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POAre lambda functions faster than delegates/anonymous functions?
 

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  1. POAre lambda functions faster than delegates/anonymous functions?
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    <p>I assumed <code>lambda functions</code>, <code>delegates</code> and <code>anonymous functions</code> with the same body would have the same "speed", however, running the following simple program:</p> <pre><code>static void Main(string[] args) { List&lt;int&gt; items = new List&lt;int&gt;(); Random random = new Random(); for (int i = 0; i &lt; 10000000; i++) { items.Add(random.Next()); } Stopwatch watch; IEnumerable&lt;int&gt; result; Func&lt;int, bool&gt; @delegate = delegate(int i) { return i &lt; 500; }; watch = Stopwatch.StartNew(); result = items.Where(@delegate); watch.Stop(); Console.WriteLine("Delegate: {0}", watch.Elapsed.TotalMilliseconds); Func&lt;int, bool&gt; lambda = i =&gt; i &lt; 500; watch = Stopwatch.StartNew(); result = items.Where(lambda); watch.Stop(); Console.WriteLine("Lambda: {0}", watch.Elapsed.TotalMilliseconds); watch = Stopwatch.StartNew(); result = items.Where(i =&gt; i &lt; 500); watch.Stop(); Console.WriteLine("Inline: {0}", watch.Elapsed.TotalMilliseconds); Console.ReadLine(); } </code></pre> <p>I get:</p> <blockquote> <p>Delegate: 4.2948 ms</p> <p>Lambda: 0.0019 ms</p> <p>Anonymous: 0.0034 ms</p> </blockquote> <p>Although negligible, why are these three - apparently identical - methods running at different speeds? What's happening under the hood?</p> <hr> <p><strong>Update:</strong></p> <p>As suggested by the comments, the following "forces" the <code>Where</code> by calling <code>ToList()</code> on it. In addition, a loop is added to offer more run data:</p> <pre><code>while (true) { List&lt;int&gt; items = new List&lt;int&gt;(); Random random = new Random(); for (int i = 0; i &lt; 10000000; i++) { items.Add(random.Next()); } Stopwatch watch; IEnumerable&lt;int&gt; result; Func&lt;int, bool&gt; @delegate = delegate(int i) { return i &lt; 500; }; watch = Stopwatch.StartNew(); result = items.Where(@delegate).ToList(); watch.Stop(); Console.WriteLine("Delegate: {0}", watch.Elapsed.TotalMilliseconds); Func&lt;int, bool&gt; lambda = i =&gt; i &lt; 500; watch = Stopwatch.StartNew(); result = items.Where(lambda).ToList(); watch.Stop(); Console.WriteLine("Lambda: {0}", watch.Elapsed.TotalMilliseconds); watch = Stopwatch.StartNew(); result = items.Where(i =&gt; i &lt; 500).ToList(); watch.Stop(); Console.WriteLine("Inline: {0}", watch.Elapsed.TotalMilliseconds); Console.WriteLine(new string('-', 12)); } </code></pre> <p>The above code results in ~120 ms for each function.</p>
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    1. COjust out of curiosity, did you try running the 3 in different orders?
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      1. USkenwarner
    2. COThe second and third are both lambdas.
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      1. USIgby Largeman
    3. COAdd warmup period and run all tests several cycles (big loop around all) and force Where. After these changes I see no perceptible difference.
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