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PO
 

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    <p>I don't think that's inconceivable at all. You have an application where the "payload" is fairly minuscule (though that of course depends on the value of <code>n</code>), and you have to accept that the extra effort required (to connect the profiler and shift all the information across to it) will swamp that payload.</p> <p>This is not the sort of application I would be profiling in the first place since it's pretty obvious that the vast amount of time would be spent in <code>fib</code> anyway (for non-trivial values of <code>n</code>), marking that as an obvious target for optimisation.</p> <p>I would be more inclined to use the profiler for more substantial applications where:</p> <ul> <li>it's not obvious where the optimisation effort should go; and</li> <li>there is some substantial amount of work to do in the payload.</li> </ul> <p>If you really want to test <em>that</em> code, you probably need to bump up its effect by (for example) replacing:</p> <pre><code>int fib = fib(n); </code></pre> <p>with:</p> <pre><code>for (int i = 0; i &lt; 100000; i++) { int fib = fib(n); ) </code></pre> <hr> <p>I'll tell you <em>one</em> thing to watch out for though. I don't know the internals of any particular JVM but using a recursive method where the reduction of the argument is slow is usually a bad idea, one that leads to stack space being exhausted pretty quickly.</p> <p>By that, I mean a binary search is a good candidate since it removes half the remaining search space with each recursion level (so that a search space of a billion items is only 30 levels).</p> <p>On the other hand, using recursion for a Fibonacci sequence on the number 1,000,000,000 would take about a billion levels and most stacks would have a hard time containing that.</p> <p>Tail end recursion optimisation may avoid that problem but you need to be careful in case that optimisation isn't done.</p>
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    1. POJava VisualVM giving bizarre results for CPU profiling - Has anyone else run into this?
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    1. COThanks for your thoughtful answer. I am not really interested in profiling a recursive fibonacci finder. I was trying to profile a real piece of software with VisualVM and was getting the same confusing results.
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      1. USFrancis Stephens
 

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