How to run two threads parallel?

Question

I start two threads with a button click and each thread invokes a separate routine and each routine will print thread name and value of i.

Program runs perfectly, but I saw Thread1() function running first and then Thread2() routine starts, but I try to run Thread1() and Thread2() both in parallel. Where am I making a mistake?

private void button1_Click(object sender, EventArgs e)
{
    Thread tid1 = new Thread(new ThreadStart(Thread1));
    Thread tid2 = new Thread(new ThreadStart(Thread2));

    tid1.Start();
    tid2.Start();
    MessageBox.Show("Done");
}

public static void Thread1()
{
    for (int i = 1; i <= 10; i++)
    {
    Console.Write(string.Format("Thread1 {0}", i)); 
    }
}

public static void Thread2()
{
    for (int i = 1; i <= 10; i++)
    {
    Console.Write(string.Format("Thread2 {0}", i)); 
    }
}

Answer 1

You can use Parallel.Invoke() method. But it will only work with .Net 4 and above.

  public ParallelDemo()
    {
        Parallel.Invoke(
            () => {
                PrintCount(-10000, 0);
            },
            () => {
                PrintCount(1, 10000);
            }
        );
    }
    public void PrintCount(int LowLimit , int UpperLimit)
    {
        for (int i = LowLimit; i <=UpperLimit; i++)
        {
            Console.WriteLine("> {0}" , i);
        }
    }

Output (Not same for all the systems): Screenshot

Answer 2

this way i achieve my goal. here is the code

using System.Threading.Tasks;
using System.Threading;

    class Program
    {
        static void Main(string[] args)
        {
            Task task1 = Task.Factory.StartNew(() => doStuff("Task1"));
            Task task2 = Task.Factory.StartNew(() => doStuff("Task2"));
            Task task3 = Task.Factory.StartNew(() => doStuff("Task3"));
            Task.WaitAll(task1, task2, task3);

            Console.WriteLine("All threads complete");
            Console.ReadLine();
        }

        static void doStuff(string strName)
        {
            for (int i = 1; i <= 3; i++)
            {
                Console.WriteLine(strName + " " + i.ToString());
                Thread.Yield();
            }
        }
    }

i got a another nice example of Task library from this url https://msdn.microsoft.com/en-us/library/dd460705%28v=vs.110%29.aspx.

here is the code

using System.Threading;
using System.Threading.Tasks;
using System.Net;

class Program
    {
        static void Main()
        {
            // Retrieve Darwin's "Origin of the Species" from Gutenberg.org.
            string[] words = CreateWordArray(@"http://www.gutenberg.org/files/2009/2009.txt");

            #region ParallelTasks
            // Perform three tasks in parallel on the source array
            Parallel.Invoke(() =>
            {
                Console.WriteLine("Begin first task...");
                GetLongestWord(words);
            },  // close first Action

                             () =>
                             {
                                 Console.WriteLine("Begin second task...");
                                 GetMostCommonWords(words);
                             }, //close second Action

                             () =>
                             {
                                 Console.WriteLine("Begin third task...");
                                 GetCountForWord(words, "species");
                             } //close third Action
                         ); //close parallel.invoke

            Console.WriteLine("Returned from Parallel.Invoke");
            #endregion

            Console.WriteLine("Press any key to exit");
            Console.ReadKey();
        }

        #region HelperMethods
        private static void GetCountForWord(string[] words, string term)
        {
            var findWord = from word in words
                           where word.ToUpper().Contains(term.ToUpper())
                           select word;

            Console.WriteLine(@"Task 3 -- The word ""{0}"" occurs {1} times.",
                term, findWord.Count());
        }

        private static void GetMostCommonWords(string[] words)
        {
            var frequencyOrder = from word in words
                                 where word.Length > 6
                                 group word by word into g
                                 orderby g.Count() descending
                                 select g.Key;

            var commonWords = frequencyOrder.Take(10);

            StringBuilder sb = new StringBuilder();
            sb.AppendLine("Task 2 -- The most common words are:");
            foreach (var v in commonWords)
            {
                sb.AppendLine("  " + v);
            }
            Console.WriteLine(sb.ToString());
        }

        private static string GetLongestWord(string[] words)
        {
            var longestWord = (from w in words
                               orderby w.Length descending
                               select w).First();

            Console.WriteLine("Task 1 -- The longest word is {0}", longestWord);
            return longestWord;
        }


        // An http request performed synchronously for simplicity. 
        static string[] CreateWordArray(string uri)
        {
            Console.WriteLine("Retrieving from {0}", uri);

            // Download a web page the easy way. 
            string s = new WebClient().DownloadString(uri);

            // Separate string into an array of words, removing some common punctuation. 
            return s.Split(
                new char[] { ' ', '\u000A', ',', '.', ';', ':', '-', '_', '/' },
                StringSplitOptions.RemoveEmptyEntries);
        }
        #endregion
    }

Answer 3

They are running in parallel. Here is adjusted code to see it better:

    private void test()
    {
        Thread tid1 = new Thread(new ThreadStart(Thread1));
        Thread tid2 = new Thread(new ThreadStart(Thread2));

        tid1.Start();
        tid2.Start();
        Console.Write(string.Format("Done"));

    }
    static void Thread1()
    {
        for (int i = 1; i <= 10; i++)
        {
            Console.Write(string.Format("Thread1 {0}", i));
            Thread.Yield();
        }
    }

    static void Thread2()
    {
        for (int i = 1; i <= 10; i++)
        {
            Console.Write(string.Format("Thread2 {0}", i));
            Thread.Yield();
        }
    }

And here is output: DoneThread1 1Thread2 1Thread1 2Thread2 2Thread1 3Thread2 3Thread1 4Thread2 4Thread1 5Thread2 5Thread1 6Thread2 6Thread1 7Thread2 7Thread1 8Thread2 8Thread1 9Thread2 9Thread1 10Thread2 10

Answer 4

They run parallel, but start with a time delay that is bigger than the runtime of each thread itself. Toss in a delay after each Console.WriteLine and you'll see.

By the way, the more elegant way of starting a new thread is

ThreadPool.QueueUserWorkItem(delegate
{
    //code here
});