From 3d503852ad1c51094b02af8ddb351edf2a4077b9 Mon Sep 17 00:00:00 2001
From: "gu.martinm@gmail.com" <gu.martinm@gmail.com>
Date: Fri, 23 May 2014 04:04:48 +0200
Subject: [PATCH] Threads and C#

http://parallelpatterns.codeplex.com/

Chapter 6: Dynamic Task Parallelism
---
 Allgemeines/Threads/Threads/Chapter6.cs    | 70 ++++++++++++++++++++++++++++++
 Allgemeines/Threads/Threads/Program.cs     | 12 +++++
 Allgemeines/Threads/Threads/Threads.csproj |  1 +
 3 files changed, 83 insertions(+)
 create mode 100644 Allgemeines/Threads/Threads/Chapter6.cs

diff --git a/Allgemeines/Threads/Threads/Chapter6.cs b/Allgemeines/Threads/Threads/Chapter6.cs
new file mode 100644
index 0000000..79ed287
--- /dev/null
+++ b/Allgemeines/Threads/Threads/Chapter6.cs
@@ -0,0 +1,70 @@
+using System;
+using System.Threading.Tasks;
+using System.Runtime.InteropServices;
+
+namespace Threads
+{
+    public class Chapter6
+    {
+        /// <summary>
+        /// 
+        /// Chapter 6.
+        /// Dynamic Task Parallelism
+        /// 
+        /// Taken from http://msdn.microsoft.com/en-us/library/ff963551.aspx
+        /// 
+        /// </summary>
+
+        public void FillTree<T>(int level, Tree<T> node, Func<T> function)
+        {
+            node.Data = function();
+            node.Level = level;
+
+            level = level - 1;
+            if (level == 0)
+            {
+                return;
+            }
+
+            node.Left = new Tree<T>();
+            FillTree(level, node.Left, function);
+            node.Right = new Tree<T>();
+            FillTree(level, node.Right, function);
+        }
+
+        public void SequentialWalk<T>(Tree<T> tree, Action<T, int> action)
+        {
+            if (tree == null)
+            {
+                return;
+            }
+
+            action(tree.Data, tree.Level);
+            this.SequentialWalk(tree.Left, action);
+            this.SequentialWalk(tree.Right, action);
+        }
+
+        public void ParallelWalk<T>(Tree<T> tree, Action<T, int> action)
+        {
+            if (tree == null)
+            {
+                return;
+            }
+
+            var t1 = Task.Factory.StartNew(() => action(tree.Data, tree.Level));
+            var t2 = Task.Factory.StartNew(() => ParallelWalk(tree.Left, action));
+            var t3 = Task.Factory.StartNew(() => ParallelWalk(tree.Right, action)); 
+
+            Task.WaitAll(t1, t2, t3);
+        }
+
+        public class Tree<T>
+        {
+            public T       Data  { get; set; }
+            public int     Level { get; set; }
+            public Tree<T> Left  { get; set; }
+            public Tree<T> Right { get; set; }
+        }
+    }
+}
+
diff --git a/Allgemeines/Threads/Threads/Program.cs b/Allgemeines/Threads/Threads/Program.cs
index 37a927f..f9fb092 100644
--- a/Allgemeines/Threads/Threads/Program.cs
+++ b/Allgemeines/Threads/Threads/Program.cs
@@ -22,6 +22,18 @@ namespace Threads
             Chapter3.Test();
             Chapter4.Test();
             Chapter5.Test();
+            Chapter6 chapter6 = new Chapter6();
+            var tree = new Threads.Chapter6.Tree<int>();
+            var levels = 10;
+            chapter6.FillTree(levels, tree, () => 40);
+
+            Console.WriteLine("Sequential Walk");
+            chapter6.SequentialWalk(tree, (data, level) => Console.WriteLine("Level: {0} Data: {1}", level, data));
+
+            Console.WriteLine("Parallel Walk");
+            // In my case the parallel walk is slower than the sequential one because the tasks are short and
+            // we waste more time creating new threads and synchronizing than running these simple tasks.
+            chapter6.ParallelWalk(tree, (data, level) => Console.WriteLine("Level: {0} Data: {1}", level, data));
         }
     }
 }
diff --git a/Allgemeines/Threads/Threads/Threads.csproj b/Allgemeines/Threads/Threads/Threads.csproj
index e158fea..cd8f300 100644
--- a/Allgemeines/Threads/Threads/Threads.csproj
+++ b/Allgemeines/Threads/Threads/Threads.csproj
@@ -43,6 +43,7 @@ See: http://parallelpatterns.codeplex.com/</Description>
     <Compile Include="Chapter3.cs" />
     <Compile Include="Chapter4.cs" />
     <Compile Include="Chapter5.cs" />
+    <Compile Include="Chapter6.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
 </Project>
\ No newline at end of file
-- 
2.1.4