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POCode runs extremely slowly inside Google App Engine
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copied!<p>I'm doing some experiments with doing work (in this case, a MD5 brute-forcer) on Google App Engine using the MapReduce framework. </p> <p>I'm having an issue where the code runs extremely slowly inside GAE, even just using the development server</p> <p>This code <a href="https://github.com/jordan-thoms/Hash/blob/f982956f41313cd4fe3b5105aee21ea11bd3af16/src/nz/net/thoms/hash/mapreduce/HashMapper.java" rel="nofollow">https://github.com/jordan-thoms/Hash/blob/f982956f41313cd4fe3b5105aee21ea11bd3af16/src/nz/net/thoms/hash/mapreduce/HashMapper.java</a> will only handle approximately 4,000 hashes per second (this is time inside a single call to map(), and there is no google app engine apis used at all inside it). </p> <p>I took the code outside and ran it standalone - <a href="https://github.com/jordan-thoms/Hash/blob/f982956f41313cd4fe3b5105aee21ea11bd3af16/src/nz/net/thoms/hash/StandaloneTest.java" rel="nofollow">https://github.com/jordan-thoms/Hash/blob/f982956f41313cd4fe3b5105aee21ea11bd3af16/src/nz/net/thoms/hash/StandaloneTest.java</a> , and that version will do over 1 million per second. It's the central loop that's running slower, which is strange since none of that code has anything to do with the google app engine.</p> <p>I've tried running profilers on the Google App engine code, but I haven't found anything useful - seems to be a ton of calls to checkRestricted() and things like that though. I tried removing the security manager </p> <p>Even this simple code:</p> <pre><code> int i; for (i=0; i< 1000000; i++) { i += 2; i += (int) Math.sin(i * (i + (int) System.currentTimeMillis())); } long enda = System.currentTimeMillis(); System.out.println("took " + (enda - starta) + " i:" + i); </code></pre> <p>Runs in 117 ms if I put it in a normal program, and in over 400ms inside a servlet in the developer mode, on the same processor.</p> <p>(Interestingly, the mapper gets about 60,000 hashes done per second on the production Google App Engine. So a lot faster, but still very slow compared to a standalone program)</p>

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