You can find the PID of the working process by typing os.getpid() in the worksheet. So to do what you want now, try the following:
os.getpid() and note the PID.factor(2^997-1)) going in the first worksheet. import signal; os.kill(that pid above, signal.SIGSTOP). The first worksheet will appear to be running, but will not use any CPU resources, as you can confirm with top on the server. os.kill(that pid above, signal.SIGCONT). You will see in top that the Python process associated with the first worksheet is back and burning resources. The point of the above exercise is that it illustrates that a pause feature could fully work. To really do this right, one would need to add something to the Sage Notebook itself, e.g., modify the sagenb spkg. This would involve some GUI design choices, etc.
Does the worksheet process do the spawning then (is it the parent)? If so, the PID could be displayed by default for worksheets (since a person might not call os.getpid() first, by forgetting). Or does twisted spawn the processes? Neither? In any case it would be a cool project.
Twisted spawns the worksheet process. It can determine the PID of that process.
There currently isn't any way to pause a computation in the notebook. The only way I can think of the implement such a thing would be to send a SIGTSTP signal to the worker process, but I do not know how the pexpect interface to that process would behave.
Mike -- this is a very good idea. I think it would be likely to work. ccanonc -- as you probably know, on the command line you can just hit "control-Z" to pause, and "fg" to start again.
When I say "likely to work", I mean "with a bunch of work, eventually it could be made to work".
Asked: 2010-08-24 17:01:04 +0100
Seen: 6,081 times
Last updated: Aug 24 '10
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Harder: It would be nice if I could inspect the paused state too.