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    <p>In this case, you probably want to define a simple function to perform the calculation and get <code>localResult</code>.</p> <pre><code>def getLocalResult(args): """ Do whatever you want in this func. The point is that it takes x,i,j and returns localResult """ x,i,j = args #unpack args return doSomething(x,i,j) </code></pre> <p>Now in your computation function, you just create a pool of workers and map the local results:</p> <pre><code>import multiprocessing def computation(np=4): """ np is number of processes to fork """ p = multiprocessing.Pool(np) output = p.map(getLocalResults, [(x,i,j) for x in range(i,j)] ) return output </code></pre> <p>I've removed the global here because it's unnecessary (globals are usually unnecessary). In your calling routine you should just do <code>output.extend(computation(np=4))</code> or something similar.</p> <p><strong>EDIT</strong></p> <p>Here's a "working" example of your code:</p> <pre><code>from multiprocessing import Pool def computation(args): length, startPosition, npoints = args print(args) length = 100 np=4 p = Pool(processes=np) p.map(computation, [(startPosition,startPosition+length//np, length//np) for startPosition in range(0, length, length//np)]) </code></pre> <p>Note that what you had didn't work because you were using an instance method as your function. multiprocessing starts new processes and sends the information between processes via <code>pickle</code>, therefore, only objects which can be pickled can be used. Note that it really doesn't make sense to use an instance method anyway. Each process is a copy of the parent, so any changes to state which happen in the processes do not propagate back to the parent anyway. </p>
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    1. POPerform a for-loop in parallel in Python 3.2
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    1. COSorry for not being clear enough, but in the function getLocalResult, I need to know over which interval each process is working. Let's say the total interval is from 0 to 100, that I use 4 processes and that the local interval is given by iLocal and jLocal. Then for the first process, iLocal=0 and jLocal = 25, for the second process iLocal is 26 and jLocal is 50 and so on. Currently, I suppose that x will represent iLocal, but how can I know the end of the interval that the subprocess operates on?
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    2. CO@user1499144 -- Are you doing some sort of domain decomposition? If so, you could replace the list comprehension with something like: `[(i,100//np) for i in range(0,100,100//np)]` -- then sort have a `for` loop inside "getLocalResult".
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    3. COdomain decomposition is exactly what I am trying to do! However, I still don't get it to work after having considered your comments, you can see my entire code in the answer below.
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