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odeSolver
Tux's lil' helper
Tux's lil' helper


Joined: 11 Jul 2010
Posts: 84
Location: NJ, USA

PostPosted: Thu Jun 06, 2013 3:37 pm    Post subject: Help with screen's Ctrl-a d Reply with quote

Hello. I (somehow) created a long running MPI program to be run on a Gentoo cluster. I access the cluster using ssh in Cygwin from the fine (*sarcasm*) OS called Windows. My ISP doesn't seem to be able to maintain the consistent connection for the days (maybe weeks) that the program needs to run (besides, I want to watch the new Arrested Development while I wait), so I'm trying to use screen to detach the terminal and let it run in the background. However, when I am in a screen and executing my program, Ctrl-a d doesn't work. Ctrl-a d does work when I am in a screen at the command prompt, but not when executing the program. Any clues as to why I can't get screen's Ctrl-a commands to work when a program is running? (Please speak slowly, I'm a beginner.)

Here is a (slightly edited) version of what my screen looks like when I try (My prompt displays $STY which tells me what screen I'm in):
Code:
()> screen -S testscreen
(testscreen)> mpirun -machinefile $HOME/utils/Host_file -np 4 myprog 6 0
PID 4510 executing on node7.
PID 29130 executing on node8.
PID 2216 executing on node9.
PID 2777 executing on node6.

 Simulating 64x64 oscillators for 9999999 timesteps

 Number of PEs =   4

t = 00000. Overwriting files: /raid/fpuData/N=064x064_Beta=0.00_t=0000000_T.csv,        /raid/fpuData/N=064x064_Beta=0.00_t=0000000_U.csv
^A


See the ^A at the end, that's where I tried to hit Ctrl-a d. But nothing happened.

Also, note that I need to run the program so that I can see all the standard output and error output. I tried running in the background as
Code:
>mpirun -machinefile $HOME/utils/Host_file -np 4 myprog 6 0 >myprog.log 2>&1 &

but the myprog.log was buffered and so when my program slowed (and possibly hung), I could not get all the output. If it's possible to run in the background and ensure the standard output and standard error files are not buffered, I can use that in addition to screen.

Thanks.
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Depserately needs help learning Gentoo Linux in order to use a 32-node cluster for my master's thesis in mathematics.
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bug_report
n00b
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Joined: 17 Sep 2010
Posts: 61
Location: Frankfurt, Germany

PostPosted: Thu Jun 06, 2013 8:00 pm    Post subject: Reply with quote

Do you also have the Ctrl-a problem if you use PuTTY on your Windows computer to connect to the cluster?

Do you have access to the cluster? Do you have the Ctrl-a problem if you start screen and mpirun directly on a console of the cluster?
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odeSolver
Tux's lil' helper
Tux's lil' helper


Joined: 11 Jul 2010
Posts: 84
Location: NJ, USA

PostPosted: Thu Jun 06, 2013 8:13 pm    Post subject: Reply with quote

bug_report wrote:
Do you also have the Ctrl-a problem if you use PuTTY on your Windows computer to connect to the cluster?

Do you have access to the cluster? Do you have the Ctrl-a problem if you start screen and mpirun directly on a console of the cluster?

Yes, I have the same Ctrl-a problem if I use PuTTy. I do not have direct access to the cluster. In fact, my only access is through my PC.
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John R. Graham
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Joined: 08 Mar 2005
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PostPosted: Thu Jun 06, 2013 8:20 pm    Post subject: Reply with quote

You could always log in a second session and issue
Code:
screen -d
which should detach screen in the first session. :wink:

- John
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odeSolver
Tux's lil' helper
Tux's lil' helper


Joined: 11 Jul 2010
Posts: 84
Location: NJ, USA

PostPosted: Thu Jun 06, 2013 9:02 pm    Post subject: Reply with quote

John R. Graham wrote:
You could always log in a second session and issue
Code:
screen -d
which should detach screen in the first session. :wink:

- John

Perfect backup.
I guess maybe a closer reading of the documentation I might have figured that out. How embarrassing.
Thanks.
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