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POPython, using multiprocess is slower than not using it
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  1. POPython, using multiprocess is slower than not using it
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    copied!<p>After spending a lot of time trying to wrap my head around multiprocessing I came up with this code which is a benchmark test:</p> <p><strong>Example 1:</strong></p> <pre><code>from multiprocessing import Process class Alter(Process): def __init__(self, word): Process.__init__(self) self.word = word self.word2 = '' def run(self): # Alter string + test processing speed for i in range(80000): self.word2 = self.word2 + self.word if __name__=='__main__': # Send a string to be altered thread1 = Alter('foo') thread2 = Alter('bar') thread1.start() thread2.start() # wait for both to finish thread1.join() thread2.join() print(thread1.word2) print(thread2.word2) </code></pre> <p>This completes in 2 seconds (half the time of multithreading). Out of curiosity I decided to run this next:</p> <p><strong>Example 2:</strong></p> <pre><code>word2 = 'foo' word3 = 'bar' word = 'foo' for i in range(80000): word2 = word2 + word word = 'bar' for i in range(80000): word3 = word3 + word print(word2) print(word3) </code></pre> <p>To my horror this ran in less than half a second!</p> <p>What is going on here? I expected multiprocessing to run faster - shouldn't it complete in half Example 2's time given that Example 1 is Example 2 split into two processes?</p> <h2>Update:</h2> <p>After considering Chris' feedback, I have included the 'actual' code consuming the most process time, and lead me to consider multiprocessing:</p> <pre><code>self.ListVar = [[13379+ strings],[13379+ strings], [13379+ strings],[13379+ strings]] for b in range(len(self.ListVar)): self.list1 = [] self.temp = [] for n in range(len(self.ListVar[b])): if not self.ListVar[b][n] in self.temp: self.list1.insert(n, self.ListVar[b][n] + '(' + str(self.ListVar[b].count(self.ListVar[b][n])) + ')') self.temp.insert(0, self.ListVar[b][n]) self.ListVar[b] = list(self.list1) </code></pre>
 

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