brad baker wrote:
> >>
> >>> Without including the -x DISPLAY, glut doesn't know what display to
> open. For instance, without the -x DISPLAY parameter glut returns an error
> from each process stating that it could not find display "" (empty string).
> This strategy is briefly described in the openmpi FAQs for launching gui
> applications with openmpi.
> >>>
> >>> I'm assuming that by setting the DISPLAY envar to :0.0, each process
> will render to their local display, which is my intention, and as I
> previously stated works for up to 2 processes. So I believe it to be
> necessary.
> >>>
> >>> But I'm thinking I may have to configure some kind of X11 forwarding.
> I'm not sure...
> >>>
> >>> Thanks for your reply! Any more ideas?
> >>> Brad
> >>>
> >>>
> >>> On Mon, Dec 6, 2010 at 6:31 PM, Ralph Castain <rhc_at_[hidden]>
> wrote:
> >>> Guess I'm not entirely sure I understand how this is supposed to work.
> All the -x does is tell us to pickup an envar of the given name and forward
> its value to the remote apps. You can't set the envar's value on the cmd
> line. So you told mpirun to pickup the value of an envar called
> "DISPLAY=:0.0".
> >>>
> >>> So yes - I would expect this would be behaving strangely.
> >>>
> >>> If you tell us -x DISPLAY, we'll pickup the local value of DISPLAY and
> forward it. What that will cause your app to do is, I suppose, up to it.
> >>>
> >>>
> >>> On Dec 6, 2010, at 12:42 PM, brad baker wrote:
> >>>
> >>> > Hello,
> >>> >
> >>> > I'm working on an mpi application that opens a glut display on each
> node of a small cluster for opengl rendering (each node has its own
> display). My current implementation scales great with mpich2, but I'd like
> to use openmpi infiniband, which is giving me trouble.
> >>> >
> >>> > I've had some success with the -x DISPLAY=:0.0 parameter to mpirun,
> which will open the display on up to 2 of my nodes... any 2. But when I
> attempt to run the application on 4 nodes, the display is non-deterministic.
> If any open at all process 0 definately will, and sometimes process 3 along
> with that. I haven't observed much behavior from process 1 or 2.
> >>> >
> >>> > My command:
> >>> >
> >>> > mpirun -x DISPLAY=:0.0 -np 4 -hostfile ~/openmpi.hosts ./myapp
> >>> >
> >>> > I've tried adding the -d option with no success.
> >>> >
> >>> > Does anyone have any suggestions or comments? I'll certainly provide
> more information if required.
> >>> >
> >>> > Thanks,
> >>> > Brad
> >>> > _______________________________________________
> >>> > users mailing list
> >>> > users_at_[hidden]
> >>> > http://www.open-mpi.org/mailman/listinfo.cgi/users
> >>>
> >>>
> >>> _______________________________________________
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> >>>
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> >>
> >
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>
> --
> Jeff Squyres
> jsquyres_at_[hidden]
> For corporate legal information go to:
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