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belson17

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"sresult" referenced before assignment in pp.py

« on: March 22, 2010, 08:20:16 AM »

Hello,
I don't know if this is a problem with my usage of PP or not, but I'm consistently getting errors like this:

Code:

Traceback (most recent call last):
File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/pp.py", line 762, in __run
sresult = worker.t.receive()
File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/pptransport.py", line 132, in receive
msg_len = struct.unpack("!Q", size_packed)[0]
struct.error: unpack requires a string argument of length 8
Unhandled exception in thread started by <bound method Server.__run of <pp.Server object at 0x13b3570>>
Traceback (most recent call last):
File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/pp.py", line 771, in __run
job.finalize(sresult)
UnboundLocalError: local variable 'sresult' referenced before assignment

I'm running on a Mac Pro with OS 10.6 and 8 cores total. Only some of the parallel jobs quit with this error, others keep going. Has anyone else seen this, or at least know if this is a result of my usage or a problem with PP? Is it unique to Mac OS?

Thanks!


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ppdnam

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Re: "sresult" referenced before assignment in pp.py

« Reply #1 on: March 24, 2010, 10:51:01 AM »

Hey,

You're not alone, and this is not unique to MacOS - I've had this problem with PP as well, though I've found it hard to reproduce. I did have some issues with PP & scipy weave - turns out that any C-code you weave.inline that writes to stdout causes either a pipe error or sresult. I've seen it in some other code I've written as well.

As I say, it's not easy to reproduce (for me), often re-running the script with a smaller subset of the data does not generate the error. Perhaps you could post a code snippet that throws the exception consistently?


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cswiggett

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Re: "sresult" referenced before assignment in pp.py

« Reply #2 on: March 24, 2010, 03:50:17 PM »

I can get this error to happen reliably if I kill off one of my worker threads.

Here's how I launch them:

Code:

# Setup the job server
jobServer = pp.Server(ncpus=60, ppservers="*", loglevel=10)

...
# run a script
jobServer.submit(LaunchPythonScript, (id), modules=('scripts.%s'%parsescriptId, 'sflog',))

Here's what gets launched:

Code:

def LaunchPythonScript(parsescriptId):
modulename = ''.join(["scripts.", id])
scriptmodule = None
if modulename in sys.modules:
scriptmodule = sys.modules[modulename]
reload(scriptmodule)
else:
parentmodule = __import__(modulename, globals(), locals(), [], -1)
scriptmodule = parentmodule.__dict__[parsescriptId]
scriptclass = scriptmodule.__dict__[''.join([parsescriptId, 'Script'])]
scriptinstance = scriptclass.__new__(scriptclass, parsescriptId, instanceId)
if isinstance(scriptinstance, scriptclass):
scriptclass.__init__(scriptinstance, parsescriptId, instanceId)
scriptinstance._runScript(context)
return True

If I kill one of the active python.exe processes, then it generates the following error:

Code:

File "C:\Python26\lib\site-packages\pp.py", line 762, in __run
sresult = worker.t.receive()
File "C:\Python26\lib\site-packages\pptransport.py", line 132, in receive
msg_len = struct.unpack("!Q", size_packed)[0]
struct.error: unpack requires a string argument of length 8
Unhandled exception in thread started by <bound method Server.__run of <pp.Server object at 0x015D0BF0>>
Traceback (most recent call last):
File "C:\Python26\lib\site-packages\pp.py", line 771, in __run
job.finalize(sresult)
UnboundLocalError: local variable 'sresult' referenced before assignment
CRITICAL 2010-03-24 15:19:44,039(local) host:clif pid:3328 sfmgr.py(270) TEST002 0 StillAlive not received within 60.000000 seconds
2010-03-24 15:19:45,743 DEBUG Task 1 submited, function='LaunchPythonScript'
2010-03-24 15:19:45,743 DEBUG Task 1 started
Traceback (most recent call last):
File "C:\Python26\lib\site-packages\pp.py", line 760, in __run
worker.t.csend(sfunc)
File "C:\Python26\lib\site-packages\pptransport.py", line 96, in csend
self.send("H" + hash1)
File "C:\Python26\lib\site-packages\pptransport.py", line 125, in send
self.w.write(struct.pack("!Q", len(msg)))
IOError: [Errno 22] Invalid argument
Unhandled exception in thread started by <bound method Server.__run of <pp.Server object at 0x015D0BF0>>
Traceback (most recent call last):
File "C:\Python26\lib\site-packages\pp.py", line 771, in __run
job.finalize(sresult)
UnboundLocalError: local variable 'sresult' referenced before assignment

