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POMultithreading slower than Singlethreading
 

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  1. POMultithreading slower than Singlethreading
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    <p>I have the following Code (complete content of 'Program.cs' of console application). The single threaded execution of 'countUp' till 'countUp4' takes 13 sec., the multi threaded execution 21 sec.. </p> <p>I have a Intel Core i5-2400 @ 3.10 GHz, 8 GB Ram, Windows 7 64 Bit. So why is the mutli threaded execution slower than the single threaded one?</p> <p>Is multithreading just useful for not blocking the main routine of simple c# applications? When does multithreading give me an advantage in execution speed?</p> <pre><code>using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading; namespace ConsoleApplication1 { class Program { static int counter = 0; static int counter2 = 0; static int counter3 = 0; static int counter4 = 0; static void Main(string[] args) { Console.WriteLine("Without multithreading:"); Console.WriteLine("Start:" + DateTime.Now.ToString()); countUp(); countUp2(); countUp3(); countUp4(); Console.WriteLine(""); Console.WriteLine("With multithreading:"); Console.WriteLine("Start:" + DateTime.Now.ToString()); Thread thread1 = new Thread(new ThreadStart(countUp)); thread1.Start(); Thread thread2 = new Thread(new ThreadStart(countUp2)); thread2.Start(); Thread thread3 = new Thread(new ThreadStart(countUp3)); thread3.Start(); Thread thread4 = new Thread(new ThreadStart(countUp4)); thread4.Start(); Console.Read(); } static void countUp() { for (double i = 0; i &lt; 1000000000; i++) { counter++; } Console.WriteLine(counter.ToString()); Console.WriteLine(DateTime.Now.ToString()); } static void countUp2() { for (double i = 0; i &lt; 1000000000; i++) { counter2++; } Console.WriteLine(counter2.ToString()); Console.WriteLine(DateTime.Now.ToString()); } static void countUp3() { for (double i = 0; i &lt; 1000000000; i++) { counter3++; } Console.WriteLine(counter3.ToString()); Console.WriteLine(DateTime.Now.ToString()); } static void countUp4() { for (double i = 0; i &lt; 1000000000; i++) { counter4++; } Console.WriteLine(counter4.ToString()); Console.WriteLine(DateTime.Now.ToString()); } } } </code></pre>
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    1. USKai Hartmann
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      1. USSimon Edström
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    1. COI am suprised this even works... Are you not accessing the UI thread from the background ones? Is this the actual code?
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      1. USMoonKnight
    2. CONothing of the ordinary here. The Console propably (this is just my guess) needs to be synchronized, thus all threads are waiting on each other. Its a widely common misinformation that multithreading is automatically faster. You have to deal with synchronization, context switches and so on.
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      1. USdowhilefor
    3. COFirst of all, DateTime.Now is a horrible way to time anything, use the `Stopwatch` class instead. Second, not all code benefits from multi-threading.
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      1. USJames Michael Hare
 

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