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POAndroid Fibonacci Benchmark / Deep recursion
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  1. POAndroid Fibonacci Benchmark / Deep recursion
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    copied!<p>I'm running a Fibonacci benchmark on my Android phone and I'm getting some strange results. As I don't really care if the UI-thread is locked or not, I'm running the code below inside the UI-thread in my application (could this affect the performance btw?).</p> <pre><code>public void startBenchmark(View view) { results = ""; results += String.format("Begin test"); for (int i = 45; i &lt; 46; i++) { startTime = System.currentTimeMillis(); fib(i); results += String.format("%d\n", System.currentTimeMillis() - startTime); } results += String.format("End test"); Log.d("Results", results); Log.d("Status", "Finished"); } private static int fib(int n) { return n &lt;= 1 ? n : fib(n - 1) + fib(n - 2); } </code></pre> <p>I've also implemented the corresponding code in JavaScript; </p> <pre><code>function performBenchmark() { for (var i = 45; i &lt; 46; i++) { benchmark(i) } } function benchmark(n){ var start= Date.now(); document.getElementById("disp").innerHTML += "fib(" + n + "): " + fib(n) + " &lt;br /&gt;"; document.getElementById("results").innerHTML += (Date.now() - start) + "&lt;br /&gt;"; } function fib(n) { return n &lt;= 1 ? n : fib(n - 1) + fib(n - 2); } </code></pre> <p>My problem is that for fib(45) I get something like 420 seconds on the native platform using Java and 120 seconds using Javascript in Chrome, both running on my Samsung Galaxy Nexus. </p> <p>Is there something blatantly wrong with my implementation in Java for Android that could be slowing down the benchmark?</p> <p>NOTE; <strong>I'm not primarily looking to switch to a faster algorithm but I'm trying to understand why Javascript (and also an implementation I made for iOS) is much faster than the implementation in Java for Android.</strong> </p> <p>Running on my laptop I get much faster results for Java than for Javascript.</p>
 

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