I haven't tried to debug this yet. But maybe this'll help shed light on what the problem might be..


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belson17

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Posts: 4

Re: "sresult" referenced before assignment in pp.py

« Reply #3 on: March 26, 2010, 11:12:45 AM »

I'm still not sure what is causing this, but I have found other potential problems with my code, so for now I can't really pinpoint the problem. If it keeps coming up after I fix the other things, I'll try to isolate it better.


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krb

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Posts: 23

Re: "sresult" referenced before assignment in pp.py

« Reply #4 on: April 29, 2010, 04:20:08 AM »

Hi,

I have seen this issue on a windows vista running python 2.6.1 and pp 1.5.7.
I have seen this when calling the destroy() method on a ppserver.

Krb


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Vitalii

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Posts: 516

Re: "sresult" referenced before assignment in pp.py

« Reply #5 on: May 29, 2010, 11:19:29 PM »

Could you please try your code with PP 1.6?
http://www.parallelpython.com/component/option,com_smf/Itemid,29/topic,440.0
It had lots of various fixes so this issue might have been fixes as well.


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cswiggett

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Re: "sresult" referenced before assignment in pp.py

« Reply #6 on: April 15, 2011, 03:34:04 PM »

I have seen this issue in another situation and have what may be a fix. Vitalii, does this look like a valid solution.

Python 2.6, PP 1.6.1, windows XP

The problem: Create a server, submit a couple jobs, then call server.destroy() while the jobs are still running. In pp 1.5.7, server.destroy() successfully kills off all worker processes whether or not they were executing jobs. In 1.6.1, active worker threads are not killed off and the next time I create a server it is unable to execute new jobs.

The problem appears to be in Server.destroy():

Code:

for worker in self.__workers:
try:
worker.t.close()
if sys.platform.startswith("win"):
os.popen('TASKKILL /PID '+str(worker.pid)+' /F')
else:
os.kill(worker.pid, 9)
os.waitpid(worker.pid, 0)
except:
pass

For worker processes that still have jobs running, worker.t.close() throws an exception 'IOError: close() called during concurrent operation on the same file object.' So I modified the code as follows.

Code:

for worker in self.__workers:
try:
if sys.platform.startswith("win"):
os.popen('TASKKILL /PID '+str(worker.pid)+' /F')
else:
os.kill(worker.pid, 9)
os.waitpid(worker.pid, 0)
worker.t.close()

No more exceptions and no more worker processes hanging around. I haven't seen any negative side effects.


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Vitalii

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Posts: 516

Re: "sresult" referenced before assignment in pp.py

« Reply #7 on: May 06, 2011, 01:25:19 AM »

Thanks for the suggestion.
To make sure an exception in closing or killing won't stop the other one from executing:

Code: (python)

            
          try:
                worker.t.close()
            except:
                pass
           try:
                if sys.platform.startswith("win"):
                    os.popen('TASKKILL /PID '+str(worker.pid)+' /F')
                else:
                    os.kill(worker.pid, 9)
                    os.waitpid(worker.pid, 0)
            except:
                pass

I will include it in the next version of PP.


« Last Edit: May 06, 2011, 01:27:10 AM by Vitalii »	Logged

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