using System;

public class SingletonBenchmark
{
    const int Iterations = 1000000000;
    
    static DateTime timer;
    
    static void Main()
    {        
        ResetTimer(null);
        
        for (int i=0; i < Iterations; i++)
        {
            SimpleLock sl = SimpleLock.Instance;
        }
        ResetTimer("SimpleLock");
        
        for (int i=0; i < Iterations; i++)
        {
            FixedDcl dcl = FixedDcl.Instance;
        }
        ResetTimer("FixedDcl");

        for (int i=0; i < Iterations; i++)
        {
            BrokenDcl dcl = BrokenDcl.Instance;
        }
        ResetTimer("BrokenDcl");

        for (int i=0; i < Iterations; i++)
        {
            SimpleNoLockLazy inst = SimpleNoLockLazy.Instance;
        }
        ResetTimer("SimpleNoLockLazy");

        for (int i=0; i < Iterations; i++)
        {
            SimpleNoLockNotAsLazy inst = SimpleNoLockNotAsLazy.Instance;
        }
        ResetTimer("SimpleNoLockNotAsLazy");
        
        for (int i=0; i < Iterations; i++)
        {
            NestedLazy nl = NestedLazy.Instance;
        }
        ResetTimer("NestedLazy");

        for (int i=0; i < Iterations; i++)
        {
            NestedNotAsLazy nl = NestedNotAsLazy.Instance;
        }
        ResetTimer("NestedNotAsLazy");
        
    }
    
    static void ResetTimer (string description)
    {
        DateTime now = DateTime.UtcNow;
        if (description != null)
        {
            Console.WriteLine ("{0} took {1}", description, now-timer);
        }
        timer = DateTime.UtcNow;
    }
}

public sealed class SimpleLock
{
    static SimpleLock instance=null;
    static readonly object padlock = new object();

    SimpleLock()
    {
    }

    public static SimpleLock Instance
    {
        get
        {
            lock (padlock)
            {
                if (instance==null)
                {
                    instance = new SimpleLock();
                }
                return instance;
            }
        }
    }
}

public sealed class BrokenDcl
{
    static BrokenDcl instance=null;
    static readonly object padlock = new object();

    BrokenDcl()
    {
    }

    public static BrokenDcl Instance
    {
        get
        {
            if (instance==null)
            {
                lock (padlock)
                {
                    if (instance==null)
                    {
                        instance = new BrokenDcl();
                    }
                }
            }
            return instance;
        }
    }
}

public sealed class FixedDcl
{
    static volatile FixedDcl instance=null;
    static readonly object padlock = new object();

    FixedDcl()
    {
    }

    public static FixedDcl Instance
    {
        get
        {
            if (instance==null)
            {
                lock (padlock)
                {
                    if (instance==null)
                    {
                        instance = new FixedDcl();
                    }
                }
            }
            return instance;
        }
    }
}

public sealed class SimpleNoLockLazy
{
    static readonly SimpleNoLockLazy instance=new SimpleNoLockLazy();

    // Explicit static constructor to tell C# compiler
    // not to mark type as beforefieldinit
    static SimpleNoLockLazy()
    {
    }

    SimpleNoLockLazy()
    {
    }

    public static SimpleNoLockLazy Instance
    {
        get
        {
            return instance;
        }
    }
}

public sealed class SimpleNoLockNotAsLazy
{
    static readonly SimpleNoLockNotAsLazy instance=new SimpleNoLockNotAsLazy();

    SimpleNoLockNotAsLazy()
    {
    }

    public static SimpleNoLockNotAsLazy Instance
    {
        get
        {
            return instance;
        }
    }
}

public sealed class NestedLazy
{
    NestedLazy()
    {
    }

    public static NestedLazy Instance
    {
        get
        {
            return Nested.instance;
        }
    }
    
    class Nested
    {
        // Explicit static constructor to tell C# compiler
        // not to mark type as beforefieldinit
        static Nested()
        {
        }

        internal static readonly NestedLazy instance = new NestedLazy();
    }
}

public sealed class NestedNotAsLazy
{
    NestedNotAsLazy()
    {
    }

    public static NestedNotAsLazy Instance
    {
        get
        {
            return Nested.instance;
        }
    }
    
    class Nested
    {
        internal static readonly NestedNotAsLazy instance = new NestedNotAsLazy();
    }
}