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POchrome profiler producing seemingly random results
 

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  1. POchrome profiler producing seemingly random results
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    <p>I am trying to determine which of three ways of calculating something is fastest. To determine this I simply loop a large number of times calling each and expect to look in the profiler to see how long each took.</p> <p>Profiling with both firefox + firebug and IE 9 developer tools gives reasonable results, showing how much time was spent in each function. In Google Chrome though, I never see all three functions in the profile results, and worse, it shows different functions each time, but never all three. I continue to get different looking results each time I run the profiler.</p> <p>I'm assuming the profiler works and I just don't know how to use it, but this sure seems broken to me. I dont see anything to explain this behavior in the <a href="https://developers.google.com/chrome-developer-tools/docs/cpu-profiling" rel="nofollow noreferrer">docs</a>. (I was using normal release but also tried developer release (Version 26.0.1410.10 dev-m) to see if it worked better - it didn't. Increasing the number of times the loop is run, didn't seem to help either)</p> <p>Sample Firebug results (shows the 3 functions + run and onClick as expected): <img src="https://i.stack.imgur.com/c8Jnh.png" alt="enter image description here"></p> <p>Sample Chrome results #1 (shows only 1 of the 3): <img src="https://i.stack.imgur.com/PNRJU.png" alt="Chrome profiler results #1"></p> <p>Sample Chrome results #2 (shows 2 of the 3): <img src="https://i.stack.imgur.com/lQJ7g.png" alt="Chrome profiler results #2"></p> <p>The code being profiled is: </p> <pre><code>&lt;html lang="en" xmlns="http://www.w3.org/1999/xhtml"&gt; &lt;head&gt; &lt;meta charset="utf-8" /&gt; &lt;title&gt;&lt;/title&gt; &lt;/head&gt; &lt;body&gt; &lt;button onclick="run()"&gt;Run Test&lt;/button&gt; &lt;script type="text/javascript"&gt; var R = 6371, toRad = Math.PI / 180; function haversine1(lat1, lon1, lat2, lon2) { var dLat = (lat2 - lat1) * toRad, dLon = (lon2 - lon1) * toRad, a = Math.sin(dLat / 2) * Math.sin(dLat / 2) + Math.cos(lat1 * toRad) * Math.cos(lat2 * toRad) * Math.sin(dLon / 2) * Math.sin(dLon / 2), c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a)); return (R * c); } function haversine2(lat1, lon1, lat2, lon2) { lat1 = lat1 * toRad; lon1 = lon1 * toRad; lat2 = lat2 * toRad; lon2 = lon2 * toRad; var dLat = lat2 - lat1, dLon = lon2 - lon1, a = Math.sin(dLat / 2) * Math.sin(dLat / 2) + Math.cos(lat1) * Math.cos(lat2) * Math.sin(dLon / 2) * Math.sin(dLon / 2), c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a)); return (R * c); } function lawOfCosines(lat1, lon1, lat2, lon2) { lat1 = lat1 * toRad; lon1 = lon1 * toRad; lat2 = lat2 * toRad; lon2 = lon2 * toRad; return Math.acos(Math.sin(lat1) * Math.sin(lat2) + Math.cos(lat1) * Math.cos(lat2) * Math.cos(lon2 - lon1)) * R; } function run() { console.log('Test start'); var lat1 = 90, lat2 = -90, lon1 = 180, lon2 = -180, i = 0, x, y, z while (i++ &lt; 1000000) { lat1 -= .01; lat2 += .01; lon1 -= .01; lon2 += .01; if (lat1 &lt; -90) lat1 = 90; if (lat2 &gt; 90) lat2 = -90; if (lon1 &lt; -180) lon1 = 180; if (lon2 &gt; 180) lon2 = -180; x = haversine1(lat1, lon1, lat2, lon2); y = haversine2(lat1, lon1, lat2, lon2); z = lawOfCosines(lat1, lon1, lat2, lon2); if (i % 1000 === 0) { console.log('x: ' + x + ' y: ' + y + ' z: ' + z); } } console.log('Test end'); } &lt;/script&gt; &lt;/body&gt; &lt;/html&gt; </code></pre>
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    1. COUpdate: When Chrome is restarted, I sometimes get expected results (i.e. I see statistics for all 3 test methods) the first time I profile. (I have a hard time believing what it reports though, as it claims the simpler method the other browsers find marginally fastest to be exponentially slower then the others) Seems to be a Chrome profiler bug. It doesn't seem to work very well for a very simple case...
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