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POSimple math operations faster on double than on float datatype?
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copied!<blockquote> <p><strong>Possible Duplicate:</strong><br> <a href="https://stackoverflow.com/questions/158889/are-doubles-faster-than-floats-in-c">Are doubles faster than floats in c#?</a> </p> </blockquote> <p>I wrote simple benchmark to check how much performance i can get changing <code>double</code> datatype to <code>float</code> in my application. Here is my code:</p> <pre><code> // my form: // one textbox: textbox1 (MultiLine property set to true) // one button: button1 with event button1_Click private void button1_Click(object sender, EventArgs e) { int num = 10000000; float[] floats1 = new float[num]; float[] floats2 = new float[num]; float[] floatsr = new float[num]; // array for results double[] doubles1 = new double[num]; double[] doubles2 = new double[num]; double[] doublesr = new double[num]; // array for results Stopwatch stw = new Stopwatch(); log("Preparing data"); Random rnd = new Random(); stw.Start(); for (int i = 0; i < num; i++) { floats1[i] = NextFloat(rnd); floats2[i] = NextFloat(rnd); doubles1[i] = rnd.NextDouble(); doubles2[i] = rnd.NextDouble(); } stw.Stop(); log(stw.Elapsed.TotalMilliseconds.ToString()+"ms"); stw.Reset(); log(""); stw.Start(); for (int i = 0; i <# i++) { floatsr[i] = floats1[i] * floats2[i]; } stw.Stop(); log("Multiplying floats: " + stw.Elapsed.TotalMilliseconds.ToString() + "ms"); stw.Reset(); stw.Start(); for (int i = 0; i < num; i++) { doublesr[i] = doubles1[i] * doubles2[i]; } stw.Stop(); log("Multiplying doubles: " + stw.Elapsed.TotalMilliseconds.ToString() + "ms"); stw.Reset(); stw.Start(); for (int i = 0; i < num; i++) { floatsr[i] = floats1[i] / floats2[i]; } stw.Stop(); log("Dividing floats: " + stw.Elapsed.TotalMilliseconds.ToString() + "ms"); stw.Reset(); stw.Start(); for (int i = 0; i < num; i++) { doublesr[i] = doubles1[i] / doubles2[i]; } stw.Stop(); log("Dividing doubles: " + stw.Elapsed.TotalMilliseconds.ToString() + "ms"); stw.Reset(); } private void log(string text) { textBox1.Text = textBox1.Text + text + Environment.NewLine; } // I found that function somewhere on stackoverflow static float NextFloat(Random random) { double mantissa = (random.NextDouble() * 2.0) - 1.0; double exponent = Math.Pow(2.0, random.Next(-126, 128)); return (float)(mantissa * exponent); } </code></pre> <p>I got results like this (release, no debug, Intel Mobile Core Duo T2500 2.0GHz 2MB CPU):</p> <pre><code>Preparing data 5275,6862ms Multiplying floats: 442,7865ms Multiplying doubles: 169,4028ms Dividing floats: 550,7052ms Dividing doubles: 164,1607ms </code></pre> <p>I was suprised, that operations on <code>double</code> are almost 3 times faster than operations on <code>float</code>. I searched for "double float" here, and i found this:</p> <p><a href="https://stackoverflow.com/questions/3426165/is-using-double-faster-than-float">Is using double faster than float?</a></p> <p>Best answer is focused on CPU architecture, but I cant agree with that.</p> <p>I suspect that something else is causing low performance on floats, because my CPU with Intel SSE should be able to multiply or divide 4 floats at once (packed floating point instructions), or 2 doubles at once. So floats should be faster.</p> <p>Maybe compiler (or clr in .net) is optimizing memory usage somehow?</p> <p><strong>Is there any way to optimize it and make float faster?</strong></p> <p><strong>Please don't report duplicate, i saw other questions and they not satisfying me.</strong></p> <hr> <p>My results after changing method for generating floats now look fine (suggested by Servy): </p> <pre><code>Preparing data 1367,0678ms Multiplying floats: 109,8742ms Multiplying doubles: 149,9555ms Dividing floats: 167,0079ms Dividing doubles: 168,6821ms </code></pre>

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