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Subject: Re: [OMPI users] Tracing the library using gdb and xterm
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2008-01-02 10:28:07


Another simpler (but not secure) option would be do run "xhost
+hostname" for each machine that you'll be using and then use un-
encrypted X connections to pipe back to your display. This avoids a
bunch of issues (e.g., the ssh to launch the MPI job quitting because
it successfully launched on the remote node) and is generally simpler.

On a closed LAN/cluster, it may be ok to do this... but your security
administrators may disagree with me. :-) I suggest that you check
with your admins.

Specifically, try something like this:

     shell$ for host in `cat machines`; do xhost +$host: $host; done

This tells the X server to accept connections from all the hosts in
your machines file. Then you can mpirun with something like this:

     shell$ mpirun --prefix /usr/local -hostfile machines \
         -x DISPLAY=yourhost:0.0 -np 2 xterm -e gdb peruse_ex1

mpirun's -x option exports the environment variable listed, and the
"=foo" argument tells it to assign that value on the remote nodes.
Hence, the DISPLAY environment variable will be loaded with the value
"yourhost:0.0" on the remote nodes. Obviously, you need to replace
"yourhost:0.0" with the hostname and display number of the host that
you're launching from.

Hope that helps.

On Jan 1, 2008, at 1:40 PM, Doug Reeder wrote:

> Krishna,
>
> If you are using ssh to connect to the second machine you need to be
> sure that ssh X11 forwarding is enabled and you may need to have mpi
> use ssh -X or ssh -Y to connect to the second machine. That is how
> the DISPLAY gets set using ssh.
>
> Doug Reeder
>
> On Jan 1, 2008, at 8:11 AM, Krishna Chaitanya wrote:
>
>> Hi,
>> I have been tracing the interactions between the
>> PERUSE and MPI library,on one machine. I have been using gdb along
>> with xterm to have two windows open at the same time as I step
>> through the code. I wish to get a better glimpse of the working of
>> the point to point calls, by launching the job on two machines and
>> by tracing the flow in a similar manner. This is where I stand as
>> of now :
>>
>> mpirun --prefix /usr/local -hostfile machines -np 2 xterm -e gdb
>> peruse_ex1
>> xterm Xt error: Can't open display:
>> xterm: DISPLAY is not set
>>
>> I tried using the display option for xterm and
>> setting the value as 0.0, that was not of much help.
>> If someone can guide me as to where the DISPLAY
>> parameter has to be set to allow the remote machine to open the
>> xterm window, it will be of great help.
>>
>> Thanks,
>> Krishna
>>
>>
>>
>> --
>> In the middle of difficulty, lies opportunity
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>> users mailing list
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>
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-- 
Jeff Squyres
Cisco Systems