Newbie Threads question

[mbf2y at my-dejanews.com]

Hello everyone-

I have never done any threads programming whatsoever.  I did take an Operating
Systems class back in College ('94) so I understand semaphores used to protect
resources, but haven't ever implemented them.

What I'd like to do is learn how to use threads by "parallelizing" a simple
set of now currently serialized tasks.	No shared resources here.  I
understand that in all likelihood I will not get any performance increase
(since I'm on a uni-processor system) but I want to learn how to do this
stuff.

hypothetically my code looks like this:

def func1(param):
   result = []
   # do a bunch of work, takes about 3 seconds of wall-clock time
   return result

def func2(param):
   result = []
   # do a bunch of work, takes about 5 seconds of wall-clock time
   return result

def func3(list1, list2):
   result = []
   # does work on the two lists passed in, takes 0.5 secs of wall-clock time
   return result


#my main loop simplified
list1 = func1(x)
list2 = func2(y)
reallist = func3(list1,list2)
#do something with reallist.

Since func1 and func2 are completely independent - IE do not use any of the
same resources, to me this would be a great place to do the work in parallel.
 What I want to do is something like this:

#my new main loop
list1 = thread.start_new_thread(func1,(x))
list2 = thread.start_new_thread(func2,(y))
reallist = func3(list1,list2)

I have read the documentation a couple of times, but what I don't know:

A) Is the return value of start_new_thread the same as the return value of the
function it calls?

B) Do I need to do anything fancy to make the func3 call wait until the calls
to func1 and func2 have both returned?	For example, should I have the func1
and func2 calls aquire a lock at the start of the function and release it at
the end, and then make the main loop try to acquire both locks before
proceeding to the reallist = func3() call?  If I did this, could the main
loop acquire the locks before the new threads do, causing deadlock?

C) I'm assuming I have to recompile python (since I didn't compile it "with
threads")

Thanks for any help...
-Fred

----
Michael "Fred" Fredericks
Graduate Student, University of Maryland Dept of Computer Science
fred-at-cs-dot-umd-dot-edu
I never read my deja news e-mail

-----------== Posted via Deja News, The Discussion Network ==----------
http://www.dejanews.com/       Search, Read, Discuss, or Start Your Own